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PROPERTIES OF CHROMIC ACID.

CHROMIC ACID.

PART LXXXIX.

Chromic acid exists in combination with various metals andearths. Combined with oxid of lead, it forms the red lead oreof Siberia, called chromate of lead. It has been found united toiron, alumine, and silex, (chromate of iron.) Vauquelin hasproved that it is the colouring matter of the emerald, See. Itprobably exists in other gems.

PROPERTIES OF CHROMIC ACID.

The chromic acid is of a ruby-red colour, and in crystals of aprismatic figure. These are soluble in water, and have a sharp,pungent, and metallic taste. When mixed with filings of tinand muriatic acid, it becomes at first yellowish brown, andafterwards assumes a beautiful green colour. When mixed witha little ardent spirit and nitric acid, it immediately assumes a blu-ish green tinge, which preserves the same shade even after desic-cation. Sulphuric ether gives it the same colour. If paper bedipped in chromic acid, and exposed for some days to the rays ofthe sun, it assumes a green colouf, which does not change in thedark. Muriatic acid, heated in a retort with this acid, pro-duces a strong effervescence, and oxigenated muriatic acid gasis evolved.

Chromic acid, mixed with a solution of the hidro-sulphuret ofpotash, is precipitated in the form of greenish brown flak«s