with the acid inflame with explosive violence. In contact
with the skin it produces painful wounds. It may be distinguished from
chloric acid by the fact that it does not give chlorine peroxide when
treated with concentrated sulphuric acid, and that it is not reduced
by sulphurous acid. The salts of the acid are known as the
_perchlorates_, and are all soluble in water; the potassium and
rubidium salts, however, are only soluble to a slight extent.
Potassium perchlorate, KClO4, can be obtained by carefully heating the
chlorate until it first melts and then nearly all solidifies again.
The fused mass is then extracted with water to remove potassium
chloride, and warmed with hydrochloric acid to remove unaltered
chlorate, and finally extracted with water again, when a residue of
practically pure perchlorate is obtained. The alkaline perchlorates
are isomorphous with the permanganates.

CHLORITE, a group of green micaceous minerals which are hydrous
silicates of aluminium, magnesium and ferrous iron. The name was given
by A.G. Werner in 1798, from [Greek: chloritis], "a green stone."
Several species and many rather ill-defined varieties have been
described, but they are difficult to recognize. Like the micas, the
chlorites (or "hydromicas") are monoclinic in crystallization and have a
perfect cleavage parallel to the flat face of the scales and plates. The
cleavage is, however, not quite so prominent as in the micas, and the
cleavage flakes though pliable are not elastic. The chlorites usually
occur as salt (H=2-3) scaly aggregates of a dark-green colour. They vary
in specific gravity between 2.6 and 3.0, according to the amount of iron
present. Well-developed crystals are met with only in the species
clinochlore and penninite; those of the former are six-sided plates and
are optically biaxial, whilst those of the latter have the form of acute
rhombohedra and are usually optically uniaxial. The species prochlorite
and corundophilite also occur as more or less distinct six-sided plates.
These four better crystallized species are grouped together by G.
Tschermak as orthochlorites, the finely scaly and indistinctly fibrous
forms being grouped by the same author as leptochlorites.

Chemically, the chlorites are distinguished from the micas by the
presence of a considerable amount of water (about 13%) and by not
containing alkalis; from the soft, scaly, mineral talc they differ in
containing al