R
R. (1) Symbol used to represent an organic group Source: Natural product.
in a chemical formula, for example CH
3
,C
2
H
5
,C
6
H
5
,
etc. (2) A free radical (, R Code: ). (3) The gas
racephedrine. (racemic ephedrine; dl-ephed-
constant, equal to p
0
v
0
/273C. (4) Abbreviation of
rine). C
10
H
15
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 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
43
H
82
N
16
O
12
.
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
4
+
,
using -radiation from cobalt-60. (2) Cross-linking
SO
4
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
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
2
.
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
3
.
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
2
.
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
4
.
“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
18
H
32
O
16
5H
2
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
13
H
22
N
4
O
3
SC
6
H
5
BiO
7
.
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
12
,
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
2
O
3
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
4
OCN
either parent. In higher organisms, this can occur by
(NH
2
)
2
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
8
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
4
+
paraffins and cycloparaffins by sulfur dioxide and
H
2
O 3H
2
+ 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
Al
2
O
3
), 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
4
[Cr(NH
3
)
2
(SCN)
4
]H
2
O.
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
35
H
42
N
2
O
9
. 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
37
H
40
O
9
.
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
6
H
4
(OH)
2
.
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
6
H
5
COOC
6
H
4
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
6
H
4
OCOCH
3
.
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)
2
C
6
H
3
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
30
H
24
O
8
P
2
.
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)
2
C
6
H
3
COOH.
CAS: 1129-88-0. mf: C
8
H
4
N
2
O
2
.
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.
C
6
H
4
(OCH
2
C
HO
CH
2
)
2
.
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
6
H
4
(OCH
3
)
2
.
(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
C
18
H
18
.
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.
C
20
H
28
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
20
H
29
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
20
H
30
O
2
.
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
18
H
25
NO
6
.
sure. Examples are H
2
O+CO
2
←→ H
2
CO
3
, in which
Hazard: A poison.
the carbonic acid reverts to water and carbon dioxide
Source: Natural product.
on heating; NH
4
Cl ←→ NH
3
+ 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
2
S
7
.
Properties: Brown-black solid. D 4.87, decomposes
to ReS
2
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
2
O
7
.
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
4
; 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
5
.
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
6
H
12
O
5
. 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
3
.
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
3
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 4to9 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
11
H
20
O
2
Properties: Colorless to slightly yellow liquid; leafy,
rose-like odor. Mw: 184.28, d: 0.9010.908, refr
rhodamine B. (CI 45170).
index: 1.4531.458. Soluble in alcohol, fixed oils;
CAS: 81-88-9. C
28
H
31
ClN
2
O
3
. 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
=
3.
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
3
; (soluble rhodium
salts): 0.01 mg/m
3
.
Use: Alloy with platinum for high temperature ther-
S
CH
2
C(O)NHC
S.
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)
2
Cl
2
.
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
3
.
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
15
H
8
O
6
.
rhodochrosite. MnCO
3
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
40
H
50
O
2
. 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
2
; 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
17
H
20
N
4
O
6
. 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
2
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
NH
2
NH
2
NH
2
NH
2
NH
2
NH
2
NH
2
NH
2
NH
2
NH
2
NH
2
NH
2
NH
2
NH
2
COOH
NH
2
NH
2
NH
2
NH
2
Lys
Glu
Thr
Ala
Ala Ala Lys Phe Glu Glu His Met Asp Ser Ser
Ser Ser
Ser
Ileu
Ileu
Ileu
Thr Ser
Ser
Ser
Ser
Asp
Asp
Asp
Arg
Glu
Glu
Gly
Met
Ser
Ser
Ser
Ser
ArgArg
Ala
Ala
Asp
AspAsp
Asp
Asp
LeuThr
Thr
Tyr
Thr
ThrThr
Tyr
Tyr
His
Glu
Glu
Glu
Ser
Leu
Ala
Ala
Ala
Ala
Ala
Asp
Asp
Asp
Val
Val
Val
Val
Val
Val
Cys
Cys
Cys
Cys
Lys
Lys
Asp
Asp
Asp
Gly
Ser
Glu Glu
Gly
Glu
Glu
Thr
Tyr Tyr Tyr
Thr
Met
Lys
Lys
LysLys
His
His
Pro
Pro
Pro
Pro
Phe
Phe Val
Val
Val
Cys
Cys
Met
Tyr
Cys
Cys
Lys
Lys
Ala AlaArg
1
2
3
4
567891011121314151617181920
21
22
23
24
25
26
27
28
29
30
31
32
33343536373839404142434445464748
49
50
51
52
53
54
55
60
115 116117 118119 120 121 122123 124
9094100
VIII
VII
VI
II
III
IV
V
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
H
20
N
4
NaO
9
P2H
2
O.
(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
8
H
12
N
4
O
5
. roughly 1:2 parts by weight having a particle weight,
Properties: Mp: 174176°. Sol in H
2
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