250 ELECTROLYSIS. 



The inventors quote, as an example, a bath of plumbic 

 nitrate in which were a galena anode and an insoluble metal 

 cathode. 



The reactions which take place are the following ones : 



Pb (N0 6 ) 2 = Pb + (N0 6 ) 2 . 

 PbS + (N0 6 ) 2 = Pb + (N0 6 ) 2 + S. 



The lead under the action of the current goes to the cathode, 

 and the acid on to the anode, where it attacks the galena and 

 regenerates the plumbic nitrate. The bath remains constant 

 and neutral, and may be indefinitely used. The acid of the 

 salt escapes from the action of the current, since it only comes 

 out of one combination to enter into another. The sulphur can 

 easily be extracted, since it is separated. Polarisation is in 

 a great proportion avoided owing to the absence of gaseous 

 escapes. 



Messrs. Bias and Miest's process comprises two distinct 

 operations: 1st, the agglomeration of the ores; 2nd, the 

 electrolysation. 



The agglomeration is obtained by heat and compression. 

 The ore, crushed into grains of about 5 millimetres diameter, is 

 introduced into copper moulds and submitted to a pressure of 

 about 100 atmospheres, then closed and heated in a furnace at 

 about 600 C. ; then pressed again on coming out of the furnace ; 

 and lastly, rapidly cooled for facilitating the taking to pieces 

 of the plates. 



Thus prepared, the ore plates are attached to some iron 

 bars, which are connected by means of iron conductors to the 

 positive pole of a dynamo-electric machine and suspended in 

 the bath. The latter is formed by the solution of a neutral 

 metallic salt suitable for the nature of the ore to be treated. 

 For galena, the solution, as a matter of course, is plumbic 

 nitrate; for blende it is the nitrate, sulphide or chloride of 

 zinc, and so on. If the ore is compound, the solution is selected 

 in accordance with the various metals which enter into its 

 composition. 



The cathodes are composed of plates of metal insoluble in 



