90 AKSENIC, ANTIMONY, AND TIN. 



the arsenic as arsenious acid, it is precipitated by hy- 

 drosulphuric acid as in No. 52. 



62. ARSENIC, ANTIMONY, AND TIN. 



The compound is divided as finely as possible, and 

 carefully oxidized with strong and pure nitric acid, 

 the mass evaporated to dryness and fused in a silver 

 crucible with eight times its weight of hydrate of soda, 

 the evaporating vessel being previously rinsed with 

 solution of soda, which is added to the contents of the 

 crucible and evaporated to dryness. The fused mass 

 is treated with hot water, then diluted with water, and 

 one-third its volume of strong alcohol added. The 

 mass is allowed to stand for twenty-four hours and 

 frequently stirred ; the antimoniate of soda is then fil- 

 tered off, and washed first with a mixture of 2 vols. of 

 water and 1 vol. of alcohol, next with a mixture of 

 equal vols., and lastly with a mixture of 3 vols. of 

 alcohol and 1 vol. of water, adding to each a few drops 

 of solution of carbonate of soda. The washed salt is 

 treated as in No. 60. 



The alkaline filtrate is supersaturated with hydro- 

 chloric acid, which produces a bulky precipitate of 

 arseniate of binoxide of tin. Without filtering this off, 

 the liquor is saturated with sulphuretted hydrogen, 

 the precipitate thus converted into a dark brown mix- 

 ture of bisulphide of tin and tersulphide of arsenic, 

 and the liquor then allowed to stand for twenty-four 

 hours in the closed vessel. The precipitate is now 

 collected on a weighed filter and dried at 100. The 

 separation of the tin and arsenic is effected by heating 

 in sulphuretted hydrogen, as in No. 53, 



A weighed portion of the entire precipitate might 

 also be jnixed with about 12 times its weight of a 



