Title: Ammonium Dichromate(VI)
CAS Registry Number: 7789-09-5
Additional Names: Ammonium bichromate
Molecular Formula: Cr2H8N2O7
Molecular Weight: 252.06
Percent Composition: Cr 41.26%, H 3.20%, N 11.11%, O 44.43%
Line Formula: (NH4)2Cr2O7
Literature References: Prepd from ammonium sulfate and sodium dichromate or by the interaction of ammonia gas and chromic acid in soln: Hartford, Ind. Eng. Chem. 41, 1993 (1949); Chromium Chemicals Vol. 52 (Mutual Chem. Div., Allied Chem.) p. 34-39. Review: ACS Monograph Series no. 132, entitled "Chromium," vol. 1, M. J. Udy, Ed. (Reinhold, New York, 1956) passim.
Properties: Bright orange-red crystals. Flammable. Odorless and non-hygroscopic. Crystal system: monoclinic. Crystal habit: prismatic. d425 2.155. Bulk density: 82 lbs/cu ft. Dec at about 180°. Decomposition becomes self-sustaining at about 225° with spectacular swelling and evolution of heat and nitrogen, leaving Cr2O3. Heat of soln -23.0 cal/g. Very sol in water. Soly in water (w/w): 15.16% (0°); 26.67% (20°); 36.99% (40°); 46.14% (60°); 54.20% (80°); 60.89% (100°). Acid reaction. A 1% soln has a pH of 3.95 and a 10% soln has a pH of 3.45.
Density: d425 2.155; Bulk density: 82 lbs/cu ft
CAUTION: Causes skin irritation, ulceration, "chrome sores," perforation of nasal septum, pulmonary irritation.
Use: Source of pure nitrogen (esp in the laboratory); in pyrotechnics (Vesuvius fire); in lithography and photo engraving; in special mordant, catalysts, and porcelain finishes; intermediate in the manufacture of pigments; of magnetic recording materials.