Cyanides of the Metals. 



63 



salt, and to explain similar reactions with platina and other 

 metals, we will endeavour to follow them. 



13. When a saturated solution of cyanide of potassium is 

 added, in small portions, to a cold and strong solution of ni- 

 tromuriate of gold, there is at first a violent effervescence, the 

 solution becomes slightly turbid, and then quite transparent. 

 The reaction may be explained as follows : — 



The first effect is the neutralization of the excess of nitric 

 and muriatic acids contained in the nitro-muriate of gold. 

 This results at the expense of the cyanate of potash and cya- 

 nide of potassium. 



Thus— 2KCy + KO, CyO + 2HC1 + NO5 + 3HO, 

 producing 



2KCI + KONO5 + 2CO2 + NHg + 2CyH, 



or represented thus : 



and forming— 

 3HO 



2HC1 



rsH 



r N 



KO + QyO\ 2C 



L o 



KO 

 NO. — 



2CyH 



2KCI 

 NH. 



2CO0 



KO + NO5 



The solution is now free from acid ; and on a further ad- 

 dition of cyanide of potassium it immediately, by the assistance 

 of water, reacts upon the terchloride of gold. This will be 

 evident from the following formulae, 



2AUCI3 + 8KCy + 8HO, 

 producing 



2(AuCy + KCy) + 6KCl + 2(NH3+C02)+2HCy, 

 or it may be represented thus: — 



'2Au _2(AuCy + KCy) 



6C1> 



2AuCL 



2KCy 



eKCy 



8HO 



2S&3}'^'^^^ + ''"^^ 



HCy 



