Precipitation of Cuprous Sulphocyanide. 



25 



thoroughly washed, and dried at 105°, were allowed to stand in 

 the solutions to be tested from 40 to 50 hours. After careful 

 filtering through asbestos the copper in the clear filtrate was 

 estimated by the battery or, in cases where the amount was 

 small, by the colorimetric method described above. 







Table 



II. 







Volume of 



liquid, 200 cm3 . 





Cu 2 S 2 (CN) 2 



taken. 



grm. 



HCl 

 sp. grav.. 1 

 cm 3 . 



■18 





NH 4 SCX 

 grm. 



Cu in filtrate, 

 grm. 



0-3 

 0-3 

 0-3 









io- 



0-00035 

 0-00040 

 0050 



0-25 









-(ro) 



0*00018 



03 









™(?o) 



0-00007 



0-3 









•*<*) 



0-00004 



0-3 

 0-3 

 0-3 

 0-3 



2 



2 

 2 



2 



NH 4 C1 



grm. 







2-5 



1-77* 



0-19 



00019 

 0-0013 

 0-0009 

 0-0006 



0-3 

 0-3 



10 

 10 







0-19 



0-0031 

 0-00013 



0-3 



M 



'S) 



t 





0-00045 



0-3 



l 



i / 





0-19 



0-00005 



The solubility is lowest in dilute solutions of ammonium 

 sulphocyanide, and the presence of a small amount of this salt 

 lessens the solubility in hydrochloric acid, and in solutions 

 of ammonium chloride. In decinormal ammonium chloride the 

 solubility is greater than in ammonium sulphocyanide of like 

 strength, but this order is reversed in more concentrated 

 solutions. 



The results of the investigation may be summarized as fol- 

 lows : In the presence of free;}: hydrochloric acid the precipita- 

 tion of cuprous sulphocyanide by a small excess of ammonium 

 sulphocyanide is incomplete, but not injuriously so unless the 



* Equivalent to the amount of hydrochloric acid present, 

 f Approximately. 



\ By free acid is here to he understood that acid which remains in the free state 

 after the interaction with the ammonium bisulphite. 



