Preparation of sodium thioarsenate octahydrate
24.5 g of arsenic trisulfide are dissolved in 100ml of an aqueous solution containing 72g of sodium sulfide 9-hydrate; 6.4g of sulfur in finely powdered form are added and the mixture gently refluxed until all the sulfur has dissolved. The solution is not evaporated to dryness, neither is the salt subjected to recrystallization, because of accompanying decomposition. The yield, which depends on the extent of evaporation, is usually about 60g.
Inorganic laboratory preparations, by G. G. Schlessinger, 69, 1962