64- Messrs. Glassford and Napier on the 



When, however, the solution of nitro-muriate of gold is re- 

 cently prepared, saturated and hot, a portion of the ammonia 

 formed reacts upon a portion of the gold, forming aurate of 

 ammonia, which precipitates along with the cyanide of gold ; 

 on the addition of cyanide of potassium the ammonia is libe- 

 rated and the double salt of gold and potassium is produced. 



14". The following process which we have employed is 

 beautifully calculated for obtaining a large quantity of salt in 

 a very few hours, and at comparatively little trouble. 



A solution of cyanide of potassium is prepared, which con- 

 tains about six times as much cyanide as the quantity of gold 

 wished to be dissolved. The cyanide may be dissolved in 

 twice, thrice or four times its weight of distilled water and care- 

 fully filtered to separate any insoluble matters with which the 

 cyanide is usually contaminated ; this solution is then to be 

 gently and carefully raised to a temperature of 100"^ F. in an 

 earthenware or glass vessel. Two plates of gold are placed 

 in the solution at the opposite sides of the vessel, and these 

 connected by means of copper wires to the poles of a small 

 galvanic battery, composed of two or three pairs of zinc 

 and copper plates, and excited with dilute acid. As soon as 

 the circuit is completed the operation commences, gold is dis- 

 solved from that plate connected with the copper end of the 

 battery, passes into the solution, and is only partly deposited 

 upon the opposite plate, whilst a gentle flow of gas is evolved 

 from the negative pole. The solution of cyanide of potassium 

 rapidly consumes the gold which is dissolved at the positive 

 pole and becomes a double salt of cyanide of gold and potas- 

 sium. The gold which deposits upon the negative pole is in 

 minute grains, occasionally quite brown, and is beautifully 

 crj^stalline. The operation is much facilitated by having the 

 positive pole or plate of gold several times larger than the 

 opposite plate. At first the amount of gold deposited is very 

 small compared with that dissolved from the positive pole, 

 the solution retaining the greater proportion ; but after some 

 hours, as the solution becomes saturated, the amount deposited 

 increases until there is a perfect balance. The solution is 

 now to be filtered and carefully evaporated ; it yields an abun- 

 dant crop of crystals of the double salt. In this way half an 

 ounce of gold may be dissolved in a few hours, and nearly an 

 ounce of the salt obtained. 



15. The salt obtained by either of these processes presents 

 the same general appearance and constitution. It crystallizes 

 in very minute octahedrons, which cluster together so as to form 

 long, jagged, irregular prisms, which again group round a 

 centre and form starlike masses ; they possess a peculiar bitter 



