Chromium (III) Sulfate, Hydrate
Cr2(SO4)3 - nH2O
CAS No. 10101-53-8
NFPA Rating: Health 1, Flammability 0, Reactivity 0
Physical Properties
Appearance: Violet and green crystals
Odor: Odorless
Solubility: Appreciable in water (24%)
Specific Gravity: 1.8
Boiling Point: Decomposes at red heat
Melting Point: 90C (194F)
Stability and Reactivity
Chromium sulfate is stable under ordinary conditions. When heated, it may decompose to produce chromic oxides (such as chromic acid) and sulfur oxides. It is incompatible (read: don't mix it) with strong oxidizers.
Summary: It's pretty stable. It won't burn, but be prepared for toxic gas if you put it in a fire.
Health Effects and First Aid
Inhalation, ingestion, skin contact, and eye contact all result in irritation of the exposed organs and tissues. Treat by discontinuing exposure and appropriately cleaning any affected body parts: lungs should be given fresh air; skin should be washed with soap and water for at least 15 minutes; eyes should be flushed with water for at least 15 minutes; the stomach should be purged. Get medical attention immediately.
Chromium sulfate is not a carcinogen (trivalent chromium, or chromium (III), is generally far less dangerous than hexavalent chromium, or chromium (VI)). It is not significantly bioaccumulative.
Summary: It's not terribly nasty. Don't eat it. Don't breathe it. Wear proper gloves and goggles, and take basic laboratory safety precautions.
Uses
Chromium sulfate is primarily used in chromium tanning, a common industrial process for turning skins/hides into leather. Leather made with chromium tanning is soft and stretchy, and has a blue-green color (before dyeing). It is also comparatively durable, especially against heat and water.
References:
Mallinckrodt Baker, Inc., formerly J T Baker, Inc. (jtbaker.com)
Cornell University Environmental Health and Safety, material safety data sheets database (msds.ehs.cornell.edu)
Physical and Theoretical Chemistry Laboratory at Oxford University (http://physchem.ox.ac.uk/index.html)