X
xanthates Salts or esters containing the group –SCS(OR), where R is
an organic group. Cellulose xanthate
is an intermediate in the manufacture of *rayon by the viscose process.
xanthene A heterocyclic compound having three fused rings with
one oxygen atom, C 13 H 10 O; m.p.
101–102°C b.p. 310–312°C. The ring
structure is present in a class of xanthene dyes.
xanthine A purine base, C 5 H 4 N 4 O 2 ,
found in many organisms. See
methylxanthines.
xanthone (dibenzo-4-pyrone) A
colourless crystalline compound,
C 13 H 8 O 2 ; m.p. 174°C. The ring system
is present in xanthone dyes.
xenobiotic Any substance foreign
to living systems. Xenobiotics include
drugs, pesticides, and carcinogens.
DetoxiÜcation of such substances occurs mainly in the liver.
xenon Symbol Xe. A colourless
odourless gas belonging to group 18
of the periodic table (see noble
gases); a.n. 54; r.a.m. 131.30; d. 5.887
g dm
–3
; m.p. –111.9°C; b.p. –107.1°C.
It is present in the atmosphere
(0.00087%) from which it is extracted
by distillation of liquid air. There are
nine natural isotopes with mass
numbers 124, 126, 128–132, 134, and
136. Seven radioactive isotopes are
also known. The element is used in
Ûuorescent lamps and bubble chambers. Liquid xenon in a supercritical
state at high temperatures is used as
a solvent for infrared spectroscopy
and for chemical reactions. The compound Xe
+
PtF 6
– was the Ürst noblegas compound to be synthesized.
Several other compounds of xenon
are known, including XeF 2 , XeF 4 ,
XeSiF 6 , XeO 2 F 2 , and XeO 3 . Recently,
compounds have been isolated that
contain xenon–carbon bonds, such as
[C 6 H 5 Xe][B(C 6 H 5 ) 3 F] (pentaÛuorophenylxenon Ûuoroborate), which is
stable under normal conditions. The
element was discovered in 1898 by
Ramsey and Travers.
A
• Information from the WebElements site
XPS X-ray photoelectron spectroscopy. See photoelectron spectroscopy.
O
O
Xanthone
N
H
N
H
N
N
H
O
O
Xanthine
O
Xanthene
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xanthates Salts or esters containing the group –SCS(OR), where R is
an organic group. Cellulose xanthate
is an intermediate in the manufacture of *rayon by the viscose process.
xanthene A heterocyclic compound having three fused rings with
one oxygen atom, C 13 H 10 O; m.p.
101–102°C b.p. 310–312°C. The ring
structure is present in a class of xanthene dyes.
xanthine A purine base, C 5 H 4 N 4 O 2 ,
found in many organisms. See
methylxanthines.
xanthone (dibenzo-4-pyrone) A
colourless crystalline compound,
C 13 H 8 O 2 ; m.p. 174°C. The ring system
is present in xanthone dyes.
xenobiotic Any substance foreign
to living systems. Xenobiotics include
drugs, pesticides, and carcinogens.
DetoxiÜcation of such substances occurs mainly in the liver.
xenon Symbol Xe. A colourless
odourless gas belonging to group 18
of the periodic table (see noble
gases); a.n. 54; r.a.m. 131.30; d. 5.887
g dm
–3
; m.p. –111.9°C; b.p. –107.1°C.
It is present in the atmosphere
(0.00087%) from which it is extracted
by distillation of liquid air. There are
nine natural isotopes with mass
numbers 124, 126, 128–132, 134, and
136. Seven radioactive isotopes are
also known. The element is used in
Ûuorescent lamps and bubble chambers. Liquid xenon in a supercritical
state at high temperatures is used as
a solvent for infrared spectroscopy
and for chemical reactions. The compound Xe
+
PtF 6
– was the Ürst noblegas compound to be synthesized.
Several other compounds of xenon
are known, including XeF 2 , XeF 4 ,
XeSiF 6 , XeO 2 F 2 , and XeO 3 . Recently,
compounds have been isolated that
contain xenon–carbon bonds, such as
[C 6 H 5 Xe][B(C 6 H 5 ) 3 F] (pentaÛuorophenylxenon Ûuoroborate), which is
stable under normal conditions. The
element was discovered in 1898 by
Ramsey and Travers.
A
• Information from the WebElements site
XPS X-ray photoelectron spectroscopy. See photoelectron spectroscopy.
O
O
Xanthone
N
H
N
H
N
N
H
O
O
Xanthine
O
Xanthene
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