This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
The liquor sodoe arseniatis contains 4 gr. of the anhydrous salt in 1 oz. of distilled water.
The salt occurs in colorless transparent prisms soluble in water and alkaline in reaction: the solution is also colorless and alkaline.
Arsenic Acid, As2O5, the higher oxide of arsenic, is also white and solid, but is so soluble as to be almost deliquescent, and it has a strong acid reaction. It is not employed in medicine in its free state, but in combination with soda and iron. In the arts it is largely used in the printing of cotton stuffs, and in the manufacture of aniline dyes.
Ferri Arsenias - Arseniate of Iron, Fe3As2O8 (v. p. 134).