﻿38 



IXDTAXA rXIVEESITY 



material. The anodes were suspended with platinum wires to avoid 

 a slight contamination with copper which resulted when copper 

 wires were used. The copper connecting wires, Avhile not attacked 

 very rapidly, nevertheless become appreciably smaller after being 

 used for a long time in making connections to the anode. This 

 might be avoided if the copper Avere cast into the anodes and not 

 merely hooked through holes. The fact that these copper wires, in 

 contact with the anodes, are only very slightly attacked gives a strik- 

 ing visible proof that lead may be easily purified from copper. 



The analyses show that the refined lead from very impure bullion 

 contains only minute quantities of impurities. These impurities^^ 

 are. for the most part, due to the method of circulating the solution 

 by a current of gas. This stirs up the slime from the bottom, some 

 of which adheres to the cathode. 



The slime contains only a small amount of lead. This is im- 

 portant, because it simplifies the subsequent treatment for the re- 

 covery of the valuable metals which are in the slimes. 



Loss of Perchloric Acid. Some of the electrolyte is always 

 mechanically trapped or held within the metal of the cathode. The 

 loss of perchloric acid caused by this was determined by fusing 

 portions of the cath(>des with sodium nitrate. This treatment de- 

 composes the perchlorate into chloride.^' The chlorine was deter- 

 mined by Volhard's method and was calculated into perchloric acid. 

 The results are: 



Gms. of Gms. of Chlorine Per Cent 



Cathode in Terms of T^nss of 



Used. Perchloric Acid. Perchloric Acid. 



Very smooth cathode 2.5. 0.0041 0.018 



Very rough cathode IS. 0.0035 0.02 



This represents a loss of about 0.4 pounds of perchloric acid per 

 ton of lead deposited. 



The perchlorate baths which had been used for months, did not 

 give any test for chlorides with sih^r nitrate. This shows that 

 there is no loss of perchloric acid by slight reduction. 



The slime, even after careful washing, contains some of the 

 perchlorate of the bath. One sample of slime showed 1.1 per cent, 

 of perchloric acid. This result includes the chlorine from chlorides 

 calculated to perchlorate. Some chlorine had come, perhaps, from 

 the dust and fume of the laboratory. These chlorides, during elec- 

 trolysis, would unite with the silver of the anode and thus remain 

 111 the slime. The total loss of perchloric acid in the slime repre- 



I'JKern, Transactions American Electrochemical Society^ VI, 39 (1904). 

 ^7 Mathers, Journal American Chemical Society, XXXII, 66 (1910). 



