tion of chloric(I) acid in hot solutions.
It is both a strong acid and a power-
ful oxidizing agent; hot solutions of
the acid or its salts have been known
to detonate in contact with readily
oxidized organic material.
chloric(VII) acid (perchloric acid)
An unstable liquid acid, HClO 4 ; r.d.
1.76; m.p. –112°C; b.p. 39°C (50
mmHg); explodes at about 90°C at at-
mospheric pressure. There is also a
monohydrate (r.d. 1.88 (solid), 1.77
(liquid); m.p. 48°C; explodes at about
110 °C) and a dihydrate (r.d. 1.65; m.p.
–17.8°C; b.p. 200°C). Commercial
chloric(VII) acid is a water azeotrope,
which is 72.5% HClO 4 , boiling at
203 °C. The anhydrous acid may be
prepared by vacuum distillation of
the concentrated acid in the presence
of magnesium perchlorate as a dehy-
drating agent. Chloric(VII) acid is
both a strong acid and a strong oxi-
dizing agent. It is widely used to de-
compose organic materials prior to
analysis, e.g. samples of animal or
vegetable matter requiring heavy-
metal analysis.
chlorideSee halide.
chlorination1.A chemical reac-
tion in which a chlorine atom is in-
troduced into a compound. See
halogenation. 2.The treatment of
water with chlorine to disinfect it.
chlorineSymbol Cl. A halogen el-
ement; a.n. 17; r.a.m. 35.453; d. 3.214
gdm–3; m.p. –100.98°C; b.p. –34.6°C.
It is a poisonous greenish-yellow
gas and occurs widely in nature as
sodium chloride in seawater and as
halite (NaCl), carnallite (KCl.MgCl 2.
6H 2 O), and sylvite (KCl). It is manu-
factured by the electrolysis of brine
and also obtained in the Downs
process for making sodium. It has
many applications, including the
chlorination of drinking water,
bleaching, and the manufacture of a
large number of organic chemicals.
It reacts directly with many el-
ements and compounds and is a
strong oxidizing agent. Chlorine
compounds contain the element in
the 1, 3, 5, and 7 oxidation states. It
was discovered by Karl Scheele in
1774 and Humphry Davy conÜrmed
it as an element in 1810.
A- Information from the WebElements site
chlorine dioxideA yellowish-red
explosive gas, ClO 2 ; d. 3.09 g dm–3;
m.p. –59.5°C; b.p. 9.9°C. It is soluble
in cold water but decomposed by hot
water to give chloric(VII) acid, chlo-
rine, and oxygen. Because of its high
reactivity, chlorine dioxide is best
prepared by the reaction of sodium
chlorate and moist oxalic acid at
90 °–100°C, as the product is then di-
luted by liberated carbon dioxide.
Commercially the gas is produced by
the reaction of sulphuric acid con-
taining chloride ions with sulphur
dioxide. Chlorine dioxide is widely
used as a bleach inÛour milling and
in wood pulping and alsoÜnds appli-
cation in water puriÜcation.chlorine monoxideSee dichlo-
rine oxide.chlorite1.See chlorates. 2.A
group of layered silicate minerals,
usually green or white in colour, that
are similar to the micas in structure
and crystallize in the monoclinic
system. Chlorites are composed of
complex silicates of aluminium,
magnesium, and iron in combina-
tion with water, with the formula
(Mg,Al,Fe) 12 (Si,Al) 8 O 20 (OH) 16. They are
most common in low-grade meta-
morphic rocks and also occur as sec-
ondary minerals in igneous rocks as
alteration products of pyroxenes, am-
phiboles, and micas. The term is de-121 chlorite
c