Sodium pyroarsenate

Other salts described are disodium hydrogen orthoarsenate,9 NagHAs04, converted by heat into sodium pyroarsenate,10 Na4As207 and sodium dihydrogen orthoarsenate,11 NaHgAsO ... 

SYNS DIARSENIC ACID, TETRASODIUM SALT SODIUM ARSENATE (DOT) SODIUM DIARSENATE SODIUM PYROARSENATE TETRASODIUM... 

Aluminium Pyroarsenate, Al4(As207)3, is obtained7 by fusing at as low a temperature as possible a mixture of alumina and 15 to 16 times its weight of sodium or potassium dihydrogen arsenate colourless transparent crystals are formed on cooling. These dissolve only very sparingly in hot water, but are readily soluble in dilute acids. 

Chromium Pyroarsenate, Cr4(As207)3, is produced when a small quantity of chromium sesquioxide is fused at a low temperature with sodium or potassium dihydrogen arsenate.12 It yields green transparent... 

The salt may also be obtained by the action of hot water on strontium dihydrogen orthoarsenate 8 or on the pyroarsenate 9 or by the action of ammonia on a hot solution in hydrochloric acid of the precipitate obtained by mixing solutions of strontium chloride and sodium monohydrogen orthoarsenate.10 In the last case the anhydrous salt crystallises out, but if the mother liquor is kept in an atmosphere of ammonia, the monohydrate, SrHAs04.H20, crystallises out. The density of the latter is 3-606 at 15° C. and of the anhydrous salt 4-035. The monohydrate becomes anhydrous at 130° C. and at a higher temperature yields the pyroarsenate.11... 

A basic stannic pyroarsenate, SnAs2O7.SnO3.10H2O, is obtained when the white gelatinous precipitate formed by boiling a solution containing sodium stannate, excess of sodium orthoarsenate and nitric acid, is dried at the ordinary temperature.4 The salt becomes anhydrous at 120Q C. 

Zireonyl Pyroarsenate, (Zr0)2As207.nH20, is obtained as a white precipitate when sodium monohydrogen orthoarsenate is added to a solution of zirconium sulphate.7 When dried at 110° C. the monohydrate, (Zr0)2As207.H20, remains. It is insoluble in water, but readily dissolves in hydrochloric acid. 

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