president's address — SECTION B. 59 



Brisbane, who finds that 85 per cent, of the silver present in 

 low grade ores may be obtained in this way. 



Another process lately brought into use in Queensland and 

 in Victoria is the " Pollok Chlorination Process," more 

 especially adapted for gold ores. Chlorine under great pres- 

 sure is emjiloyed to dissolve the metal, the gold being 

 separated by an ii'on salt. The details of this process is 

 given by the late C. S. Wilkinson, who inspected its working 

 while in Glasgow about a year ago.* Mr. Wilkinson also 

 described the Macarthur- Forrest cyanide process, in which 

 a weak solution of ])Otassium cyanide is used to dissolve out 

 the precious metal, which is then I'emoved by metalhc zinc. 

 The process is being worked at Ravonswood, in Queensland. 



The chief considerations that have to be taken into 

 account in any of these methods of working must necessarily 

 include the question of easy transport across country of the 

 materials to be used, and the presence of an adequate water 

 supply. The future of silver reduction in Australia must 

 surely be an interesting one to all chemists and metallurgists ; 

 and when the labour question shall have been righteously 

 adjusted between man and man, and the spread of technical 

 education produces the skilled workman, there will l)e no 

 reason Avhy minerals carrying what are now considered 

 ridiculously small quantities of gold and silver should not be 

 economically worked. 



A promising step in the right direction is the idea of pro- 

 ducing chlorine on the spot from common salt by means of 

 the current of electi-icity from an ordinary dynamo. The 

 production of chlorine by electrolysis is already a fait accompli, 

 and bids fail' to j)rove successful as a commercial undertaking. 

 A process has been patented by Messrs. Richardson and 

 Holland, and recommends itself on the ground of its porta- 

 bility, the materials requisite for working the same being 

 easily transported over great distances. The principle is 

 based on the fact that common salt is decomposed and 

 resolved into its ions, as we have seen, the chlorine being set 

 tree next the anode and sodium at the kathode. The chloi'ine 

 is collected from the surface, while caustic soda remains in 

 the liquor. The chloi'ine may, however, be allowed to re- 

 unite with the sodium, as hypochlorite, if desired. A draw- 

 back to its use at first was the resistance caused by the 

 insertion of porous partitions used to separate the ions. This 



* Report, Mines Department for 1890, p. 213. Sydney : Government 

 Printer, 1891. 



