366 Mr. J. Napier on the Solubility of the 



the purpose of trying experiments upon this subject, I was 

 kindly favoured with a quantity of the water, with the follow- 

 ing details : — Quantity of water issuing from the mines yearly, 

 700,000,000 gallons ; this is collected in pits, into which is put 

 old iron, which precipitates the copper. The average pro- 

 duct of copper is from 55 to 60 tons; the iron consumed in 

 obtaining this is 600 tons. The copper found in these waters, 

 as indicated from the precipitate obtained, varies from 4 to 

 30 per cent., according to the wetness of the season ; the sam- 

 ple I procured was during the dry season, and consequently 

 rich in copper; its specific gravity was 1*05.5 at 60° F. The 

 solid contents of one gallon weighed 4960 grains, which gave 

 peroxide of iron 1680 grains, oxide of copper 80 grains, sul- 

 phuric acid 3040 grains, muriatic acid 38 grains, and 122 

 grains of earthy matters, which were not examined. The iron 

 existed in the water as the persulphate. My first operation 

 was one I had found to answer in analysing copper ores, 

 namely, wrapping a strip of brown paper round a piece of 

 iron, attaching this to a piece of copper, and immersing them 

 both in the solution of the copper ore, in muriatic acid, to be 

 examined ; but I found that the first action which took place 

 was the complete reduction of the persalt of iron to the state 

 of protosalt, at the expense of the copper pole: after which 

 the electric current began to effect its object, the copper being 

 deposited, but from the copper which had been dissolved 

 having also to be deposited, the consumption of iron was 658 

 grains, while the actual increase in the weight of the copper 

 pole was only 64 grains, the quantity of copper originally held 

 in solution. The reaction which took place may be expressed 

 as follows : — 



1/?ork • c firon 582*7" 



1680 grains of . _-„ ' 



•5 c . J iron 582*7 i r* 



peroxide of iron<( ^ > protosulphate of iron. 



composed of I ox ^S e x I 



Loxygen 171 '5. 



oxygen 171*5 V 

 2568 grains of f ac ! 1 } ^6*0 f 



sulphuric acid. 1 acK * & *°J 



^ Lacid 856*01 i u <. e 



Copper pole. copper 690*7 j Sul P hate of C0 PP er ' 



giving 690*7 grs. + 64 grs. to be deposited by the electric cur- 

 rent. Different arrangements of batteries were tried; platinum, 

 silver and lead were also substituted for the copper, but in no 

 case was a deposit obtained from the water until the iron was 

 first brought into the state of a protosalt; but when this was 

 effected, I obtained by the method first described 63 grains of 

 copper by the loss of 58 grains of iron. 



