Arsenous acid
Arsenous acid, also known as arsenious acid or arsenic(III) hydroxide, is a chemical compound. It is also an acid. Its chemical formula is As(OH)3. It has arsenic and hydroxide atoms in it. The arsenic is in its +3 oxidation state.
Properties
Arsenous acid is a colorless solution. It is a weak acid. It reacts with bases to make arsenite salts. It is highly toxic. It cannot be made in a crystalline form because it turns into arsenic trioxide and water again. It is similar to phosphorous acid, although it is not a strong reducing agent.
It is the arsenic analogue of phosphorous acid, but has a different chemical structure: phosphorous acid is normally found in its HPO(OH)
2 tautomer, not P(OH)
3, while HAsO(OH)
2 has not been observed. Organic compounds with the formula RAsO(OH)
2 are known and are called arsonic acids.
Preparation
It is made by dissolving arsenic trioxide or arsenic trichloride in water.
Hydrolysis of arsenic halides (such as arsenic trichloride) makes an chemical equilibrium containing some arsenous acid and hydrohalic acid, and some of the arsenic halide and water.[1]
Arsenous Acid Media
Phosphorous acid exists as the dihydroxy tautomer in contrast to arsenous acid.
Related pages
References
- ↑ Efremov, V. A.. Chemical Equilibria in Hydrolysis of Germanium Tetrachloride and Arsenic Trichloride. Inorganic Materials 38 (8) (2002). p. 847–853. doi:10.1023/a:1019743231095.