328 PROCEEDIXGS OF SECTION B, 



does not work satisfactorily, so that if not required for work it is 

 desirable to place it on closed circuit for about half an hour in 

 each twenty-four. For receiving the deposit of copper we use a 

 cathode formed of a platinum cylinder. The solution is plated 

 out in a beaker. The platinum cylinder is Ifin. high, liin. 

 diameter, about -iri-in- thick, and has riveted or soldered to 

 it a platinum wnre about -rein, diameter, 4|in. long, formed into 

 a hook at the upper end. The weight of such cylinder is 44grms. 

 The anode is formed of a piece of platinum wire iS.-in. diameter. 

 19in. long, of which about lOiin. is formed into a flat spiral with 

 the balance of the wire forming an upright stem rising from the 

 centre of the spiral; the upper enH of the wire is formed into a hook. 

 These hooks formed in the wire serve to suspend the cathode and 

 anode from their respective supports, and are preferred to binding: 

 screw attachments. The support for the cathode is so formed that 

 the weight of the cylinder tends to make good electrical contact. 

 The anode being comparatively light good contact is made by 

 means of a brass spring resting upon it and forming part of the 

 supporting arm. 



The beakers used meaure 4fin. high by 2Jin. diameter, and hold 

 about 9oz. The process is conducted as follows : — Igrm. of ore 

 is taken. 10 drops of strong sulphuric acid added, and a drop of 

 hydrochloric acid to precipitate any trace of silver, 10c. c. of strong 

 nitric acid added, watch glass put on, and the whole mixed by 

 gently twirling the beaker. It is then allowed to stand till 

 temperature has gone down, and then heated upon the steam bath 

 until all brown fumes have ceased to come off and all sidphur is 

 dissolved. If the heating is slow and the mixture not actually 

 boiled all the sulphur from an ore containing 25 per cent, sulphur 

 wall be readily oxidised. The cover and sides of the lieaker are 

 then washed down and the solution evaporated to dryness on the 

 steam bath, the cake broken up with glass rod and heated on sand 

 bath till fumes of svdphiu'ic acid come off. It is allowed to cool, 

 and 100c. c. of nitric acid added (Ipt. cone, acid to 120pts. water). 

 It is not necessary to filter from insoluble residue, but electrodes 

 may at once be placed in the solution and connected to the battery. 

 The wire anode should be placed as near bottom of beaker as 

 possible without actually toviching it, and the lower edge of 

 cylinder should he about ,^in. off the spiral. The cpiantity of 

 solution in the beaker should be such as to allow about ^in. of the 

 cylinder to remain above it. The time allowed for electrolysis 

 necessarily varies with the quantity of copper present, but twelve 

 hours is generally allowed for amounts up to -ogrm. By means of 

 a clock contact is made automatically at 9 p.m., or any other hour 

 for which it may be set, so that the estimations are finished by 9 

 next morning, 'ihe electrolysis should not be allowed to continue 

 for any long period after the copper is removed from the solution, 

 as the texture of the deposit is apt to be injuriously affected thereby. 



