1335 X-RADIATION
Derivation: Reduction of xanthone with alcohol and Complex compounds containing nitrogen bonded to
sodium. xenon have also been prepared.
Grade: CP (analytical). Hazard: Toxic by inhalation; oxidizing agents,
Use: Determination of urea and DDT. strong irritant.
xatral. xenyl. The biphenyl group C
6
H
5
C
6
H
4
−.
CAS: 81403-68-1. mf: C
19
H
27
N
5
O
4
•ClH.
Hazard: A poison.
p-xenylamine. See p-aminodiphenyl.
X chromosome. One of the two sex chromo- xerography. A “dry” method of photography or
somes, X and Y. photocopying. A metal plate is covered with a layer
See Y chromosome; sex chromosome. of photoconductive powder, such as selenium; the
surface of this plate is given an electric charge by
passing it under a series of charged wires. An image
Xe. Symbol for xenon.
of the material to be photographed is projected onto
the charged plate through a camera lens. The electric
xenograft. Tissue or organs from an individual of
charges disappear in the areas exposed to light, but
one species transplanted into or grafted onto an
elsewhere the surface retains its charge. A powder
organism of another species, genus, or family. A
consisting of a coarse carrier and a fine developing
common example is the use of pig heart valves in
resin is then spread over the plate. Adhesion be-
humans.
tween powder and plate occurs only at the charged
areas. Elsewhere developing resin and carrier are
3-(2-xenolyl)-1,2-epoxypropane.
not retained on the plate, which thus has become a
Use: Food additive; plasticizer.
negative of the original image. A positive is ob-
tained by placing a piece of paper against the plate
xenon. Xe. Element of atomic number 54, noble
and applying an electric charge as in the first stage of
gas group of the periodic table, aw 131.30, valences
the process. This causes adhesion of developing
=
2, 4, 6, 8; nine stable isotopes.
resin and its carrier to the paper. This positive print is
Properties: Colorless, odorless gas or liquid. Gas (at
fixed by heating in a press for a few seconds to melt
STP) has d 5.8971 g/L (air
=
1.29 g/L), dielectric
the developing resin and fuse it to the paper. Colored
constant 1.0012 (25C) (1 atm); liquid has bp
prints are possible by use of suitable developing
−108.12C (1 mm Hg), d (at bp) of 1.987 g/cc; lique-
resins. Various materials other than paper can thus
faction temp −106.9C. Chemically unreactive but
be printed.
not completely inert. Noncombustible.
Derivation: Fractional distillation of liquid air.
xibornol. (6-isobornyl-3,4-xylenol). C
18
H
26
O.
Use: Luminescent tubes, flash lamps in photography,
Properties: Crystalline solid or viscous, yellowish
fluorimetry, lasers, tracer studies, anesthesia.
liquid. D 1.02, refr index 1.538.
See noble gas; xenon compounds.
Use: Antibacterial agent, rubber antioxidant.
xenon compounds. Xenon tetrafluoride, XeF
4
,
X-linked. Shortened form for cross-linked, e.g.,
is easily prepared by mixing fluorine and xenon in
X-linked polyethylene.
gaseous form, heating in a nickel vessel to 400C, and
cooling. The product forms large, colorless crystals.
XLPE. Trade abbreviation for cross-linked poly-
The difluoride and hexafluoride, XeF
2
and XeF
6
,
ethylene.
also colorless crystals, can be obtained somewhat
similarly. The hexafluoride melts to a yellow liquid
XPS. Abbreviation for X-ray photoelectron spec-
at 50C and boils at 75C. Many xenon fluorine com-
troscopy.
plexes with other compounds are also known. Xe-
non oxytetrafluoride, XeOF
4
, a volatile liquid at
room temperature, is obtained from the reaction of
x-radiation. (Roentgen rays; x rays). Electro-
xenon hexafluoride and silica. Gram amounts have magnetic radiation of extremely short wavelength
been isolated and studied. (0.06–120 A
˚
), emitted as the result of electron tran-
All these fluorides must be protected from moisture sitions in the inner orbits of heavy atoms bombarded
to avoid formation of xenon trioxide, XeO
3
, a color- by cathode rays in a vacuum tube. Those of the
less, nonvolatile solid that is dangerously explosive shortest wavelength have the highest intensity and
when dry. Its solution, the so-called xenic acid, is a are called “hard” X rays. X-radiation was discov-
stable weak acid but a strong oxidizing agent, which ered by Roentgen in 1898. Its properties are (1)
will even liberate chlorine from hydrochloric acid. penetration of solids of moderate density, such as
In an alkaline solution, xenon trioxide reacts to give human tissue but retardation by bone, barium sul-
free xenon and perxenate, such as Na
4
XeO
6
•8H
2
O. fate, lead, and other dense materials. (2) Action on
Perxenates are probably the most powerful oxidiz- photographic plates and fluorescent screens. (3) Ion-
ing agents known, just as the xenon fluorides are ization of the gases through which they pass. (4)
extremely effective fluorinating agents. Ability to damage or destroy diseased tissue; there is