Strontium Arsenites

An impure strontium orthoarsenite, containing more strontium than corresponds to the formula Sr₃(NaO₃)₂, has been obtained as a white flocculent precipitate by treating strontium chloride solution with potassium orthoarsenite in the cold. If the precipitate is dissolved in a dilute solution of acetic acid, on evaporation strontium hydrogen orthoarsenite, SrHNaO₃.H₂O, is obtained.

Strontium Pyroarsenite, Sr₂As₂O₅.2H₂O, may be prepared by adding an aqueous arsenious acid solution to strontium chloride dissolved in alcohol. The solution is filtered after standing for a time, and the white flocculent precipitate is dried at 100° C. It is easily soluble in water and in acids.

Strontium Metarsenite, Sr(AsO₂)₂.4H₂O, may be obtained by the action of ammonium arsenite on a solution of a strontium salt. The precipitation is increased by the addition of alcohol, since the arsenite is fairly soluble in water. When dried at 100° C. it has the composition Sr(AsO₂)₂.3H₂O. At higher temperatures it decomposes to form strontium oxide, arsenious oxide and a little arsenic. Stavenhagen was unable to obtain the metarsenite in a pure state.