292 Experiments on some of the Compounds of Tin with Arsenic. 



Decomposition of AsO^ 2Su02 lOHO. 

 In presence of an excess of a fixed alkali (soda used) this arse- 

 niate of tin is split into two different soda salts, one of which 

 contains all the arsenic, and crystallizes at first in silky needles, 

 while the mother-liquors consist of ordinary stannate of soda : 

 the reaction takes place according to the equation — 



2(As05 2SaO-) +9NaO = 2(As0^6NaO,SnO-) + 3(Sn02 NaO). 



> , ' 



This same salt is also obtained by boiling 2 equivalents of ter- 

 basic arseniate of soda with 1 equivalent of hydrated peroxide 

 of tin. (When hydrate of alumina is taken, an arseniate of alu- 

 mina and soda is obtahied.) To analyse the tin salt, I deter- 

 mined each constituent by direct processes. 



A current of hot air deprived of its carbonic acid passed over 

 100 parts of the salt, gave a loss of 48 per cent, of water. 



100 parts treated with an excess of boiling nitric acid gave 

 13'95 parts of the insoluble arseniate of tin, As0^2SnO-, corre- 

 sponding to — 



7-887 Sn02 = 2 equivs. 

 6063 AsQ5 = 1 equiv. 



]3-95 



100 parts acidulated with hydrochloric acid, treated with a 

 current of sulphuretted hydrogen, gave 41 "5 parts of double 

 sulphuret of tin and arsenic. 



These two weights being ascertained, a mere calculation may 

 be substituted for the tedious operation of M. Levol, for it remains 

 only to calculate the corresponding amount of double sulphurets 

 which 13*95 parts of arseniate of tin would form, to be deducted 

 from the total amount of double sulphuret, 41*5, obtained; as 

 follows : — 



13-95 of AsO^ 2Sn02= 15-825 = AsS5 2SnS2 ; 



and 15-825 AsS^ 2SnS^ deducted from 41*5 double sulphuret, 

 leaves 25-675 of AsS^ = 19-05 AsO■^ 



By evaporating to dryness the hydrochloric acid filtrates, I get 

 37 of chloride of sodium =19*6 soda. 



Recapitulation of the Numbers. 



100-6 100000 470-5 



