66 Messrs. Glassford and Napier on the 



20 grs. yielded 1332 gold = C6'60 per cent. 

 20grs. ... 13-25 ... =66-25 



A sample of the former salt was carefully recrystallized, 

 and placed for some time under a receiver over oil of vitriol ; 

 it gave the foUovi'ing result : — 



20 grs. yielded 13-35 of gold = 66-75 per cent. 



The mean of these results is 66'54< 



10 grs. of the salt were treated with nitric acid, and, the 

 acid being completely expelled by evaporation, they were 

 carefully collected and dried, yielded 8-85 grs. of cyanide of 

 gold = 88-50 per cent. 



The calculated amount of gold and of cyanide of gold con- 

 tained in a salt consisting of single equivalents of cyanide of 

 gold, cyanide of potassium and water, is of gold 66-37, and of 

 cyanide of gold 88-30. 



Our results approximate so closely to the calculated result, 

 that we consider ourselves warranted in giving the formula 

 AuCy + KCy + HO. 



17. In conclusion we may add, that from these results we 

 have no hesitation in saying, that the salt described by Meillet 

 as prepared by saturating chloride of gold with cyanide of 

 potassium is not the auro-cyanide of potassium, but the cyan- 

 ide of gold and potassium as described above. 



IX. Oti the Cyanides of the Metals, and their Combinations 

 nsoith Cyanide of Potassium. Part II. Cyanide of Silver. 

 By Messrs. Charles F. O. Glassford a;z^ James Napier*. 

 T^HE compound that is formed by the union of cyanogen 

 ■'- with silver has been long known, and its composition as- 

 certained to be 1 equivalent of silver with 1 ecjuivalent of 

 cyanogen. The method of preparing this salt, as given in 

 most chemical works, is by adding hydrocyanic acid to the 

 nitrate or any other soluble salt of silver, when the cyanide 

 of silver falls as a white precipitate. This method we have 

 found, on the large scale, to be both disagreeable and tedious, 

 and have therefore adopted the following method for its pre- 

 paration. To a neutral solution of nitrate of silver is added 

 cyanide of potassium so long as a precipitate is formed. No 

 hydrocyanic acid is given offj the precipitate being washed 

 from the nitrate of potash may be used for any purpose re- 

 quired. If the cyanide of potassium, however, contains any 

 cyanate or carbonate, they form impurities in the precipitated 

 cyanide of silver; these can be separated by digesting the 



* Communicated by the Chemical Society; having been read March 4, 

 1844. 



