260 REPORT—1896. 
Classen has taken advantage of the fact that tin is not deposited from 
a concentrated solution of the sodium sulpho-salt upon electrolysis in 
order to separate it from antimony. The mixed sulphides are dissolved 
in sodium sulphide, 1-2 grme. of sodium hydrate added, and the 
solution electrolysed, either cold with a current of 0:2 ampere, or warm 
with a current of about 1:0 ampere. Any polysulphides present must be 
oxidised with hydrogen peroxide. The deposited antimony is washed and 
dried as usual. The residual solution contains the tin, which is deter- 
mined either by boiling with ammonium sulphate and electrolysing the 
solution of the ammonium sulpho-salt thus formed, or by converting the 
sulphide of tin into stannic oxide, and this into the double ammonium 
oxalate for electrolysis. 
Behaviour of Tin in the Electrolysis of its Sodium Sulpho-salt. 
A few experiments were first tried to ascertain under what conditions 
tin is not deposited from its sodium sulpho-salt. The tin was first precipi- 
tated as sulphide, the precipitate thoroughly washed, and then dissolved 
in sodium sulphide solution of sp. gr. 1:18. The solution was diluted to: 
175 c.c., electrolysed with a current C.D.,9) of 0°2 ampere and 3:2 volts 
Tin taken: Grme. Tin found: Grme. Sodtinm Sol ae ae 
added 
071026 0:0280 10 c.c. 
0:1026 No deposit 30 c.c. 
0:1026 + 50) Ge; 
The above quite confirm Classen’s statement that tin is only incom- 
pletely deposited from a dilute solution of its sodium sulpho-salt, and not ‘ 
at all from concentrated solutions. Provided the presence of antimony 
has noveffect on the behaviour of the tin, the addition of 30 c.c. of sodium 
sulphide solution under the above conditions is sufficient to prevent the 
separation of the latter. 
The Separation of Antimony from Tin in Sodium Sulphide Solution. 
The following method was adopted in the separation. The mixture of 
antimony and tin solutions (each prepared as described above) were 
precipitated with sulphuretted hydrogen, and the precipitated sulphides 
collected and thoroughly washed. They were then dissolved in 50 c.c. of 
sodium sulphide solution (sp. gr. 1°18), filtered, 1 grme. sodium hydrate 
added, diluted to 175 c.c., and electrolysed overnight. The tin in the 
residual solution can be converted into the ammonium sulpho-salt by heat- 
ing it with 25 grme. of pure recrystallised ammonium sulphate, the solu- 
tion being boiled for ten minutes after the evolution of the sulphuretted 
hydrogen has ceased, and the resulting solution electrolysed, as de- 
scribed under the determination of tin (Series V.). This method of 
procedure is, however, unnecessarily lengthy, and electrolysis presents no 
advantages after the separation of the antimony. It is much simpler to 
precipitate the tin from the solution of its sodium sulpho-salt by the 
addition of acid, and to convert the sulphide direct into the oxide by the 
usual gravimetric method, and weigh this. This method was adopted in 
most cases. ‘The conversion into the ammonium sulpho-salt is, however, 
quite reliable, and equally accurate results were obtained by both methods. 
