200 Mr. J. Napier un Copper Smelting. 



tained in any ore or cupriferous product, by simply dissolving a 

 certain quantity (say 20 grains in nitric or nitromuriatic acid), 

 with the assistance of heat, if required, as in the case of some 

 suljihurets, the addition of ammonia in excess is necessary ; and 

 if any considerable quantity of iron or alumina was present in 

 the sample, it should be allowed to digest at a gentle heat, iinder 

 ebullition, to make sure that all the copper is taken up by the 

 ammonia; filter into a tlask, wash the precipitate with water, 

 and make into a bulk of 2500 grains, as when taking the stand- 

 ard of the solution of pure copper. All that now remains to be 

 done is to allow it to get cold, and add the cyanide of potassium 

 until decolorized, noticing the quantity taken. Suppose it 

 required 400 grains by volume of the cyanide solution ; then 

 from the proportion— 500 grs. K Cy : 10 Cu : : K Cy 400 : Cu8 

 — the quantity of copper contained in the 20 grains of material 

 taken for analysis, or 40 jier cent. If the ore taken was a sul- 

 phuret, it is sometimes advisable to filter, in order to separate 

 the sulphur before adthng the ammonia, or else to use a dilute 

 solution of ammonia, and a gentle heat when digesting, or small 

 particles of sulphuret of copper might be reproduced, especially 

 when the precipitate produced by the ammonia is a bitlky one." 

 These processes arc complicated, and liable to many sources 

 of error, and require an experienced chemist for their perform- 

 ance; while any process to be generally useful to the assayer 

 or smelter, should be easily performed, and the liability to 

 errors few. 



Depositing the copper from solutions by means of electricity 

 has also been recommended as a process for assaying. The 

 process is simply to get the copper into solution by digesting 

 the ore in acids, diluting and filtering, as already described; 

 in the filtered solution is placed a porous vessel of unglazed 

 earthenware filled with a solution of common salt or weak sul- 

 phuric acid, in which is immersed a piece of amalgamated zinc 

 or a piece of iron, connected by a copper wire with a small 

 piece of copper previously weighed, which is put into the copper 

 solution. The porous cell should be so placed that the piece of 

 copper be under it. Galvanic action begins between the copper 

 and zinc, and the copper held in solution is deposited in the 

 metallic state upon the slip of copper ; the action is allowed to go 

 on until all the copper is extracted from the solution, which may 

 be known by taking out a drop and touching it with ammonia, 

 which if copper be present gives a blue colour ; or by dipping 

 into the solution a blade of a knife, which will take a copper 

 colour if any of that metal remain in solution. When the opera- 

 tion is finished, the ])iece of copper is again weighed; the in- 

 crease of weight is due to the copper that was in the solution. 



