352 



Allen and Crenshaw — Sulphides of Zinc, 



to neutral products, though by a secondary reaction we have 

 usually a very little sulphur dioxide formed. The reaction is 

 the same as with ferrous * salts with excess of thiosulphate, and 

 was worked out in the same way, i.e. weighed quantities of the 

 substances were introduced in solution into glass tubes whicb 

 were exhausted of air, sealed and heated to a certain tempera- 

 ture. On cooling, the precipitate was filtered and washed with 

 water, then with alcohol and dried in the air. Tbe sulphur in 

 it was removed by carbon disulphide. The filtrate was diluted 

 to a definite volume and aliquot parts tested for zinc, free acid 

 and finally unchanged thiosulphate by a standard iodine solu- 

 tion. The following table (Table V) shows the results obtained 

 compared with those calculated for the reaction 4Na 2 S.,0 3 + 

 ZnS0 4 =4Na 2 S0 4 +ZnS+4S. 



Table V. 

 Action of Na 2 S 2 3 on zinc salts. 



No. 



ZnS0 4 .7H 2 

 taken 



Na 2 S 2 3 .5H 2 

 taken 



Water 



Tem- 

 pera- 

 ture 



ZnS + S 



ZnS 



Na 8 S 2 3 .5H 2 

 consumed 



























Found 



Cal. 



Found 



Cal. 



Found 



Cal. 



] 



2-0006 



8-000S 



fgcc 



100° 



1-59 



1-57 



•67 



•68 



6-99 



6-95 



2 



2-000S 



8-000S 



u 



a 



1-56 



u 



•67 



it 



676 



et 



3 



2-000? 



8-000S 



it 



u 



1-51 



" 



•68 



a 



6-35 



it 



4 



2-000S 



8-000 K 



It 



(( 



1-59 



It 



•70 



a 



7-04 



--- 



Some secondary reaction evidently affects the quantity of 

 thiosulphate consumed, but a fuller investigation was not 

 deemed advisable. Small quantities of sulphurous acid are 

 formed, but not enough to cause the variations in 2 and 3. In 

 No. 4, which was heated longer than usual (several days), a 

 little hydrogen sulphide was formed, doubtless according to 

 the equation ]STa 2 S 2 3 + H 2 = ]STa 2 S0 4 + H 2 S, which we have 

 elsewhere established. The excess of thiosulphate would thus 

 be reduced. 



Attempt to form Sphalerite in other ways. 



A number of other methods for the synthesis of sphalerite 

 were tried in which zinc sulphide would be precipitated or 

 crystallized in neutral or alkaline solution. Thus hydrogen 

 sulphide was brought into contact with zinc carbonate and zinc 

 bicarbonate ; and amorphous zinc sulphide was heated with a so- 

 lution of sodium bicarbonate. In every case, no matter how slow 

 the reaction, only amorphous sulphide was obtained. It will, 



* Allen, Crenshaw and Johnston, this Journal, xxxiii, 185, 1912. 



