150 E. F. ROEBER 



conditions dense solid cathodic deposits of metals are obtained. 

 The simple method, by which in the case of lead Betts over- 

 comes all difficulties in this respect— by providing a reducing 

 action, practically accomplished by the addition of gelatine or 

 glue — seems very encouraging. 



As the reverse case of electroplating, we may consider 

 the electrolytic stripping of metals. The production of 

 tin from tin scrap has achieved considerable commercial 

 success, first in several plants in Germany, from where it 

 was recently imported to this country. An interesting sim- 

 ilar process, although of much less industrial importance, is 

 the method of Burgess, which was used in bicycle manufac- 

 turing works for removing the thin layer of brass on the sur- 

 face of the frames by electrolysis, with a sodium nitrate solu- 

 tion as electrolyte. This example is mentioned to show how 

 electrochemical methods may be applied to details in various 

 manufacturing processes and may effect an important econ- 

 omy of labor. 



In their application to the metallurgy of gold, the use 

 of electrolytic methods has been confined to the cyanide proc- 

 ess, as far as commercial success has been obtained. Elec- 

 trolytic precipitation has been used successfully in the Sie- 

 mens & Halske process in South Africa, although side by 

 side with zinc precipitation. The latter method is nearly 

 exclusively used in this country. But it should not be over- 

 looked that the latter method is also essentially an elec- 

 trochemical phenomenon. Chemically pure zinc is inactive 

 as a precipitating agent. What is needed is commercial 

 zinc containing small particles of impurities, or specially 

 prepared zinc couples, like zinc lead. Thus, while with 

 electrolytic precipitation we have the source of the electric 

 current outside of the precipitating vat, we have with zinc 

 precipitation an immense number of small short circuited gal- 

 vanic couples in the precipitating vat itself. 



In the production of metals from ores, much research 

 has been devoted to the problem of getting copper and nickel 

 from the Sudbury ores. The late Dr. Hoepfner did highly 

 valuable pioneer work in this line, but full commercial suc- 

 cess was obtained by David H. Browne, who, in working out 



