R. (1) Symbol used to represent an organic group Source: Natural product.

in a chemical formula, for example CH

etc. (2) A free radical (•, R Code: •). (3) The gas

racephedrine. (racemic ephedrine; dl-ephed-

constant, equal to p

/273C. (4) Abbreviation of

rine). C

NO.

Rankine temperature scale.

Properties: Crystals. Mp 79C. Soluble in water, al-

cohol, chloroform, and oils.

Ra. Symbol for radium.

Derivation: Synthetic.

Use: Medicine (also as hydrochloride and sulfate).

See ephedrine.

R-acid. (2-naphthol-3,6-disulfonic acid; ␤-na-

phtholdisulfonic acid).

racking. Experimental cold-stretching of unvul-

canized rubber, whose behavior under stress is

unique among natural materials. A thin, narrow strip

stretched at, for example, 500–600% at 0C will

retain that extension indefinitely after release of

stress as long as the low temperature persists. In this

Properties: Deliquescent, colorless needles. Soluble

state it loses its elasticity and has virtually 100%

in water, alcohol, and ether.

permanent set. It also displays a crystalline X-ray

Derivation: Sulfonation of ␤-naphthol. For details

pattern similar to that of a fiber, in contrast to the

see Schaeffer acid.

amorphous structure of the unstretched state. On

Use: Azo dye intermediate. The disodium salt is used

exposure to room temperature it slowly retracts to its

as a reagent in detection of nitrogen dioxide in the

original length; higher temperature increases its rate

air.

of recovery. Tests made on racked rubber have

showm that crude rubber can be exposed to any

2R acid. See RR acid.

degree of low temperature for any length of time

without impairment of its properties.

racemate. (1) The mixture of two optically active

components that neutralize the optical effect of each

rad. That quantity of ionizing radiation that re-

other. (2) Salt of racemic acid.

sults in the absorption of 100 ergs of energy per gram

of irradiated material, regardless of the source of the

racemic mixture. A mixture of the D and L

radiation. The federal radiation safety standard is 0.5

stereoisomers of an optically active compound.

rem per person per year for nonoccupational expo-

sure, and even this is considered too high by some

racemic substance. A mixture of dextro- and

authorities. Occupational exposure is set at 5 rem

levorotatory optically active isomers in equal

per year.

amounts, the resulting mixture having no rotary

See rem.

power. These mixtures are prefixed by n˜ or dl-.

See dl-.

radiation. Energy in the form of electromagnetic

waves (also called radiant energy, or light). It is

racemization. Conversion, by heat or by chemi-

emitted from matter in the form of photons (quanta),

cal reaction (e.g., enolization) of an optically active

each with an associated electromagnetic wave hav-

compound into an optically inactive form in which

ing frequency (␯) and wavelength (␭). The various

half of the optically active substance becomes its

forms of radiant energy are characterized by their

mirror image (enantiomer). This change results in a

wavelength, and together they compose the electro-

mixture of equal quantities of dextro- and levorota-

magnetic spectrum, the components of which are as

tory isomers, as a result of which the compound does

follows: (1) cosmic rays (highest energy, shortest

not rotate plane-polarized light to either right or left

wavelength), (2) ␥-rays from radioactive disintegra-

since the two opposite rotations cancel each other.

tion of atomic nuclei, (3) X-rays, (4) UV rays, (5)

This is sometimes referred to as external compensa-

visible light rays, (6) infrared, (7) microwave, and

tion, as opposed to the internal compensation exhib-

(8) radio (Hertzian) and electric rays. All these are

ited by meso-compounds.

identical in every way except wavelength, those

See meso-(1); tartaric acid.

having the shortest wavelength being the most pene-

trating. They are not electrically charged and have

racemomycin E. no mass, their velocity of propagation is the same,

CAS: 3484-68-2. mf: C

all display the properties characteristic of light and

Hazard: A poison. have a dual nature (wave-like and corpuscular). In a

1070

1071 RADIOACTIVE WASTE

looser sense the term radiation also includes energy tron-beam radiation. Required are a monomer or

oligomer and a photoninitiator, which induces poly-

emitted in the form of particles that possess mass

merization by free radical formation.

and may or may not be electrically charged, (i.e., ␣

See “Electrocure.”

[positive] and ␤ [negative]) and also neutrons.

Beams of such particles may be considered as

“rays.” The charged particles may all be accelerated

radiation, ionizing. Extremely short-wave-

and the high energy imparted to “beams” in particle

length, highly energetic, penetrating rays of the fol-

accelerators such as cyclotrons, betatrons, synchro-

lowing types: (1) ␥-rays emitted by radioactive ele-

trons, and linear accelerators.

ments and isotopes (decay of atomic nuclei); (2) X-

Radiation is used in medicine in the form of X-rays

rays generated by sudden stoppage of fast-moving

and radioactive isotopes; it is used in industry in

electrons; (3) subatomic charged particles (elec-

many ways, e.g., as vitamin activator, sterilizing

trons, protons, deuterons) when accelerated in a

agent, and polymerization initiator; it is also the

cyclotron or betatron. The term is restricted to elec-

basis of all types of spectroscopic analysis.

tromagnetic radiation at least as energetic as X-rays,

and to charged particles of similar energies. Neu-

trons also may induce ionization.

radiation biochemistry. The study of sub-

Such radiation is strong enough to remove electrons

stances having the ability to protect cells and body

from any atoms in its path, leading to the formation

tissue against the deleterious effects of ionizing radi-

of free radicals. These short-lived but highly reac-

ation. Because one of these effects is to deprive

tive particles initiate decomposition of many organ-

proteins of sulfhydryl (

−

SH) groups necessary for

ic compounds. Thus ionizing radiation can cause

cell division, the injection of compounds rich in this

mutations in DNA and in cell nuclei; adversely af-

radical (notably cysteine) has been successfully

fect protein and amino acid mechanisms; impair or

tried with laboratory animals. Thiourea has been

destroy body tissue; and attack bone marrow, the

found to protect DNA from depolymerization by X-

source of red blood cells. Exposure to ionizing radi-

rays; enzymes containing

−

SH groups inactivated by

ation for even a short period is highly dangerous, and

radiation are reactivated by addition of glutathione.

for an extended period may be lethal. The study of

Some of the other radiochemically induced reac-

the chemical effects of such radiation is called radia-

tions that adversely affect biochemical activity are

tion chemistry or (in the case of body reactions)

(1) formation of hydrogen peroxide (a biological

radiation biochemistry. See radiation, indus-

poison) by free radical mechanism; (2) denaturation

trial.

of proteins; (3) change in substituent groups of ami-

no acids; (4) oxidation of hemoglobin; (5) depoly-

merization of DNA.

radiation hybrid. A hybrid cell containing

See radiation, ionizing. small fragments of irradiated human chromosomes.

Maps of irradiation sites on chromosomes for the

human, rat, mouse, and other genomes provide im-

radiation curing. See radiation, industrial

portant markers, allowing the construction of very

(6).

precise STS maps indispensable to studying multi-

factorial diseases.

radiation, industrial. Chemical or physio-

See sequence tagged site.

chemical changes induced by exposure to various

types and intensities of radiation. (1) Synthesis of

radical. (1) An ionic group having one or more

ethyl bromide from hydrogen bromide and ethylene,

charges, either positive or negative, e.g., OH

−

,NH

using ␣-radiation from cobalt-60. (2) Cross-linking

2−

of such polymers as polystyrene and polyethylene

(2) See free radical; group (2).

with either ␤-or␥- radiation. (3) Vulcanization of

rubber with ionizing radiation. (4) Polymerization

radioactive isotope. See radioisotope.

of methyl methacrylate monomer with cobalt-60 as

source of ␥-rays. Free radical formation is involved

in both cross-linking and polymerization reactions.

radioactive waste. Disposal of waste contain-

This technique is also being applied in the textile ing radioisotopes and of spent nuclear reactor fuel

finishing field for grafting and cross-linking fibers presents a serious problem for which there is as yet

with chemical agents for durable-press fabrics. (5) no completely satisfactory solution. Such wastes

Processing of various foods (cooking, drying, pas- may remain radioactive for thousands of years and

teurizing, etc.) by electromagnetic energy in the can constitute a long-term hazard that is restraining

microwave region of the spectrum; preservation and the development of nuclear-generated electric pow-

sterilization of food products by ionizing radiation er. Safe disposal techniques are being intensively

(␥- and X-rays). The dosage of radiation is strictly studied. Ocean dumping, practiced some years ago,

controlled, and FDA approval is required. Irradia- is no longer permissible. Small amounts of low-lev-

tion is also effective in inhibiting sprouting and el wastes containing radioisotopes can be diluted

preventing insect infestation of stored grains. (6) sufficiently with an inert material to reduce its activ-

Curing or hardening of organic protective coatings ity to an acceptable point. High-level reactor wastes,

(paints, inks) by exposure to infrared, UV, or elec- for example, at Hanford, are stored in concrete tanks

1072RADIOACTIVITY

lined with steel and buried under a foot of concrete lecule, based on its capacity to displace a radioactive

and 5 or 6 ft of soil. Containers of compressed form of the molecule from combination with its

alumina (corundum) have been recommended, as specific antibody.

this material remains impervious to water indefi-

nitely. Storage in the form of calcine (granular solid)

radioisotope. (radionuclide). An isotopic form

and in borosilicate glass is a promising possibility

of an element (either natural or artificial) that exhib-

under active investigation. The DOE has recom-

its radioactivity. Radioisotopes are used as diagnos-

mended disposal in deep geologic formations, al-

tic and therapeutic agents in medicine, in biological

though the heat generated by the radioactivity could

tracer studies, and for many industrial purposes,

cause fracturing of the surrounding rock structures;

from measurement of thickness to initiating poly-

this would admit water that would eventually rise to

merization. Artifical radioisotopes are made by neu-

the surface after being contaminated. A test program

tron bombardment of stable isotopes in a nuclear

involving storage in basalt is being conducted by

reactor.

DOE. Storage in salt formations is under serious

See tracer; isotope.

consideration because they are self-sealing and free

from water.

radium. Ra. Radioactive element of group IIA of

See waste control.

the periodic table, atomic number 88, aw 226.0254,

valence

2. There are 14 radioactive isotopes but

radioactivity. Natural or artificial nuclear trans-

only radium-226 with half-life of 1620 years is us-

formation; discovered by Becquerel in 1895. The

able. Discovered by the Curies in 1898.

energy of the process is emitted in the form of ␣-, ␤-,

Properties: Brilliant-white solid. Mp 700C, bp

or ␥-rays. Thus radium-226 undergoes radioactive

1140C, d 5. Luminescent, turns black on exposure to

decay by the emission of an ␣-particle, and the new

air. Soluble in water with evolution of hydrogen;

product is radon-222. The decay series terminates in

forms water-soluble compounds. Decays by emis-

lead-206. Radioactivity is not affected by the physi-

sion of ␣-, ␤-, and ␥-radiation. Bone-seeking when

cal state or chemical combination of the element.

taken into the body.

The radioactivity of a nuclide is characterized by the

Occurrence: Colorado, Canada, Zaire, France, the

nature of the radiations, their energy, and the half-

former U.S.S.R..

life of the process, i.e., the time required for the

Derivation: Uranium ores (pitchblende and carno-

activity to decrease to one-half of the original. Half-

tite). The method used for isolating radium is similar

lives vary from microseconds to millions of years.

to that developed by Mme. Curie and involves co-

Some radioactive elements occur in nature (radium,

precipitation with barium and lead, chemical separa-

uranium). Radioactivity can be caused artifically in

tion with hydrochloric acid, and further purification

many stable elements by irradiation with neutrons in

by repeated fractional crystallization. The metal is

a nuclear reactor, or by charged particles from an

separated from its salts by electrolysis and subse-

accelerator.

quent distillation in hydrogen. Dry salts are stored in

Amounts of radioactive material are usually ex-

sealed glass tubes, opened regularly by experienced

pressed in units of activity, the rate of radioactive

workers to relieve pressure. The tubes are kept in

decay. The accepted unit is the curie (Ci) and its

lead containers.

metric multiples and fractions, the mega, kilo, milli-,

Hazard: Highly toxic, emits ionizing radiation. Lead

and microcurie. A curie is 3.73 × 10

disintegrations

shielding should be used in storage and handling,

per sec. A common unit is millicuries per millimole.

adequate protective clothing and remote control de-

Packaging and shipment of radioactive materials,

vices are essential. Destructive to living tissue.

which are highly toxic, must be in accord with offi-

Use: Medical treatment for malignant growths, in-

cial requirements. Consult IATA and DOT shipping

dustrial radiography, source of neutrons and radon.

regulations for labeling and other instructions.

See rad; rem.

radium bromide. RaBr

Properties: White crystals, becoming yellow or

radiocarbon. See carbon-14; chemical dating.

pink, radioactive. D 5.79, mp 728C, sublimes at

900C. Soluble in water and alcohol.

radiochemistry. The subdivision of chemistry

Derivation: Freed from the ores as a bromide mixed

that deals with the properties and uses of radioactive

with barium bromide.

materials in industry, biology, and medicine, includ-

Method of purification: Fractional crystallization.

ing tracer research and radioactive waste disposal.

Impurities: Barium salts.

See nuclear chemistry.

Grade: Technical, pure. The purity is determined by

the strength of the ionizing power of the salt, i.e., the

extent to which it causes air to conduct electricity.

radiogenic. Refers to a material produced by

Hazard: As for radium.

radioactive decay. An example is the production of

Use: Medicine (cancer treatment), physical research.

lead from uranium decay.

radioimmunoassay. A sensitive and quantita- radium carbonate. RaCO

tive method for detecting trace amounts of a biomo- Properties: Amorphous radioactive powder; white

1073 RANITIDINE BISMUTH CITRATE

when pure, but sometimes yellow, orange, or pink

Raman spectroscopy. An analytical technique

due to impurities. Insoluble in water. discovered in 1928 by C. V. Raman, an Indian physi-

Available forms: Mixture with barium carbonate.

cist who received the Nobel Prize in Physics.

Hazard: As for radium.

See spectroscopy; photometric analysis.

Ramberg-Backlund reaction. Reaction of ␣-

radium chloride. RaCl

halo sulfones with strong bases to yield alkenes.

Properties: Yellowish-white crystals becoming yel-

low or pink on standing. Radiactive. Mp 1000C, d

ramie. A natural fiber obtained from the stems of

4.91. Soluble in water and alcohol.

Boehmeria nivea, of the hemp family. High wet

Derivation: Freed from the ores as a chloride mixed

strength, absorbent but dries quickly, can be spun or

with barium chloride.

woven. Wears well and has great rot and mildew

Method of purification: Fractional crystallization.

resistance, tensile strength four times that of flax,

Grade: Technical, pure. The purity of radium salts is

elasticity 50% greater than flax.

determined by the strength of their ionizing power,

Source: Taiwan, Egypt, Brazil, Florida.

i.e., the extent to which they cause air to conduct

Hazard: Combustible, not self-extinguishing.

electricity.

Use: High-grade paper (Europe), fabrics (weaving

Hazard: As for radium.

apparel and car seat covers), stern-tube packing in

Use: Medicine (cancer treatment), physical research.

ships, patching water mains (Great Britain).

radium sulfate. RaSO

“Ramrod” [Solutia]. TM for selective preem-

Properties: White crystals when pure, but some-

ergence herbicide available as a wettable powder

times yellow, orange, or pink due to impurities.

(contains 65% 2-chlor-N-isopropylacetanilide) and

Radioactive. Insoluble in acids and water.

granular form (contains 20% 2-chloro-N-isopropy-

Hazard: As for radium.

lacetanilide).

radon.

Ramsay, Sir William. (1852–1916). A Brit-

CAS: 10043-92-2. Rn. Gaseous radioactive ele-

ish chemist born in Scotland who received the Nobel

ment. Atomic number 86; noble gas group of period-

Prize for chemistry in 1904. He participated in the

ic table; aw 222; valences

2, 4, (6); 18 radioactive

discovery of helium, argon, neon, xenon, and kryp-

isotopes, all short-lived. The radon-222 isotope has

ton. Much of his work concerned investigations of

a half-life of 3.8 days, emits ␣-radiation.

inert gases. He was also known for studies in organ-

Properties: Colorless gas. D 9.72 g/L (0C). Soluble

ic, physical, and inorganic chemistry. Ramsay was

in water. Can be condensed to a colorless, transpar-

educated at the Universities of Glasgow, Heidel-

ent liquid (bp −61.8C) and to an opaque, glowing

berg, and Tubingen, and was a Professor at the

solid. The heaviest gas known.

Universities of Bristol and London.

Derivation: Radioactive decay of radium. Radon is

obtained by bubbling air through a radon salt solu-

Ramsbottom coke test. A laboratory test for

tion and collecting the gas plus air.

carbon residue in petroleum products.

Hazard: As for radium.

Use: Medicine (cancer treatment), tracer in leak de-

random primed synthesis. If you have a

tection, flow-rate measurement, radiography, chem-

DNA clone and you want to produce radioactive

ical research.

copies of it, one way is to denature it (separate the

strands), then hybridize to that template a mixture of

raffinate. The portion of an oil that is not dis-

all possible 6-mer oligonucleotides. Those oligos

solved in solvent refining of lubricating oil.

will act as primers for the synthesis of labeled

strands by DNA polymerase (in the presence of

raffinose.

radiolabeled precursors).

CAS: 512-69-6. C

•5H

O. A trisaccharide

composed of one molecule each of

D(+)galactose,

Raney nickel.

D(+)glucose, and D(−)-fructose.

Properties: Dark-gray powder or crystals, pyro-

Properties: White, crystalline powder; sweet taste.

phoric.

D 1.465, mp (anhydrous) 118–119C, bp decom-

Derivation: By leaching the aluminum from an alloy

poses at about 130C, optical rotation +104.5 de-

of 50% aluminum–50% nickel with 25% caustic

grees. Soluble in water; very slightly soluble in alco-

soda solution.

hol. Split by invertase to melibiose and saccharose.

Hazard: Ignites spontaneous in air, store under alco-

Combustible.

hol or water, dangerous fire risk.

Derivation: Hydrolysis of cottonseed meal, from

Use: Catalyst for hydrogenation.

sugar beet concentrates.

Use: Bacteriology, preparation of other saccharides.

ranitidine bismuth citrate.

CAS: 128345-62-0. mf: C

S•C

BiO

rainfall, induced. See nucleation. Hazard: A poison by ingestion.

1074RANKINE

Rankine. A scale of absolute temperature based thulium Tm 69

ytterbium Yb 70

on Fahrenheit degrees. Temperatures on the Ran-

lutetium Lu 71

kine scale are 9/5 (or 1.8) times those on the Kelvin

scale.

The elements 57–62 are known as the cerium sub-

See absolute temperature.

group, and 63–71 as the yttrium subgroup. Yttrium,

atomic number 39, although not a rare-earth ele-

Raoult’s law. The vapor pressure of a substance

ment, is found associated with the rare earths and is

in equilibrium with a solution containing the sub-

separated only with difficulty.

stance is equal to the product of the mole fraction of

Source: Monazite, bastnasite, and related fluocarbo-

the substance in the solution and the vapor pressure

nate minerals as well as minerals of the yttrium

of the pure substance at the temperature of the solu-

group. These ores contain varying percentages of

tion. The law is not applicable to most solutions, but

rare-earth oxides, which are often loosely called rare

is often approximately applicable to a mixture of

earths. Rare earth elements also occur as fission

closely similar substances, particularly the sub-

products of uranium and plutonium.

stance present in high concentration.

Occurrence: (Monazite) India, Brazil, Florida, Car-

olinas, Australia, South Africa; (bastnasite) Califor-

rapeseed. See canola.

nia.

See didymium.

rapeseed meal. The ground press-cake left

from expression of rapeseed oil. Its major use is as

rare-cutter enzyme. See restriction-enzyme

an animal feed ingredient, but the presence of harm-

cutting site.

ful glucosides, which may be goiter-inducing, limits

its application for this purpose. Research efforts are

rare gas. Any of the six gases composing the

being directed to removal of this constituent from

extreme right-hand group of the periodic table,

meal produced in Canada. The meal also has some

namely helium, neon, argon, krypton, xenon, and

use as a fertilizer. If fed to animals, it should be

radon. They are preferably called noble gases or

blended with other feeds.

(less accurately) inert gases. The first three have a

Properties: Pale yellow liquid. Sol in chloroform

valence of 0 and are truly inert, but the others can

and ether.

form compounds to a limited extent.

rapeseed oil. A vegetable oil derived from rape

rare metal. A loose term for the less common

by expression or solvent extraction; it is now pro-

metallic elements. They include the alkaline-earth

duced chiefly in Canada. It is a viscous, brownish

metals (barium, calcium, and strontium), beryllium,

liquid, though when refined it is yellow. D

bismuth, cadmium, cobalt, gallium, germanium,

0.913–0.916, solidifies at 0C, flash p 325F (162C),

hafnium, indium, lithium, boron, silicon, manga-

autoign temp 836F (446C), subject to spontaneous

nese, molybdenum, rhenium, selenium, tantalum,

heating. It is high in unsaturated acids, especially

niobium, tellurium, thallium, thorium, titanium,

oleic, linoleic, and erucic.

tungsten, uranium, vanadium, zirconium, and the

Use: Edible oil for salad dressings, margarine, etc.;

rare earths.

lubricant additive; substitute for soybean oil; soft

soaps; blown oils.

“Rareox” [Grace]. TM for optical quality ceri-

um oxide for high speed polishing.

“Rapi-Cure” [International Specialty].

TM for diluent for radiation curing.

Raschig phenol process. Commercial pro-

cess for the production of phenol by the hydrolysis

rare earth. One of a group of 15 chemically

of chlorobenzene, produced by the chlorination of

related elements in group IIIB of the periodic table

benzene with hydrochloric acid and air.

(lanthanide series). Their names and atomic num-

bers are as follows:

Raschig rings. Short sections of metal tubes.

Use: Packing in distillation towers.

lanthanum La 57

See tower, distillation.

cerium Ce 58

praseodymium Pr 59

Rast method. The melting-point depression

neodymium Nd 60

method often used for the determination of the mo-

promethium Pm 61

lecular weight of organic compounds.

samarium Sm 62

europium Eu 63

rate-limiting step. The slowest step in a meta-

gadolinium Gd 64

bolic pathway.

terbium Tb 65

dysprosium Dy 66

holmium Ho 67

Raticate. TM for 5-(␣-hydroxy-␣-2-pyridylben-

erbium Er 68 zyl)-7-(␣)-2-pyridylbenylidene-5-norbornene-2,3-

1075 REACTION OF SECOND ORDER

dicarboximide. A rodenticide specific for rats, sup-

“Rayox.” TM for titanium dioxide.

posedly nontoxic to other animals or to humans

(U.S. Dept. of Agriculture).

Rb. Symbol for rubidium.

“RBR Revitalizer” [General Graphics].

rauwolfia. The powdered whole root of Rauwol-

TM for a liquid naptha solvent blend.

fia serpentina, found in India and Indonesia. The

plant is of value as a source of alkaloids, especially

RCFs. See refractory ceramic fibers.

reserpine.

Properties: Light-tan to light-brown, bitter, fine,

R&D. Abbreviation for research and develop-

amorphous powder; slight aromatic odor. Sparingly

ment, usually referring to the department or division

soluble in alcohol; very slightly soluble in water.

of a company whose major responsibility is applied

Grade: NF.

research and creative development of new products

Use: Medicine (antihypertensive agent).

and processes.

raw material. (1) The basic material from

RDA. Abbreviation for recommended dietary al-

which one or more useful products are derived, e.g.,

lowances of food requirements, including proteins,

bauxite is the raw material for aluminum, wood for

vitamins and minerals for infants, children, and

paper, rayon, etc.; petroleum for fuels and chemi-

adults, established by the Food and Nutrition Board

cals. (2) As commonly used, the term refers to any

of the National Academy of Sciences—National

ingredient or component of a mixture or product

Research Council. They are revised periodically,

before mixing and processing take place, e.g., fill-

particularly in reference to certain vitamins (C, B

ers, colorants, antioxidants, etc.

and E) and proteins.

See storage (1).

See USRDA.

“Raykrome” [Rayonier]. (lignin sulfonate).

RDGE. See resorcinol diglycidyl ether.

TM for binding and dispersing emulsifiers.

Use: In concrete water reduction, oil-well drilling,

RDX. See cyclonite.

dye dispersing, and road stabilization.

Re. Symbol for rhenium.

␥-ray. See gamma ray.

“ReACt 784” [Hernon]. TM for a two com-

rayon. Generic name for a semisynthetic fiber

ponent, no mix, structural adhesive compound.

composed of regenerated cellulose as well as manu-

factured fibers composed of regenerated cellulose in

reaction, chemical. See chemical reaction.

which substituents have replaced not more than 15%

of the hydrogen of the hydroxyl groups. Rayon was

reaction, fast. A chemical reaction that has a

first made by denitration of cellulose nitrate fibers

heat of activation far in excess of critical energy.

(Chardonnet process), but most rayon is made from

wood pulp by the viscose process. “Regular” vis-

reaction, heterogeneous. A chemical reaction

cose tenacity

2 g/denier; “high-tenacity”

3–6 g/

that takes place on the surfaces between various

denier (tire cord). Elongation 15–30% (dry) and

phases in a heterogeneous system.

20–40% (wet). Swells and weakens when wet.

Moisture regain 11–13%, d 1.50.

reaction injection molding. See injection

Modified rayon is made principally of regenerated

molding.

cellulose and contains nonregenerated cellulose fi-

ber-forming material, for example, a fiber spun from

reaction, mechanism. The manner in which a

viscose containing casein or other protein (ASTM).

chemical reaction proceeds, expressed in a series of

This greatly increases both dry and wet strength and

chemical equations.

also permits mercerization. Rayon is readily dyed by

standard methods.

reaction, nuclear. See nuclear reaction.

Hazard: Flammable, not self-extinguishing, moder-

ate fire risk.

reaction of first order. A chemical reaction

Use: Nonwoven fabrics, surgical dressings, mechani-

in which the velocity of reaction at a given time

cal rubber goods, coated fabrics, felts and blankets,

depends strictly on the amount per unit volume of

blends with cotton for home furnishings, etc.

the reacting substance at the time, all other parame-

See cellophane; acetate fiber; viscose process.

ters staying the same.

rayon coning oil. An oil used to lubricate and reaction of second order. A chemical reac-

reduce the static of yarns wound by a coning ma- tion in which the rate of reaction is in proportion to

chine. Usually composed of mineral oils of low the product of the concentrations of two reacting

viscosity so compounded as to emulsify in water. materials.

1076REACTION ORDER

reaction order. The total of all the orders with recessive gene. A gene which will be expressed

respect to various substances is called the total order only if there are 2 identical copies or, for a male, if

or the order of the reaction. Also when a reaction has one copy is present on the X chromosome.

a rate that is in proportion to some power of the

concentration of one of the reacting substances in-

recipe. A product formula.

volved.

Use: Food industry.

reaction product imaging. A beam of hydro-

reciprocal translocation. When a pair of

gen atoms is crossed with a beam of cold deuterium

chromosomes exchange exactly the same length and

(D) molecules. The ion images appearing on the

area of DNA. Results in a shuffling of genes.

detector are two-dimensional projections of the

three-dimensional velocity distribution of the D

reclaiming. Recovery and reuse of scrap materi-

atom products.

als, either in low percentage in new product manu-

facture or in larger proportions in products in which

reaction step. The reaction where individual

the highest quality is not essential. Among the mate-

parts of the reaction series are identical in nature

rials widely reclaimed in industry are aluminum,

with the primary reaction but differ from it only in

steel, paper, rubber, glass, crankcase oil, greases,

the order that they occur.

etc. Solid materials are comminuted, the contami-

nants being removed with organic solvents or strong

reaction velocity. The rate at which a chemical

alkali solutions (paint from metals, ink from paper,

reaction takes place as measured by the rate of for-

fabric and metals from tires). In the case of cross-

mation of the product or the rate of disappearance of

linked elastomers, more intensive solvent and heat

reactants.

treatment is necessary. The resulting product is used

as an adulterant in low-quality items. Research on

reactive atmosphere. An atmosphere which

high-temperature conversion of scrap rubber to oil,

causes a change in composition of the material im-

with recovery of carbon black and metal inserts,

mersed in it.

indicates that substantial value may be obtained by

this method. Devulcanization by means of micro-

reading frame. When mRNA is translated by

wave radiation is also under development. The term

the cell, the nucleotides are read three at a time. By

reprocessing refers specifically to the recovery of

starting at different positions, the groupings of three

nuclear fuels from reactor waste.

that are produced can be entirely different.

See recycling; reprocessing.

reagent. Any substance used in a reaction for the

recombinant clone. Clone containing recom-

purpose of detecting, measuring, examining, or ana-

binant DNA molecules.

lyzing other substances. High purity and high sensi-

See recombinant DNA technology.

tivity are essential requirements of lab reagents.

Over 8000 reagent chemicals are commercially

recombinant DNA. See genetic engineering;

available.

biotechnology.

See grade.

recombinant DNA molecules. A combina-

“Realox” [ALCOA]. Al

TM for calcined

tion of DNA molecules of different origin that are

aluminas.

joined using recombinant DNA technologies.

Properties: High-purity, reactive alumina.

Use: In the production of high alumina ceramics and

recombinant DNA technology. Procedure

refractories.

used to join together DNA segments in a cell-free

system (an environment outside a cell or organism).

rearrangement. A type of chemical reaction in

Under appropriate conditions, a recombinant DNA

which the atoms of a single compound recombine,

molecule can enter a cell and replicate there, either

usually under the influence of a catalyst, to form a

autonomously or after it has become integrated into

new compound having the same molecular weight

a cellular chromosome.

but different properties. Thus ammonium cyanate in

solution will rearrange to form urea, in which the

recombination. The process by which progeny

four hydrogen atoms are equally distributed be-

derive a combination of genes different from that of

tween the two nitrogen atoms: NH

OCN →

either parent. In higher organisms, this can occur by

(NH

)

C==O. Many such rearrangements have been

crossing over.

named for their discoverers, e.g., Beckmann rear-

See crossing over; mutation.

rangement.

See Wohler.

reconstitution. In food technology, restoration

Reaumur. A temperature scale in which 0 is the of a dehydrated food product to its original edible

freezing point of water and 80 is its boiling point. condition by adding water to it at the time of use. It is

1077 REDUCING SUGAR

also called rehydration.

red lead. See lead oxide, red.

See dehydration.

red mud. A by-product sludge from aluminum

rectification. The enrichment or purification of ore processing; it contains 30–60% iron oxide. It

the vapor during the distillation process by contact may be used for steel making.

and interaction with a countercurrent stream of liq-

uid condensed from the vapor.

red ocher. See ocher.

See reflux.

red oil. A commercial grade of oleic acid com-

prising 70% oleic and 15% each of linoleic and

“RectorSeal” [Rectorseal]. TM for a NSF

stearic acids.

certified pipe repair kit,

redox. Short form of the term oxidation-reduc-

recycling. The practice of returning a portion of

tion,asinredox reactions, redox conditions, etc.

the reaction products to the start of the system, either

See oxidation.

for the purpose of more efficient conversion of un-

reacted components or to reuse auxiliary materials

redox reaction. An oxidation-reduction reac-

that remain unchanged during processing. In the

tion.

petroleum refining industry, some of the product

stream may be recycled and blended with the fresh

input materials to obtain a product of maximum

redox pair. An electron donor and its corre-

value. In some industries, processing wastes are sponding oxidized form; for example, NADH and

recycled. NAD+.

See reclaiming; reprocessing.

red oxide. See iron oxide red.

red acetate. See aluminum diacetate.

red phosphorus. See phosphorus.

red algae. See algae, red.

red tide. Yellow-to-reddish discoloration of sea-

red arsenic. See arsenic disulfide. water due to rapid multiplication of various species

of plantlike microorganisms, called dinoflagellates,

which occurs seasonally in areas of warm water,

red brass. Copper-zinc (brass) alloys character-

especially off the coast of Florida and occasionally

ized by their red color and high copper content. The

as far north as New England. Some, though by no

term is used for several different types of brass. One

means all, of the species are poisonous. Concentra-

ASTM classification permits 2–8% zinc, tin less

tion of these organisms (phytoplankton) may be as

than zinc, and lead less than 0.5%. Other alloys

high as 10

units/L. The shelfish are lethal to free-

referred to as red brass include those with 75–85%

swimming fish. Shellfish are unharmed by them, but

copper, up to 20% zinc, and usually very small

are able to store and concentrate the toxin which

amounts of lead and tin. In one alloy possessing

causes paralytic poisoning when they are eaten by

good machining qualities, the lead content may be as

humans. So potent is this poison that death may

high as 10%, the tin as high as 5%.

result from ingestion of milligram amounts.

Red brasses are widely used for decorative purposes

and in plumbing and piping because of their resis-

tance to atmospheric corrosion and dezincification.

reduced states. See corresponding states.

Red Dye No. 2. See amaranth; FD&C reductant. See reducing agent.

colors.

reducing agent. (reductant). The electron do-

red glass. A soda-zinc glass containing a small nor in a redox reaction.

amount of cadmium and 1% selenium. Red may also

be obtained by using cuprous oxide or gold chloride,

reducing end. The end of a polysaccharide hav-

the latter usually in the form of purple of Cassius.

ing a terminal sugar with a free anomeric carbon; the

terminal residue can act as a reducing sugar during

red iron oxide. See iron oxide, red. the portion of time it exists in the open-chain form.

red iron trioxide. See ferric oxide. reducing equivalent. A general term for an

electron or an electron equivalent, usually in the

form of a hydrogen atom or a hydride ion.

red lake C. One of a family of organic acid azo

pigments prepared by coupling the diazonium salt of

o-chloro-m-toluidine-p-sulfonic acid with ␤-naph-

reducing sugar. A sugar in which the anomeric

thol. Both sodium and barium salts of the parent dye carbon is not involved in a glycosidic bond and can

are used. therefore undergo oxidation during the portion of

Use: Plastics, rubber products, printing inks. time it exists in the open-chain form.

1078REDUCTION

reduction. (1) The opposite of oxidation. Reduc- Reformatskii reaction. Condensation of car-

tion may occur in the following ways: (a) acceptance bonyl compounds with organozinc derivatives of ␣-

of one or more electrons by an atom or ion, (b) halo esters to yield ␤-hydroxy esters.

removal of oxygen from a compound, (c) addition of

hydrogen to a compound. (2) Size reduction of ma-

reforming. Decomposition (cracking) of hydro-

terials.

carbon gases or low-octane petroleum fractions by

See (1) oxidation; (2) comminution.

heat and pressure, either without a catalyst (thermo-

forming) or with a specific catalyst (molybdenum,

“Reductone” [Olin]. TM for sodium hydrosul- platinum). The latter method is the more efficient

fite. and is used almost exlcusively in the U.S. The chief

CAS: 7775-14-6. cracking reactions are (1) dehydrogenation of cyclo-

Grade: Solution. hexanes to aromatic hydrocarbons; (2) dehydrocy-

Use: Continuous vat dyeing and afterscouring; clization of certain paraffins to aromatics; (3) isom-

bleaching of clay, ground wood, and thermal me- erization, i.e., conversion of straight-chain to

chanical pulp. branched-chain structures, as octane to isooctane.

These result in substantial increase in octane num-

ber. Steam reforming of natural gas is an important

Reed reaction. Photochemical sulfonation of

method of producing hydrogen by the reaction CH

paraffins and cycloparaffins by sulfur dioxide and

O → 3H

+ CO; steam reforming of naphtha is

chlorine under irradiation with UV light.

used to produce synthetic natural gas.

See hydroforming; “Platforming.”

refined mineral oil. See dormant oil.

“Refractaloy” [Westinghouse]. TM for a

refined bleached shellac. See shellac,

nickel-cobalt-chromium-molybdenum-iron alloy.

bleached, wax-free.

Type 26 is a precipitation-hardenable material using

titianum as the hardening agent and having high

refinery gas. A mixture of hydrocarbon gases

strength, high ductility, and corrosion resistance up

(and often some sulfur compounds) produced in

to 1450F.

large-scale cracking and refining of petroleum. The

Use: Gas turbine discs, bolting, and blading are typi-

usual components are hydrogen, methane, ethane,

cal applications.

propane, butanes, pentanes, ethylene, propylene,

butenes, pentenes, and small amounts of other com-

refraction. The change in direction (apparent

ponents such as butadiene.

bending) of a light ray passing from one medium to

Use: Source of raw material for petrochemicals,

another of different density, as from air to water or

high-octane gasoline, and organic synthesis of al-

glass. The ratio of the sine of the angle of incidence

cohols.

to the sine of the angle of refraction is the index of

refraction of the second medium. Index of refraction

refining. Essentially a separation process where-

of a substance may also be expressed as the ratio of

by undesirable components are removed from vari-

the velocity of light in a vacuum to its velocity in the

ous types of mixture to give a concentrated and

substance. It varies with the wavelength of the inci-

purified product. Such separation may be effected

dent light, temperature, and pressure. The usual light

(1) mechanically, by pressing, centrifuging, filter-

source is the D line of sodium, the standard tempera-

ing, etc.; (2) by electrolysis; (3) by distillation, sol-

ture being 20C, the expression of refractive index is

vent extraction, or evaporation; and (4) by chemical

20/D.

reaction. One or more of these operations is applied

to (1) food products, (2) petroleum, (3) lubricating

refractive. Descriptive of a substance having a

oils, and (4) metals. As regards petroleum, refining

high refractive index.

is generally understood to include not only fraction-

al distillation of crude oils to naphthas, low-octane

refractive index. See refraction.

gasoline, kerosene, fuel oil, and asphaltic residues,

but also the processes involved in thermal and cata-

lytic cracking (hydroforming, reforming, etc.) for

refractometer. A device for checking the index

production of high-octane gasoline. of refraction.

reflux. In distillation processes in which a frac- refractory. (1) An earthy, ceramic material of

tionating column is used, the term reflux refers to the low thermal conductivity that is capable of with-

liquid that has condensed from the rising vapor and standing extremely high temperature (1650–2200C)

been allowed to flow back down the column toward without essential change. There are three broad

the still. As it does so, it comes into intimate contact groups of these: (a) acidic (silica, fireclay), (b) basic

with the rising vapor, resulting in improved separa- (magnesite, dolomite), and (c) amphoteric (alumina,

tion of the components. The separation resulting carbon, and silicon carbide). Their primary use is for

from contact of the countercurrent streams of vapor lining steel furnaces, coke ovens, glass lehrs, and

and liquid is called rectification or fractionation. other continuous high-temperature applications.

1079 REINECKE SALT

They are normally cast in the form of brick and are

regeneration. (1) Restoration of a material to its

sometimes bonded to assure stability. The outstand- original condition after it has undergone chemical

ing property of these materials is their ability to act

modification necessary for manufacturing purposes.

as insulators. The most important are fireclay (alu-

The most common instance is that of cellulose for

minum silicates), silica, high alumina (70–80%

rayon production. The wood pulp used must first be

), mullite (clay-sand), magnesite (chiefly

converted to a solution by reaction with sodium

MgO), dolomite (CaO-MgO), forsterite (MgO-

hydroxide and carbon disulfide; in this form (cellu-

sand), carbon, chrome ore–magnesite, zirconia, and

lose xanthate) it can be extruded through spinner-

silicon carbide. (2) Characterizing the ability to

ettes. After this operation it is regenerated to cellu-

withstand extremely high temperature, e.g., tung-

lose by passing it through acid (viscose process).

sten and tantalum are refractory metals, clay is a

Collagen can also be regenerated by acid treatment

refractory earth, ceramics are refractory mixtures.

after it has been purified for use in food products by

alkaline solution.

(2) Renewal or reactivation of a catalyst that has

refractory ceramic fibers. (RCFs). Man-

accumulated reaction residues such as coke, usually

made insulating fibers.

accomplished by passage of steam or reducing gases

Use: To replace asbestos in coke ovens and industrial

over the catalyst bed.

furnaces.

(3) Replenishing the sodium ions of a zeolite or

similar ion-exchange agent by treatment with sodi-

“Refrasil” [Carborundum]. TM for a group

um chloride solution. Molecular sieves are regener-

of materials having outstanding high-temperature

ated by heat removal of the water (200C), followed

resistance. Composed of white, vitreous fibers hav-

by treatment with an inert gas.

ing up to 99% silicon dioxide content.

Available forms: Bulk fiber, batt, cloth, tape, sleev-

regulatory enzyme. An enzyme which can be

ing, yarn, cordage, and flakes.

regulated by allosteric mechanisms or by covalent

Use: Aircraft and missile ablative composites; indus-

modification.

trial insulation and filtration applications; protective

welding shield for spark and slag containment.

regulatory gene. A gene that gives rise to a

product involved in the regulation of the expression

“Refrax” [Carborundum]. TM for silicon ni-

of another gene. An example would be the gene

tride–bonded silicon carbide refractories. Available

coding for cro, a repressor protein.

in brick and precision-formed shapes and parts.

Use: Brazing and furnace fixtures; pumps and pump

regulatory region or sequence. A DNA

parts handling corrosive, abrasive slurries; rocket

base sequence that controls gene expression.

motor components; spray nozzles; burners; pyrome-

ter protection tubes; sinker assemblies in wire alu-

regulatory sequence. A DNA sequence in-

minizing; bolts and nuts; valve parts; aluminum-

volved in regulating the expression of a gene.

melting furnace linings and parts; conveyor parts.

regulon. A group of genes that are coordinately

refrigerant. Any substance that by undergoing a

regulated.

change of phase (solid to liquid or liquid to vapor)

lowers the temperature of its environment because

rehydration. See reconstitution.

of its latent heat. Melting ice, with latent heat of 80

calories per gram removes heat and exerts a consid-

Reichert-Meissl number. A measure of vola-

erable cooling effect. Most commercial refrigerants

tile, soluble fatty acids derived under arbitrary con-

are liquids whose latent heat of vaporization results

ditions.

in cooling. Ammonia, sulfur dioxide, and ethyl or

methyl chloride were once widely used. The flam-

Reich process. A method of purifying carbon

mablity and toxicity of these compounds led to a

dioxide produced in fermentation. The small

search for safer refrigerants that resulted in the dis-

amounts of organic impurities are oxidized and ab-

covery of halogenated hydrocarbons, especially

sorbed, and the gas is then dehydrated with chem-

fluorocarbons, which are nonflammable. Under var-

icals.

ious trademarks, these are now generally used for

domestic refrigeration and air-conditioning. Ice and

Reimer-Tiemann reaction. Reaction for the

circulating brine are still used for preservation of

formation of phenolic aldehydes by heating a phenol

fish at sea, and ammonia systems are operated for

with chloroform in the presence of alkali.

seafood storage in warehouses.

reineckate. Tetrathiocyanato diammino chromi-

refrigerant 112a. See 1,1,2-tetrachloro-2,2-

um compound.

difluoroethane.

Reinecke salt. (ammonium tetrathio-

regenerated cellulose. See cellophane. cyanodiammonochromate; ammonium reinec-

1080REINFORCED PLASTIC

kate).

Reissert indole synthesis. Condensation of

CAS: 19441-09-9. NH

[Cr(NH

)

(SCN)

]•H

an o-nitrotoluene with oxalic ester, reduction to the

Properties: Dark-red crystals or crystalline powder.

amine, and cyclization to the indole.

Moderately soluble in cold water; soluble in hot

water and alcohol, decomposes in aqueous solution.

Reissert reaction. Formation of 1-acyl-2-cya-

Derivation: From fusion of ammonium thiocyanate

no-1,2-dihydroquinoline derivatives (Reissert com-

with ammonium dichromate.

pounds) by reaction of acid chlorides with quinoline

Use: Precipitating agent for organic bases such as

and potassium cyanide; hydrolysis of these com-

choline, amines, for certain amino acids; reagent for

pounds yields aldehydes and quinaldic acid.

mercury.

relative error. Ratio of absolute error to exact

value.

reinforced plastic. A composite structure com-

prising of a thermosetting or thermoplastic resin and

relaxation time. A measure of the rate at which

fibers, filaments, or whiskers of glass, metal, boron,

a disequilibrium distribution decays toward an equi-

or aluminum silicate. Unless otherwise indicated,

librium distribution. The electron relaxation time in

this term refers to fiberglass-reinforced plastic

a metal, for example, describes the time required for

(FRP).

a disequilibrium distribution of electron momenta

Properties: Exceptionally high strength, good elec-

(e.g., in a flowing current) to decay toward equilibri-

trical resistivity, weather and corrosion resistance,

um in the absence of an ongoing driving force and

low thermal conductivity, and low flammability.

can be interpreted as the mean time between scatter-

Derivation: Basic acid glass in the form of fiber

ing events for a given electron.

(0.0005 inch), strands of 50–200 fibers, filaments, or

woven fabric are coated by passing through a bath of

relaxin.

molten resin, which acts as a binder. The assembly

CAS: 9002-69-1.

can be either compression- or injection-molded.

Hazard: A poison. A reproductive hazard.

Large, high-strength parts are made by filament

Use: Hormone.

winding. Resins used are polyester, epoxy, pheno-

lic, polypropylene, polystyrene, nylon, polycarbo-

release. (1) Separation of a cured or baked prod-

nate, and polyphenylene oxides.

uct from the metal mold or pan in which it is formed.

Use: Automotive body components, ablative coat-

Common release agents for rubber and plastics are

ings on rockets and space vehicles, appliances (air-

waxy or fatty materials such as paraffin and tallow;

conditioning and refrigerator cases), electrical

vegetable oils are used in the baking industry. Such

equipment, oil-well piping and tubing, large-diame-

materials are collectively called abherents.

ter pipe, industrial piping systems, chemical storage

(2) Gradual diffusion of an active ingredient through

and mixture tanks, unitized cargo containers, marine

a permeable or soluble coating. Pelleted products

equipment, pressure vessels, prefabricated building

such as fertilizers and medicinals are often covered

panels and other structural components, blades for

with a layer of a substance that permits slow and

wind machines.

uniform escape of the active principle. Sulfur is used

See glass fiber; composite; fiber; whiskers.

to coat controlled-release fertilizers; gelatin and

similar materials serve the same purpose in pharma-

ceuticals.

reinforcing agent. (1) One of numerous fine

powders used in rather high percentages to increase

release factors. See termination factors.

the strength, hardness, and abrasion resistance of

rubber, plastics, and flooring compositions. The re-

releasing factors. Hypothalamic hormones that

inforcing effect is in general a function of the parti-

stimulate release of other hormones by the pituitary

cle size of the powder. The finest of all is channel

gland. For example, Luteinizing Hormone Releas-

carbon black, whose surface area may be as great as

ing Hormone (LHRH)

18 acres per pound. Other widely used reinforcing

agents are thermal and furnace blacks, magnesium

rem. The unit of radiation dose equivalent, the

carbonate, zinc oxide, hard clay (kaolin), and hyd-

dosage in rads multiplied by a factor representing

rated silicas. Though some reinforcing agents have

the different biological effects of various types of

positive coloring properties, the term should not be

radiation. The Federal radiation safety standard is

used as a general synonym for pigment.

0.5 rem per person per year for non-occupational

(2) Fibers, fabric, or metal insertions in plastics,

exposure, and even this is considered too high by

rubber, flooring, etc., for the purpose of imparting

some authorities. Occupational exposure is set at 5

impact strength and tear resistance. See pigment;

rem per year.

filler; whiskers.

See rad; dosimetry; radiation.

Reinsch test. A test for detecting small amounts Remsen, Ira. (1846–1927). An American

of arsenic, silver, bismuth, and mercury. chemist born in New York. He began his career in

1081 REPLICATION

medical practice but abandoned it for chemistry and liquids, or solids (gustatory). Standard repellents for

mosquitos, ticks, etc., are citronella oil, dimethyl

went to Germany to study. He received his doctorate

phthalate, n-butylmesityl oxide oxalate, DEET, and

in chemistry from the University of Gottingen in

2-ethyl hexanediol-1,3. Actidione is the most effec-

1870. Returning to the U.S. he taught physics and

tive rodent repellent, but is too toxic and too costly to

chemistry at Williams and was later invited to join

use. Thiuram disulfide, amino complexes with trini-

the staff of Johns Hopkins University where he be-

trobenzene, and hexachlorophene are successfully

came head of the department of chemistry. There he

used. Copper naphthenate and lime/sulfur mixtures

established the first graduate curriculum in chemis-

protect vegetation against rabbits and deer. Shark

try in the U.S. based on the system then in use in

repellents are copper acetate or formic acid mixed

Germany. In 1879, saccharin was discovered in his

with ground asbestos. Bird repellents are chiefly

research laboratory. He wrote several widely used

based on taste, but this sense varies widely with the

textbooks and founded the American Journal of

type of bird so that generalization is impossible. ␣-

Chemistry which later merged with JACS. He was

Naphthol, naphthalene, sandalwood oil, quinine,

President of Johns Hopkins from 1901 to 1912, and

and ammonium compounds have been used, with no

is recognized as one of the great teachers of chem-

uniformity of result.

istry.

See fumigant. (2) A substance that, because of its

physicochemical nature, will not mix or blend with

renaturation. Refolding of a denatured protein

another substance. All hydrophobic materials have

so as to restore native structure and protein function.

water-repellent properties due largely to differences

in surface tension or electric charges, e.g., oils, fats,

rendering. The procedure that separates fats

waxes, and certain types of plastics. Silicone resin

from protein connective tissue and other water-in-

coatings can keep water from penetrating masonry

soluble materials by treating small pieces of animal

by lining the pores, not by filling them; they will not

matter with hot water or steam.

exclude water under pressure.

renewable resources. See biomass; waste

control; gasohol.

replacement. See substitution.

“Renite” [Renite]. TM for a series of high-tem-

perature lubricants, swabbing compounds, release

replication. (1) Making a reverse image of a

agents, and automatic spray equipment for hot-

surface by means of an impression on or in a recep-

forming glass, hot-working metals, and the lubrica-

tive material; usually applied to microscopic tech-

tion of oven conveyer chains and bearings.

niques for obtaining plastic replicas of observed

Use: Glassware products, forging, extrusions and die

objects. (2) In biochemistry, the term refers to repro-

castings; provides lubrication for conveyer chains

duction of the DNA molecule, which is composed of

and bearings in bakery and brick industries.

two interlocking chains of nucleotides (the double

helix structure elucidated by Watson and Crick in

rennet. See rennin.

1953). It reproduces itself by forming two identical

daughter molecules, each of which receives one of

rennin. (rennase; chymosin).

the two chains of the original molecule, the other in

CAS: 9001-98-3. A digestive enzyme secreted by

each case being synthesized from nucleic acids by

the glands of the stomach and causes curdling of

enzymes (DNA polymerases). In the oversimplified

milk. It has the power of coagulating 25,000 times

drawing below the solid lines are the strands of the

its own weight of milk.

original molecule, and the broken lines are the syn-

Properties: Yellowish-white powder or as yellow

thesized strands:

grains or scales; characteristic slightly salty taste;

peculiar odor. Slightly hygroscopic; partially solu-

ble in water and dilute alcohol.

Derivation: From the glandular layer (inner lining)

of the true stomach of the calf. It has been made

experimentally by gene-splicing techniques.

Grade: Rennet is the dried commercial extract con-

taining the rennin.

Use: Pharmacy, cheese making, coagulation of ca-

sein for plastics, food additive.

repeat sequences. The length of a nucleotide

sequence that is repeated in a tandem cluster.

The chemical mechanisms in replication are more

repellent. (1) A substance that causes an insect or complex than previously thought; 12–15 proteins

animal to turn away from it or reject it as food. are involved as well as several enzymes. See

Repellents may be in the form of gases (olfactory), deoxyribonucleic acid; genetic code.

1082REPLISOME

replisome. The multiprotein complex that pro- Purex process is the accepted procedure used for this

motes DNA synthesis at the replication fork. purpose. The spent fuel is dissolved in nitric acid;

separation is effected by solvent extraction with

tributyl phosphate, ion-exchange reactions, and pre-

reporter gene. See marker.

cipitation. The reclaimed uranium-235 and plutoni-

um are sent to fuel fabrication plants for reuse. The

Reppe process. Any of several processes in-

fission product waste is evaporated and stored. An-

volving reaction of acetylene (1) with formaldehyde

other method, called the Civex process, has been

to produce 2-butyne-1,4-diol which can be convert-

proposed to prevent theft of plutonium; here the

ed to butadiene; (2) with formaldehyde under differ-

mixture of waste products, uranium isotopes, and

ent conditions to produce propargyl alcohol and,

plutonium is not separated. Since its plutonium con-

from this, allyl alcohol; (3) with hydrogen cyanide

tent is only 20% it could not be used for weapons; the

to yield acrylonitrile; (4) with alcohols to give vinyl

mixture is suitable for fast breeder reactors. Serious

ethers; (5) with amines or phenols to give vinyl

radiation hazards are involved in reprocessing and

derivatives; (6) with carbon monoxide and alcohols

require use of appropriate shielding and remote-

to give esters of acrylic acid; (7) by polymerization

control handling procedures. Storage of the radioac-

to produce cyclooctatetraene; and (8) with phenols

tive waste also presents a long-range problem that

to make resins. The use of catalysts, pressures up to

has not yet been satisfactorily solved. There are no

30 atm, and special techniques to avoid or contain

commercial reprocessing plants operational in the

explosions are important factors in these processes.

U.S., though there are several in Europe.

See acetylene.

See radioactive waste; breeder.

repetitive DNA. Sequences of varying lengths

reprography. A coined name for the technique

that occur in multiple copies in the genome; it repre-

of reproducing drawings, blueprints, and typograph-

sents much of the human genome.

ic matter by the use of photosensitized papers, or

polyester sheeting, which may be coated with diazo

repressible enzyme. An enzyme whose syn-

dyes. The process has broad potential in the photo-

thesis is inhibited when its reaction product is readi-

copying field and in communications technology. It

ly available to the cell. Occurs only in bacteria.

involves colloid and surface chemistry, ink-paper

interactions, and unusual imaging techniques.

repression. A decrease in the expression of a

gene in response to a regulatory protein.

Research octane number (RON). See oc-

tane number.

repressor. The protein that binds to the regulato-

ry sequence of a gene, blocking its transcription.

resene. The unsaponifiable component of rosin

and other natural resins.

reprocessing. Treatment of spent nuclear reactor

fuel to recover the unconsumed uranium-235 and

plutonium by separating them from each other and

reserpine.

from the fission products formed in the reactor. The CAS: 50-55-5.

Properties: White or pale-buff to slightly yellowish; Hazard: Carcinogen in animals, potential cancer risk

in humans.

odorless powder; darkens slowly on exposure to

Use: Antihypertensive agent, tranquilizer.

light and darkens more rapidly in solution. Mp

264–265C (decomposes). Insoluble in water; slight-

“Resicure” [Atofina]. TM for a series of epoxy

ly soluble in alcohol; soluble in chloroform and

curing agents.

benzene.

Derivation: From Rauwolfia serpentina.

residual oil. A liquid or semiliquid product re-

Grade: USP.

sulting from the distillation of petroleum and con-

1083 RESIN, SYNTHETIC

taining largely asphaltic hydrocarbons. Also known sticky below the glass transition point. Most are

as asphaltum oil, liquid asphalt, black oil, petroleum soluble in alcohols, ethers and carbon disulfide, and

tailings, and residuum. Combustible. insoluble in water. The best known of these are rosin

Use: Roofing compounds, hot-melt adhesives, fric- and balsam, obtained from coniferous trees; these

tion tape, sealants, heating oil for large buildings, have a high acid content. Of more remote origin are

factories, etc. such resins as kauri, congo, dammar, mastic, sand-

See fuel oil. rac, and copal. Their use in varnishes, adhesives, and

Note: Gasoline of 94 octane can be produced from printing inks is still considerable, though diminish-

residual oil in a high-temperature catalytic process, ing in favor of synthetic products. (2) Miscellaneous

thus increasing the yield of gasoline from a barrel of types: shellac, obtained from the secretion of an

crude by 33% when full-scale production is Indian insect, is still in general use as a transparent

achieved. coating; amber is a hard, polymerized resin that

occurs as a fossil; ester gum is a modified rosin;

amorphous sulfur is considered an inorganic natural

residue. A single unit within a polymer, for exam-

resin; liquid resins, sometimes called resinoids, are

ple, an amino acid within a polypeptide chain.

represented by linseed and similar drying oils.

See gum, natural (note); resin, synthetic (note).

“Resimene” [Solutia]. TM for melamine and

ureaformaldehyde resins. Supplied in organic liquid

solutions. The melamine is also available in water-

resinoid. Any thermosetting synthetic resin, ei-

alcohol and soluble, spray-dry powders.

ther in its initial temporarily fusible state or its final

Use: Paint, varnish, lacquer for automobiles, ma-

infusible state (ASTM). Heat-bodied linseed oil,

chinery, appliances, construction, electronics, mis-

partially condensed phenol-formaldehyde and the

siles, chemicals, pulp and paper.

like are also considered resinoids.

resin. A semisolid or solid complex amorphous

resinol. A coal tar distillation fraction containing

mix of organic compounds.

phenols. It is the fraction soluble in benzene but

Properties: It has no definite melting point and no

insoluble in light petroleum, obtained by solvent

tendency to crystallize.

extraction of low-temperature tars or similar materi-

Derivation: Resins can be from animal, vegetable, or

als. Resinols are very sensitive to heat and oxidation.

synthetic origins.

resin, synthetic. A manufactured high polymer

resinamine. C

. Alkaloid from certain

resulting from a chemical reaction between two (or

species of Rauwolfia.

more) substances, usually with heat or a catalyst.

Properties: White or pale-buff to cream-colored,

This definition includes synthetic rubbers and sili-

crystalline powder; odorless; darkens slowly on ex-

cones (elastomers), but excludes modified, water-

posure to light, more rapidly when in solution. Mp

soluble polymers (often called resins). Distinction

238C (in vacuo). Partially soluble in organic sol-

should be made between a synthetic resin and a

vents; insoluble in water.

plastic; the former is the polymer itself, whereas the

Use: Medicine (antihypertensive).

latter is the polymer plus such additives as filters,

colorant, plasticizers, etc.

resinate. A salt of the resin acids found in rosin.

The first truly synthetic resin was developed by

They are mixtures rather than pure compounds.

Baekeland in 1911 (phenol-formaldehyde). This

Use: See soap (2).

was soon followed by a petroleum-derived product

called coumarone-indene, which did indeed have

resiniferatoxin.

the properties of a resin. The first synthetic elasto-

CAS: 57444-62-9. mf: C

mer was polychloroprene (1931) originated by

Hazard: A poison.

Nieuwland and later called neoprene. Since then

many new types of synthetic polymers have been

resin, ion-exchange. See ion-exchange resin.

synthesized, perhaps the most sophisticated of

which are nylon and its congeners (polyamides, by

resin, liquid. An organic, polymeric liquid that,

Carothers), and the inorganic silicone group (Kip-

when converted to its final state for use, becomes

ping). Other important types are alkyds, acrylics,

solid (ASTM). Example: linseed oil, raw or heat-

aminoplasts, polyvinyl halides, polyester, epoxies,

bodied (partially polymerized).

and polyolefins.

See drying oil; resinoid.

In addition to their many applications in plastics,

textiles, and paints, special types of synthetic resins

resin, natural. (1) Vegetable-derived, amor- are useful as ion-exchange media. See “Cumar”;

phous mixture of carboxylic acids, essential oils, plastic; paint; fiber; film; elastomer.

and terpenes occurring as exudations on the bark of Note: Because the term resin is so broadly used as to

many varieties of trees and shrubs. They are com- be almost meaningless, it would be desirable to

bustible, electrically nonconductive, hard and glas- restrict its application to natural, organo-soluble,

sy with conchoidal fracture when cold, and soft and hydrocarbon-based products derived from trees and

1084RESIST

shrubs. But in view of the tendency of inappropriate tum mechanical considerations (i.e., the wave func-

tions of electrons); it is used to describe or express

terminology to “gel” irreversibly, it is a losing battle

the true chemical structure of certain compounds

to attempt to replace “synthetic resin” with the more

that cannot be accurately represented by any one

precise “synthetic polymer.”

valence-bond structure. It was originally applied to

See gum, natural (note).

aromatic compounds such as benzene, for which

there are many possible approximate structures,

resist. A material that will prevent the fixation of

none of which is completely satisfactory.

dye on a fiber, thus making color designs and pattern

See benzene.

prints possible. The resist may act mechanically, as a

The resonance concept indicates that the actual mo-

wax, resin, or gel that prevents absorption of the dye

lecular structure lies somewhere between these vari-

or its accompanying mordant. Citric acid, oxalic

ous approximations, but is not capable of objective

acid, and various alkalies are among the more com-

representation. This idea can be applied to any mole-

mon resists of the chemical type.

cule, organic or inorganic, in which an electron pair

bond is present. The term resonance hybrid denotes

resistor composition. A specially treated,

a molecule that has this property. Such molecules do

semiconducting, metal powder compounded with

not vibrate back and forth between two or more

glass binders and temporary organic carriers. Can be

structures, nor are they isotopes or mixtures; the

applied to glass or ceramic surfaces by stenciling,

resonance phenomenon is rather an idealized ex-

spraying, brushing, or dipping; firing range

pression of an actual molecule that cannot be accu-

704–760C. Compositions can be blended with

rately pictured by any graphic device.

members of the same series to produce intermediate

(2) In the terminology of spectroscopy, resonance is

resistance values. Fired resistors have good repro-

the condition in which the energy state of the inci-

ducibility, low temperature and voltage coefficients,

dent radiation is identical with that of the absorbing

and stability to abrasion, moisture, and relatively

atoms, molecules or other chemical entities. Reso-

high (125C) ambient temperature.

nance is applied in various types of instrumental

Use: To produce fired-on resistor components for

analysis such as nuclear resonance absorption and

electronic circuits.

nuclear magnetic resonance. See absorption

spectroscopy.

resite. See C-stage resin.

Note: The multiple meanings of nucleus and reso-

nance can be a source of confusion, especially when

resitol. See B-stage resin.

these terms are closely associated, as in nuclear

magnetic resonance and resonance of a molecular

“Resmetal” [Borden]. TM for a resin-metal

nucleus. In the first of these expressions, nucleus is

composition that when catalyzed converts to metal-

used in the sense of (1) under “nucleus”, and reso-

like solid. Recommended for mold making, patch-

nance in sense of (2) under “resonance”. In the

ing, forming, and general repair of metal surfaces

second expression, nucleus is used in the sense of (3)

and objects.

under “nucleus” and resonance in the sense of (1)

under resonance.

resol. See A-stage resin.

resorcinol. (resorcin; m-dihydroxybenzene; 3-

resolution. Degree of molecular detail on a phys-

hydroxyphenol).

ical map of DNA, ranging from low to high.

CAS: 108-46-3. C

(OH)

See resolving power.

resolving power. The extent to which a lens can

distinguish small particles and minute distances,

i.e., fine structure. The human eye can resolve ob-

jects of 1/250th inch (100 microns) in any dimen-

sion. The compound microscope has a resolving

power of 0.5 micron; an electron microscope can

Properties: White crystals, becoming pink on expo-

resolve fine structure as small as 5 A

, that is, in the

sure to light when not perfectly pure; sweet taste. D

molecular range. Two factors determine resolving

1.2717, mp 110.7, bp 281C, flash p 261F (127C),

power, the wavelength of the radiation utilized and

autoign temp 1126F (607C). Soluble in water, alco-

the focal depth of the lens. The resolving power of a

hol, ether, glycerol, benzene, and amyl alcohol;

microscope is much more important than its ability

slightly soluble in chloroform. Combustible.

to magnify, for no magnification, however large,

Derivation: By fusing benzene-m-disulfonic acid

can add detail to an image that was not first dis-

with sodium hydroxide.

cerned by the lens system.

Grade: USP, powder, resublimed, pure, reagent,

See optical microscope; electron microscope.

technical, crude.

Hazard: Irritant to skin and eyes. TLV: 10 ppm;

resonance. (1) In chemistry, resonance (or me- STEL 20 ppm; not classifiable as a human carcin-

somerism) is a mathematical concept based on quan- ogen.

1085 RESPONSE ELEMENT

Use: Resorcinol-formaldehyde resins, dyes, pharma-

resorcinol monobenzoate.

ceuticals, cross-linking agent for neoprene, rubber CAS: 136-36-7. C

COOC

OH.

tackifier, adhesives for wood veneers and rubber-to- Properties: White, crystalline solid. Mp 132–135C,

textile composites, manufacture of styphnic acid, bp 140C (0.15 mm Hg). Insoluble in water, benzene,

cosmetics. di-(2-ethylhexyl)phthalate; soluble in acetone and

ethanol. Combustible.

Use: Noncoloring UV inhibitor for various plastics,

resorcinol acetate. (resorcinol monoacetate).

color stabilizer in cosmetic compositions.

CAS: 102-29-4. HOC

OCOCH

Properties: Viscous, pale-yellow or amber liquid;

resorcinolphthalein. See fluorescein.

faint odor; burning taste. Bp 283C (decomposes),

boiling range (10 mm Hg) 150–153C, d

resorcinolphthalein sodium. See uranine.

1.203–1.207. Saturated solution is acid to litmus;

soluble in alcohol and most organic solvents; spar-

␣-resorcylic acid. (3,5-dihydroxybenzoic

ingly soluble in water. Combustible.

acid).

Derivation: Action of acetic anhydride on resor-

CAS: 99-10-5. (OH)

COOH.

cinol.

Properties: White crystals. Mp 237C. Soluble in

Grade: CP, NF.

water, ethanol, and ether. Combustible.

Use: Medicine, cosmetics.

Grade: CP.

Use: Intermediate for dyes, pharmaceuticals, light

resorcinol bis(diphenyl phosphate).

stabilizers, resins.

CAS: 57583-54-7. mf: C

Hazard: Low toxicity by ingestion, inhalation, and

␤-resorcylic acid. (BRA; 2,4-dihydroxyben-

skin contact.

zene carboxylic acid; 2,4-dihydroxybenzoic

acid; 4-hydroxysalicylic acid; 4-carboxyresorci-

nol).

resorcinol dicyanate.

CAS: 89-86-1. (OH)

COOH.

CAS: 1129-88-0. mf: C

Properties: White needles. Mp (decomposes)

Hazard: Low toxicity by ingestion and skin contact.

219–220C, bp decomposes. Almost insoluble in wa-

A mild skin irritant.

ter and benzene; soluble in alcohol, ethyl ether. The

sodium, potassium, ammonium, calcium, and bari-

resorcinol blue. See lacmoid.

um salts are soluble in water; the silver, lead and

copper salts are only slightly soluble. Combustible.

resorcinol diglycidyl ether. (RDGE; 1,3-di-

Use: Dyestuff and pharmaceutical intermediate,

glycidyloxybenzene; m-bis(2,3-epoxypropoxy-

chemical intermediate in synthesis of fine organic

benzene).

chemicals, reagent for iron.

CAS: 101-90-6.

“Resorsabond” [Georgia Pacific]. TM for

lumber resins.

(OCH

❘

)

Available forms: Liquid, powder and slurry.

Properties: Straw-yellow liquid. D 1.21 (25C), bp

Use: For lumber laminating and end jointing applica-

172C (0.8 mm Hg), refr index 1.541 (25C), viscosity

tions.

500 cP (25C), flash p 350F (176C) (COC). Miscible

with most organic resins. Combustible.

respiration. (1) In humans and animals, inhala-

Use: Epoxy resins.

tion of oxygen and exhalation of carbon dioxide; the

oxygen supports the oxidation (combustion) of or-

resorcinol dimethyl ether. (dimethyl resor-

ganic nutrients in the body, yielding energy, carbon

cinol; 1,3-dimethoxy benzene).

dioxide, and water.

CAS: 151-10-0. C

(OCH

)

(2) In growing plants, respiration occurs in both the

Properties: Pale-straw-tint liquid. Bp 204–212C, d

presence and the absence of light. Some of the ener-

1.063–1.066 (25/25C), refr index 1.523–1.527

gy produced in respiration is used to form adenosine

(20C). Combustible.

triphosphate, pyruvic acid, and other metabolic in-

Use: Organic intermediate, flavoring.

termediates. Fruits and vegetables continue to res-

pire after harvest, a fact that must be taken into

account in transportation and storage.

resorcinol-formaldehyde resin. A type of

phenol-formaldehyde resin. Permanently fusible;

respiratory chain. The sequence of electron-

soluble in water, ketones, and alcohols. By dissolv-

carrying proteins that transfer electrons from sub-

ing and adjusting the pH to 7, an adhesive base is

strates to molecular oxygen in aerobic cells.

formed. These adhesives can be used whenever phe-

nolics are used and where fast or room-temperature

cure is desired. An important use of these adhesives

response element. By definition, a response

is in wood gluing, particularly marine plywood. element is a portion of a gene which must be present

1086RESTRICTION

in order for that gene to respond to some hormone or linkage maps. RFLPs usually are caused by muta-

other stimulus. Response elements are binding sites tion at a cutting site.

for transcription factors. Certain transcription fac- See marker; polymorphism.

tors are activated by stimuli such as hormones or

heat shock. A gene may respond to the presence of

restriction map. A “cartoon” depiction of the

that hormone because the gene has in its promoter

locations within a stretch of known DNA where

region a binding site for hormone-activated tran-

restriction enzymes will cut. The map usually indi-

scription factor.

cates the approximate length of the entire piece

(scale on the bottom), as well as the position within

restriction. To “restrict” DNA means to cut it

the piece at which designated enzymes will cut.

with a restriction enzyme.

See: restriction enzyme.

restriction site. See Restriction enzyme.

restriction endonucleases. Site-specific en-

“Reswax” [Borden]. TM for a series of wax-

donucleases causing cleavage of both strands of

resin blends used as coatings and hot-melt adhesives

DNA at points within or near the specific site recog-

in paper conversion. The polymers used include

nized by the enzyme. Many generate sticky ends,

butyl rubber, polyisobutylene, chlorinated rubber,

making them important tools in genetic engineering.

polyethylene, and styrene copolymers.

See restriction enzyme.

ret. To reduce or digest fibers, especially linen, by

restriction enzyme. (restriction endonucle-

enzymatic action.

ases). A class of enzymes generally isolated from

bacteria, which are able to recognize and cut specific

retarder. See inhibitor.

sequences (restriction sites) in DNA. Every copy of

a plasmid is identical in sequence, so if an enzyme

“Reten” 205 [Aqualon]. TM for a strongly

cuts a particular circular plasmid at three sites pro-

cationic, high molecular weight, synthetic, water-

ducing three “restriction fragments”, then a million

soluble polymer. A finely divided white powder,

copies of that plasmid will produce those same re-

dissolves in either hot or cold water to produce clear,

striction fragments a million times over. There are

smooth, viscous, nonthixotropic solutions; available

more than six hundred known restriction enzymes.

in a variety of viscosity grades and cationic func-

Bacteria produce restriction enzymes for protection

tionality. “Reten” 763 is an aqueous solution of a

against invasion by foreign DNA such as phages.

modified polyamide-epichlorohydrin resin.

The bacteria’s own DNA is modified in such a way

Use: Flocculant, binder, and viscosifier.

as to prevent it from being clipped.

retene. (7-isopropyl-1-methylphenanthrene).

restriction-enzyme cutting site. A specific

nucleotide sequence of DNA at which a particular

Properties: Mw 234.36.

restriction enzyme cuts the DNA. Some sites occur

frequently in DNA (e.g., every several hundred base

retention index. (RI). An indication whereby a

pairs); others much less frequently (rare-cutter; e.g.,

compound will appear on a chromatogram with re-

every 10,000 base pairs).

spect to n-paraffins.

restriction enzyme, endonuclease. A pro-

reticulation. Joining of separate lineages on a

tein that recognizes specific, short nucleotide se-

phylogenetic tree, generally through hybridization

quences and cuts DNA at those sites. Bacteria con-

or through lateral gene transfer. Fairly common in

tain over 400 such enzymes that recognize and cut

certain land plant clades; reticulation is thought to be

more than 100 different DNA sequences.

rare among metazoans.

See restriction enzyme cutting site.

reticulopodia. Long thread-like pseudopodia

restriction fragment. (1) The piece of DNA

that branch apart and rejoin, forming a fine network.

released after restriction digestion of plasmids or

They are characteristic of forams.

genomic DNA. See “Restriction enzyme”. One can

digest a plasmid and isolate one particular restriction

retinal. Preferred name for retinene.

fragment (actually a set of identical fragments). (2)

Also describes the fragments detected on a genomic

retinene. (vitamin A aldehyde; retinal).

blot which carry the gene of interest.

O. A necessary component of rhodopsin, the

light-sensitive pigment of the eye. Retinene is the

restriction fragment length polymorphism.

aldehdye form of vitamin A, which is an alcohol.

(RFLP). Variation between individuals in DNA

fragment sizes cut by specific restriction enzymes;

polymorphic sequences that result in RFLPs are

retinol.

used as markers on both physical maps and genetic CAS: 68-26-8. C

OH. (1) A component of vita-

1087 REVERSIBLE ELECTRODE

min A.

retrovirus. An RNA virus containing reverse

See carotene. transcriptase.

(2) A resin distillate similar to rosin oil.

reumycin. See 1-demethyltoxoflavine.

retort. A utensil for distilling volatile materials. A

reverberatory furnace. An ore-roasting kiln

globular glass vessel with an extended side tube

used for distillation. having a curved or sloping roof from which the heat

is deflected onto the material being treated. The fuel

and the charge occupy separate areas in the kiln so

retort gas. The gas that results from the heating

that there is no direct contact between them, thus

of coal in retorts, as in the by-product process of

avoiding contamination of the ore with fuel particu-

coke manufacture.

lates. The heat rising from the ignited fuel impinges

on the curved roof and is reflected downward onto

retorting. (1) A process much used in the early

the ore. After passing over the ore, the heat escapes

years of chemistry for destructive distillation of

through suitably located vents.

heavy organic liquids and for laboratory separa-

tions. It involves the use of a cylindrical vessel made

Reverdin reaction. Migration of iodine during

of glass (for laboratory work), fireclay, or metal,

nitration of iodophenolic ethers.

with a neck bent at a downward angle to facilitate

distillation. For gas manufacture the equipment is

“Reversacol” [James Robinson]. TM for a

built on a heavier scale to handle destructive distilla-

line of photochemical dyes.

tion of coal.

(2) Processing shale oil.

reversal spectrum. A spectrum that can be

(3) Heating canned or pouched foods with steam to

observed in intense, white light. The bright lines in

stop bacterial growth.

the emission spectrum of the gas have traversed a

(4) Volatilization of mercury from gold and silver

luminous gas reversing the color of the dark spec-

amalgams.

trum lines.

See emission spectroscopy.

retro Diels-Alder reaction. Thermal dissoci-

ation of Diels-Alder adducts, occurring most readily

reverse osmosis. See osmosis, desalination.

when one or both fragments are particularly stable.

reverse transcriptase. An RNA-directed

retropinacol rearrangement. Conversion of

DNA polymerase in retroviruses. These viruses are

an alcohol to the rearranged olefin on treatment with

capable of making DNA complementary to an RNA

acid.

and incorporating it into the genome.

4,14-retro-retinol-14-hydroxy-, (14r)-.

reversible. (1) A chemical reaction that proceeds

CAS: 139257-77-5. mf: C

first to the right and then to the left when the ambient

Hazard: A reproductive hazard.

conditions are changed; the product of the first reac-

tion decomposes to the original components as a

trans-retrorsine.

result of different conditions of temperature or pres-

CAS: 15503-87-4. mf: C

sure. Examples are H

O+CO

←→ H

, in which

Hazard: A poison.

the carbonic acid reverts to water and carbon dioxide

Source: Natural product.

on heating; NH

Cl ←→ NH

+ HCl, in which the

ammonium chloride decomposes on heating to am-

retrosynthesis. A computer-assisted analysis of

monia and hydrochloric acid, which recombine on

an organic molecule that is to be synthesized, i.e.,

cooling.

the target molecule, in which the computer works

(2) A colloidal system such as a gel or suspension

back through the precursors of the target substance

that can be changed back to its original liquid form

to a group of possible starting materials that are

by heating, addition of water, or other method. For

readily available from natural sources or as commer-

example, evaporated egg white can be restored (re-

cial products. Retrosynthetic analysis is thus the

constituted) by addition of water.

opposite of the usual direct approach to laboratory

synthesis.

reversible colloid. (lyophilic colloid). A col-

See computational chemistry.

loid that is readily dispersible in a suitable medium

and may be redispersed after coagulation.

retroviral infection. The presence of retroviral

vectors, such as some viruses, which use their re-

reversible electrode. An electrode that owes

combinant DNA to insert their genetic material into its potential to unit charges of a reversible nature, in

the chromosomes of the host’s cells. The virus is contrast to electrodes used in electroplating that are

then propogated by the host cell. destroyed during their use.

1088REVERSION

See chemical reaction; equilibrium constant; irre- by hydrogen gas under press to give the metal, or (2)

versible. passed through an anionic resin from which pure

rhenium can be extracted by a strong mineral acid.

Available forms: Powder that can be consolidated

reversion. The softening and weakening of a

natural rubber vulcanizate when the curing opera- into rods, wires, or strips by powder metallurgy.

tion has been too long continued. Annealed metal is very ductile and can be bent,

coiled, or rolled. Single crystals 2 inches ×

0.05–0.005 inch diameter.

Reynold’s number. The function DUP/␮ used

Hazard: Flammable in powder form.

in fluid flow calculations to estimate whether flow

Use: Additive to tungsten- and molybdenum-based

through a pipe or conduit is streamline or turbulent

alloys, electronic filaments, electrical contact mate-

in nature. D is the inside pipe diameter, U is the

rial, high-temperature thermocouples, igniters for

average velocity of flow, P is density, and ␮ is the

flash bulbs, refractory metal components of mis-

viscosity of the fluid. Different systems of units give

siles, catalyst, plating of metals by electrolysis and

identical values of the Reynold’s number, and val-

vapor-phase deposition.

ues much below 2100 correspond to streamline

flow, while values above 3000 correspond to turbu-

lent flow.

rhenium heptasulfide. Re

Properties: Brown-black solid. D 4.87, decomposes

to ReS

at 600C. Insoluble in water; dissolves in

Rf. Symbol for rutherfordium.

solutions of alkali sulfides.

Hazard: Ignites on heating in air.

RFLP. See restriction fragment length poly-

Use: Catalyst.

morphism.

rhenium heptoxide. Re

RFNA. Abbreviation for red fuming nitric acid.

Properties: Yellow crystals. D 6.103, mp 297C. Dis-

See nitric acid, fuming.

solves in water to form perrhenic acid HReO

; very

soluble in alcohol.

R group. An abbreviation used to denote an

Derivation: Oxidation of metallic rhenium at 400C.

organic substituent such as the R groups of amino

acids.

rhenium pentachloride. ReCl

Properties: Dark-green to black solid. D 4.9, decom-

Rh. Symbol for rhodium.

poses on heating. Decomposes in water; soluble in

hydrochloric acid and alkalies.

rhamnose. C

. A deoxyhexose monosac-

Derivation: By reacting rhenium heptoxide with car-

charide found combined in the form of glycosides in

bon tetrachloride at 400C.

many plants. Two forms exist, ␣- and ␤-, of which

the ␣- is the more stable.

rhenium trichloride. ReCl

Properties: White crystals. Mp 82–92C (␣- form

Properties: Dark red solid, on heating emits green

converts partially to the ␤- form on heating). For

vapor from which the metal may be deposited, non-

equilibrium mixture optical rotation is +9.18 de-

electrolyte in solution, soluble in water and glacial

grees. Very soluble in water and in methanol; solu-

acetic acid.

ble in absolute alcohol.

Derivation: Distillation of rhenium pentachloride.

Use: Synthetic sweetener research.

rhenium trioxychloride. ReO

Cl.

rhenium.

Properties: Colorless liquid. D 3.867 (20/4C), mp

CAS: 7440-15-5. Re. Metallic element, atomic

4C, bp 131C. Decomposes in water; soluble in car-

number 75, group VIIB of the periodic table, aw

bon tetrachloride, reacts readily with organic sub-

186.207; valences

−1, 1 through 7; 4, 6, and 7 are

stances.

most common, the last being the most stable. There

are two isotopes.

rheology. Science of the deformation and flow of

Properties: Silver-white solid or gray to black pow-

materials in terms of stress, strain, and time. Has

der. D 21.02 (20C), mp 3180C, bp 5630C, tensile

important bearing on the behavior of viscous liquids

strength 80,000 psi, high modulus of elasticity, at-

in plastic molding.

tacked by strong oxidizing agents (nitric and sulfuric

See liquid, Newtonian; dilatancy; thixotropy; vis-

acids). Practically insoluble in hydrochloric acid.

cosity.

Retains its crystalline structure all the way to its mp.

Has widest range of valences of any element. Rheni-

rheometer. A device that continuously measures

um-molybdenum alloys are superconductive at

the viscosity and elasticity of resin solutions and

10K. Not attacked by seawater.

polymer melts at high shear rates.

Source: Principally molybdenite.

Derivation: Solutions from refinery residues (mo-

lybdenum ore flue dust, copper ore treatment) are (1)

rhesus factor. (Rh factor). A substance

concentrated by a salting-out processes and reduced present in the red blood cells of the rhesus monkey

1089 RHODIUM CARBONYL CHLORIDE

and of 85% of an average, white, American popula-

rhodinol.

tion. Those whose red cells contain this factor are

CAS: 106-22-9. A mixture of terpene alcohols con-

termed Rh-positive; others, Rh-negative. A negative

sisting principally of l-citronellol.

individual may develop anti-Rh antibodies if Rh-

Properties: Colorless liquid; pronounced roselike

positive red cells enter his blood; such antibodies

odor. D 0.860–0.880 (25C), refr index

can then agglutinate Rh-positive cells. Hemolytic

1.4630–1.4730 (20C), optical rotation −4to−9 de-

reactions may thus occur following transfusion of

grees. Soluble in alcohol and mineral oil; insoluble

Rh-positive blood cells into a recipient previously

in water. Combustible.

sensitized and having Rh antibodies in the serum.

Derivation: From Reunion geranium oil.

Likewise, an Rh-positive fetus, may give rise to

Grade: FCC.

antibodies in the blood of an Rh-negative mother;

Use: Perfumery, flavoring agent.

the antibodies, returning into the fetus may then

produce the disease erythroblastosis fetalis. There

rhodinyl acetate. A mixture of terpene alcohol

are many subtypes of the Rh factor; these can be

acetates consisting primarily of l-citronellyl acetate.

distinguished by serologic tests, and the laws of their

Properties: Colorless to slightly yellow liquid; rose-

inheritance have been determined.

like odor. D 0.895–0.908 (25C), refr index

1.4530–1.4580 (20C), optical rotation −2 to 6 de-

grees. Soluble in alcohol and mineral oil; insoluble

rhizobitoxin. A broad-spectrum herbicide that

in glycerol. Combustible.

attacks young growth and new leaves but has little

Derivation: Action of acetic anhydride on rhodinol

effect on older growth. Said to have low toxicity to

in the presence of sodium acetate.

humans (USDA).

Grade: Technical, FCC.

Use: Perfumery, flavoring agent.

rho acid. See anthraquinone-1,5-disulfonic

acid.

rhodinyl formate. mf: C

Properties: Colorless to slightly yellow liquid; leafy,

rose-like odor. Mw: 184.28, d: 0.901−0.908, refr

rhodamine B. (CI 45170).

index: 1.453−1.458. Soluble in alcohol, fixed oils;

CAS: 81-88-9. C

ClN

. A basic, red fluores-

insoluble in glycerin, propylene glycol, water at

cent dye, structurally related to xanthene.

200C.

Properties: Green crystals or reddish-violet powder.

Use: Flavoring agent.

Very soluble in water and alcohol, forming bluish

red, fluorescent solution; slightly soluble in acids or

alkalies.

rhodium.

Derivation: By fusion of m-diethylaminophenol and

CAS: 7440-16-6. Rh. Metallic element having

phthalic anhydride followed by acidification with

atomic number 45, group VIII of the periodic table,

hydrochloric acid.

aw 102.9055, no isotopes, valence

Use: Red dye for paper, also for wool and silk where

Properties: White solid of platinum group. D 12.41

brilliant fluorescent effects are desired and light-

(20C), mp 1966C, bp 4500C. Insoluble in acids and

fastness is of secondary importance; analytical re-

aqua regia; soluble in fused potassium bisulfate.

agent for certain heavy metals, biological stain.

Harder and higher-melting than platinum or palladi-

um, highest in electrical and thermal conductivity of

the platinum group. High surface reflectivity. A

rhodamine toner. Red to maroon lakes of rho-

strong complexing agent.

damine dyes and phosphotungstic or phosphomo-

Occurrence: Ontario, South Africa, Siberia.

lybdic acid. They have good lightfastness and are

Derivation: Occurs with platinum, from which it is

used principally in printing inks.

recovered during the purification process.

See phosphomolybdic pigment; phosphotungstic

Available forms: Produced as powder that can be

pigment.

fabricated by casting or powder metallurgy tech-

niques. Single crystals are available.

rhodanine. (2-thio-4-keto-thiazolidine).

Hazard: Flammable in powder form. TLV: (insolu-

CAS: 141-84-4.

ble rhodium compounds) 1 mg/m

; (soluble rhodium

salts): 0.01 mg/m

Use: Alloy with platinum for high temperature ther-

❘

C(O)NHC

❘

mocouples, furnace windings, laboratory crucibles,

Properties: Finely crystalline, light yellow color. D

spinnerettes in rayon industry; electrical contacts,

0.868, bulk d 0.617, mp decomposes (often violent-

jewelry, catalyst, optical instrument mirrors, elec-

ly) 166C, pure material 167–168.5C. Soluble in

trodeposited coatings for metals, vacuum-deposited

methanol, ethyl ether, and hot water.

glass coatings, headlight reflectors.

Hazard: May explode when heated to 166C. Toxic

by ingestion.

Use: Organic synthesis (phenylalanine), laboratory

rhodium carbonyl chloride. Rh(CO)

reagent. Properties: Reddish crystals. Mp 125C. Soluble in

1090RHODIUM CHLORIDE

alcohol, benzene, acetone, with decomposition; sol- bis(chlorophenyl)-2,2-dichloroethane and supplied

id material is stable in dry air. as a wettable powder or emulsion concentrate.

Use: Catalyst for organic reactions.

“Rhozyme” [Rohm & Haas]. TM for en-

rhodium chloride. (rhodium trichloride).

zyme concentrate with diastatic or proteolytic activ-

CAS: 10049-07-7. RhCl

ity. Buff-colored powders or liquids of fungal or

Properties: Reddish-brown powder. Mp 450–500C,

bacterial origin that hydrolyze and solublize pro-

bp 800C (sublimes). Insoluble in water and acids;

teins and starches.

soluble in solutions of alkalies and cyanides.

Use: Desizing textile fabrics; drycleaning; liquefac-

Hazard: Toxic by ingestion.

tion of starch paste; fermentation processes; manu-

Use: Manufacture of rhodium trifluoride.

facture of corn syrup, fish solubles, septic tank for-

mulations; animal feed; meat tenderizer.

rhodium (III), triamminetrinitratato-.

See triamminetrinitratatorhodium (III).

rhubarb yellow.

CAS: 478-43-3. mf: C

rhodochrosite. MnCO

with partial replacement

Hazard: Low toxicity by ingestion.

by iron, calcium, magnesium, zinc.

Properties: Light-pink, rose-red, brownish-red, or

RI. See retention index.

brown mineral; white streak; vitreous to pearly lus-

ter; photoluminescent. Found in veins with ores of

Rib. Abbreviation for ribose.

silver, lead, copper manganese. D 3.3–3.6, Mohs

hardness 3–4.

ribavirin. See 1-␤-d-ribofuranosyl-1,2,4-tria-

Occurrence: U.S. (Connecticut, New Jersey, Colo-

zole-3-carboxamide.

rado, Montana, Nevada), Europe.

Use: Manganese ore.

ribbon mixer. A mixing or blending machine

whose essential components are a steel bowl or

rhodonite. An ore of manganese.

trough, jacketed for temperature control, within

See manganous silicate.

which rotates an agitating device consisting of two

or more metal strips (ribbons) pitched in opposite

rhodopsin. The red-light-sensitive pigment of

directions spirally arranged around a central shaft.

the eye (visual purple) consisting of the proteins

The curved and reverse-pitched ribbons operate on

opsin and retinene (vitamin A aldehyde). It occurs in

the principle of the screw; the material is moved

land and marine vertebrates.

forward by one ribbon and backward by another, so

that efficient mixing is effected. Continuous opera-

rhodoxanthin. C

. A natural carotenoid

tion is possible in some types. Such equipment is

pigment used in the food, drug, and cosmetic indus-

used for mixing dry powders, viscous liquids, slur-

tries.

ries, etc., as well as for drying, crystallizing, and

Properties: Soluble in benzene and chloroform;

deaerating. Large sizes have a bowl diameter of 5 ft

slightly soluble in alcohols.

and a length of 9.5 feet.

“Rhonite” [Rohm & Haas]. TM for thermo-

riboflavin. (vitamin B

; 7,8-dimethyl-10-(1

′

-d-

setting modified and unmodified urea-formalde-

ribityl) isoalloxazine).

hyde condensates. Supplied as water-clear solutions

CAS: 83-88-5. C

. A crystalline pigment,

and aqueous pastes. Reactive with cotton, various

the principal growth-promoting factor of the vita-

grades producing shrink resistance, crease proofing,

min B

complex. It functions as a flavoprotein in

or modification of hand.

tissue respiration. A syndrome resembling pellagra

Use: Finishing of natural and synthetic fabrics.

is thought to be due to riboflavin deficiency.

“Rhoplex” [Rohm & Haas]. TM for aque-

ous dispersions of acrylic copolymers. White,

opaque emulsions; various grades differing in

hardness, flexibility, adhesion, and tack of film;

some thermosetting. Produce colorless, transparent

films with outstanding permanence, durability, ad-

hesion, and pigment-binding capacity.

Use: Emulsion paints, paper coatings and saturation,

floor sealers and wax emulsions, textile-backing and

finishing, bonding fibers and pigments, clear and

pigmented coatings on wood and metals.

Properties: Orange-yellow crystals; bitter taste. Mp

282C (decomposes). Slightly soluble in water and

“Rhothane” [Rohm & Haas]. TM for an alcohols; insoluble in lipid solvents; stable to heat in

agricultural insecticide based on 1,1- dry form and in acid solution. Stable to ordinary

COOH

Lys

Glu

Thr

Ala

Ala Ala Lys Phe Glu Glu His Met Asp Ser Ser

Ser Ser

Ser

Ileu

Thr Ser

Ser

Asp

Arg

Glu

Gly

Met

Ser

ArgArg

Ala

Asp

AspAsp

Asp

LeuThr

Thr

Tyr

Thr

ThrThr

Tyr

His

Glu

Ser

Leu

Ala

Asp

Val

Cys

Lys

Asp

Gly

Ser

Glu Glu

Gly

Glu

Thr

Tyr Tyr Tyr

Thr

Met

Lys

LysLys

His

Pro

Phe

Phe Val

Val

Cys

Met

Tyr

Cys

Lys

Ala AlaArg

567891011121314151617181920

33343536373839404142434445464748

115 116117 118119 120 121 122123 124

9094100

VIII

VII

III

75 80

1091 RIBONUCLEIC ACID

oxidation, unstable in alkaline solution and quite Hazard: Mildly toxic by ingestion. An experimental

sensitive to light. In solution, riboflavin has an in-

teratogen.

tense greenish-yellow fluorescence. Amounts are

Use: As an antiviral agent.

expressed in milligram or micrograms of riboflavin.

Source: (Food) Milk, green leafy vegetables, egg

ribonuclease. An enzyme that causes splitting of

yolk, liver, enriched flour, yeast; (commercial) dis-

ribonucleic acid. Pancreatic ribonuclease for exam-

tiller’s residues, fermentation solubles, synthetic

ple, cleaves only phosphodiester bonds that are

production (indirectly from dextrose, lactose, yeast,

linked to pyrimidine-3

′

-phosphates. It is a critical

and whey).

regulator of life processes in the cell. The first en-

Grade: USP, FCC.

zyme to be synthesized (1969), it is composed of 124

Use: Medicine, nutrition, animal feed supplement,

amino acid residues. It is one of the proteins for

enriched flours, dietary supplement.

which the sequence of amino acids has been eluci-

dated (the order or sequence of amino acids is of

riboflavin-5

′

-phosphate. (FMN; flavin mo-

critical importance in the functioning of enzymes,

nonucleotide). The phosphate ester of riboflavin in

genes, and nucleotides).

which the phosphate is esterified to the ribityl por-

See: Genetic code; RNAse.

tion of riboflavin. It functions as a coenzyme for

many flavine enzymes. The riboflavin group has the

ability to take up hydrogen atoms, thus oxidizing the

ribonucleic acid. (ribose nucleic acid; RNA).

substrate.

Generic term for a group of natural polymers con-

Properties: (Sodium salt) Yellow crystals; quite sen-

sisting of long chains of alternating phosphate and

D-

sitive to UV light. Much more soluble than ribofla-

ribose units, with the bases adenine, guanine, cyto-

vin in water.

sine, and uracil bonded to the 1-position of the

Derivation: By treating riboflavin with chlorophos-

ribose. Ribonucleic acid is universally present in

phoric acid.

living cells and has a functional genetic specificity

Use: Dietary supplement, flavor potentiator.

due to the sequence of bases along the polyribonu-

cleotide chain.

riboflavin 5

′

-phosphate sodium.

Four types are recognized:

CAS: 130-40-5. mf: C

127

NaO

P•2H

(1) Messenger RNA, synthesized in the living cell

Properties: Fine orange-yellow crystalline powder;

by the action of an enzyme that carries out the poly-

slt odor. Hygroscopic; sol in water. Decomposed by

merization of ribonucleotides on a DNA template

light when in solution.

region that carries the information for the primary

Use: Food additive.

sequence of amino acids in a structural protein. It is a

ribonucleotide copy of the deoxynucleotide se-

9-␤-D-ribofuranosyladenine. See adenosine.

quences in the primary genetic material.

(2) Ribosomal RNA, that exists as a part of a func-

1-␤-d-ribofuranosyl-1,2,4-triazole-3- tional unit within living cells called the ribosome, a

carboxamide. particle containing protein and ribosomal RNA in

CAS: 36791-04-5. mf: C

. roughly 1:2 parts by weight having a particle weight,

Properties: Mp: 174−176°. Sol in H

O. of about three million. See ribosome.

1092RIBONUCLEOTIDE

Messenger RNA combines with ribosomes to form the balance being proteins. Ribosome crystals have

polysomes containing several ribosome units, usual-

been produced; in the electron microscope these

ly 5 (e.g., during hemoglobin synthesis), complexed

appear as sheets of black dots, each sheet (one ribo-

to the messenger RNA molecule. This aggregate

some thick) containing hundreds of ribosomes in

structure is the active template for protein biosyn-

recurring groups of four.

thesis.

See deoxyribonucleic acid; ribonucleic acid.

(3) Transfer RNA, the smallest and best character-

ized RNA class. Its molecules contain only 80 nu-

D-ribosyl uracil. See uridine.

cleotides per chain. Within the class of transfer RNA

molecules there are probably at least 20 separate

rice bran wax.

kinds, correspondingly related to each of the 20

Properties: Tan to brown hard wax. Mp: 75°. Sol in

amino acids naturally occurring in proteins. Trans-

chloroform, benzene; insol in water.

fer RNA must have at least two kinds of specificity:

Use: Food additive.

(a) It must recognize (or be recognized by) the prop-

er amino acid–activating enzyme so that the proper

rice paper. See straw.

amino acid will be transferred to its free 2

′

-or3

′

-OH

group. (b) It must recognize the proper triplet on the

Richards, Theodore W. (1868–1928). An

messenger RNA–ribosome aggregate. Having these

American chemist born in Germantown, PA. He was

properties, the transfer RNA accepts or forms an

the first American to receive the Nobel Prize in

intermediate transfer RNA–amino acid that finds its

chemistry. He studied chemistry at Haverford and

way to the polysome, complexes at a triplet coding

Harvard, with a doctorate in chemistry from Har-

for the activated amino acid, and allows transfer of

vard where he later became Erving Professor of

the amino acid into peptide linkage.

Chemistry. An outstanding experimental chemist,

(4) Viral RNA, isolated from a number of plant,

his major interests were atomic weights, thermo-

animal, and bacterial viruses, may be considered as a

chemistry, and thermodynamics. He was also a bril-

polycistronic messenger RNA. It has been shown to

liant teacher. He was president of the ACS in 1914,

have molecular weights of one or two million. Gen-

and the recipient of many honorary awards, includ-

erally speaking, there is one molecule of RNA per

ing the Davy, Faraday, and Gibbs medals.

infective virus particle. The RNA of an RNA virus

can be separated from its protein component and is

“Ricilan” [Dow]. TM for esters synthesized

also infective, bringing about the formation of com-

from castor oil and lanolin components. Amber,

plete virus.

viscous liquids.

From article by F. J. Bollum in Encyclopedia of

Use: Hydrophobic emollients, pigment dispersants.

Biochemistry. See deoxyribonucleic acid;

RNA.

ricin.

CAS: 9009-86-3.

ribonucleotide. A nucleotide containing D-ri-

Properties: White powder. The albumin of the castor

bose as its pentose component.

oil bean is the toxic principle. Extracted from the

See nucleotide.

pressed seeds with 10% solution of sodium chloride

followed by precipitation with magnesium sulfate.

riboprobe. A strand of RNA synthesized in-vitro

Hazard: Very highly toxic by ingestion; small parti-

(usually radiolabeled) and used as a probe for hy-

cle in cut, abrasion, eye, or nose may prove fatal.

bridization reactions. An RNA probe can be synthe-

Use: Reagent