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INDIANA UNIVERSITY 



4. Studies on Perchloric Acid : Electrodeposition op Lead 



FROM PeRCHLORATE BaTHS. 

 By Frank C. Mathers, Assistant Peofessor of Chemistry. 



General Statement. The electrolysis of most solutions of lead- 

 salts gives a loose crystalline deposit upon the cathode, which is 

 valueless for refining or plating purposes. Betts has patented^ the 

 use of a lead fluo- silicate bath containing free fluo-silicic acid and 

 small amounts of gelatine or glue. This bath gives dense, non- 

 crystalline deposits which are commercially valuable.- Without 

 the glue or gelatine, loose crystals are formed, such as are charac- 

 teristic of the nitrate or acetate baths. ''Fluo-silicic acid has some 

 specific property not possessed by the nitrate and acetate solutions, 

 and the s'^lid deposit is not the result of the gelatine alone. The 

 addition of gelatine to acetate or nitrate baths does not give satis- 

 factory deposits.* 



The author^ has found that a solution of lead perchlorate con- 

 taining some free perchloric acid and a small amount of an addi- 

 tion substance, such as glue, tannin, licorice, but preferably pep- 

 tone, works very satisfactorily as an electrolyte for the plating or 

 refining of lead. Cathode deposits may be obtained over an inch in 

 thickness, very smooth and of a density 11.36. 



1 ead perchlorate, Pb (CIO J o.oIIoO, possesses many properties 

 that are ideal for making electro-plating or refiTing baths. It is 

 "extremely easily soluble in water — one part of salt dissolving in 

 about one part of water. Its great solubility permits the mak- 

 ing of solutions of any desired concentration without danger of the 

 crystallization of saHs. It is not decomposed by boiling, by alkalies, 

 by acids or by electrolysis. It is unacted* upon by the air, and 

 cannot be reduced by nascent hydrogen — not even by the zinc- 

 copner couple. It can only be decomposed by fusion with sodium 

 carbonate or with sodium nitrite. It does not easily give basic 

 salts. "When electrolyzed, it give's dense, solid deposits upon the 

 cathode. The efficiency of corrosion of the anode and of deposition 

 on the catliode is nearly tlieoretical, so the composition of the bath 



lU. S. Patent, 713, 278. 



2 Betts, Electrochemical Metallurgical Inrlnstry, I, 407 (1903). 

 TJlke, Engineerinp Mining Journal, Oct. 11, 1002. 



8 Senn, Zeilachrifi fiir Electrocfiewie, April 14, 1905. 



Kern, Transactions American Electrochemical Society, XV, 454 (1909). 

 «U. S. Patent, 931, 944 (1909). 

 8 Corney, "Dictionary of Chemical Soliihilities." 



Note. — This paper was presented at the Seventeenth General Meeting of the 

 A^merican Electrochemical Society, at Pittsbur,?, Pa., May 7, 1910. 



