795. Arsenic Acid

Nomenclature

CAS number: 7778-39-4
Arsenic acid (AsH3O4); orthoarsenic acid.
AsH3O4; mol wt 141.94.
As 52.78%, H 2.13%, O 45.09%.
H3AsO4.

Description and references

Exists as the hemihydrate. Excessive drying produces As2O5.5/3H2O. Conveniently prepd from As2O3 and HNO3: Simon, Thaler, Z. Anorg. Allg. Chem. 161, 143 (1927); 246, 19 (1941). Toxicity study: Joachimoglu, Biochem. Z. 70, 144 (1915). Review of toxicology and human exposure: Toxicological Profile for Arsenic (PB2000-108021, 2000) 468 pp.

Derivative

Hemihydrate.

Properties

Hygroscopic crystals. Poisonous. Converted to As2O5 by heating above 300°. Freely sol in water, alcohol, glycerol. LD50 i.v. in rabbits: 6 mg/kg (Joachimoglu).

Use

In the manuf of arsenates.