Chemical Properties
Green, gelatinous precipitate. Decomposes to chromic oxide by heat. Insoluble in water;
soluble in acids and strong alkalies.
Physical properties
Bluish-green powder or green gelatinous precipitate; decomposes to chromium(III) oxide on heating; insoluble in water; soluble in dilute mineral acids when freshly prepared, becoming insoluble on aging; soluble in strong alkalis.
Uses
Guignet’s green, catalyst, tanning agent, mordant.
Preparation
Chromium(III) hydroxide may be prepared by precipitation from mixing ammonium hydroxide solution with a soluble chromium(III) salt, such as chromium(III) chloride or nitrate:
CrCl
3 + 3NH
4OH → Cr(OH)
3 + 3NH
4Cl.
Safety Profile
A confirmed
carcinogen. A poison. A powerful oxidizer.
A powerful irritant of skin, eyes, and
mucous membranes.
Toxics Screening Level
The initial threshold screening level (ITSL) for chromium III hydroxide is 0.5 micrograms per cubic meter (μg/m3) based on a 24-hour averaging time.
