THE DETINNING AND ANALYSIS OF TIN PLATE ^ 



By George W. Heise and AmAndo Clemente 



(From the Laboratory of Genei'al, Inorganic, and Physical Chemistry, 



Bureau of Science, Manila, P. I.) 



INTRODUCTION 



Practically all the tin plate on the market is made by a hot-dip 

 process — ^by immersing carefully gleaned sheet iron in a bath 

 of molten tin. The coating formed by this process varies from 

 almost pure ,tin at the outer surface of the plate to a tin-iron 

 alloy rich in iron near the surface of the iron base. Often 

 varying amounts of lead are used in the molten bath. 



The removal of the coating from tin plate, both for the com- 

 mercial recovery of tin and for analytical purposes, has been 

 the subject of much study. Among the commercial methods 

 the most important are the electrolytic detinning in alkaline 

 solution,^ the chlorine process,^ and various modifications of 

 these.* 



In addition, a large variety of methods have been proposed, 

 such as the mechanical separation of tin from tin plate by 

 agitation of a mass of tin scrap with liquid air ; ^ the treatment 

 of the material with superheated steam,* whereby tin is fused 

 and loosened by the formation of iron oxides; solution of tin 

 in strong commercial hydrochloric acid, kept cold ^ to prevent 

 the solution of iron; removal of tin by a solution of sodium 

 plumbate ; * or electrolysis in a bath of phosphoric acid.^ 



Many processes ^" have been recommended for the removal 

 and determination of tin and lead in tin plate, among 



^ Received for publication July 17, 1916. 



'Keith, U. S. Patent 176,658 (1876). 



' Cf. Electrochem. & Met. Ind. (1909), 7, 79. 



■* Skinner, R. P., German detinning methods, Det. Ind. (1914), 12, 

 236. Detinning industry, Electrochem. & Met. Ind. (1909), 7, 79. 



'Phelps, W. J., U. S. Patent 952,351 (March, 1910). 



'Wiltereck, H. C, German Patent 261,522 (February, 1912). 



'Calmels, J. M., French Patent 448,004 (September, 1902). 



'Ramage, A. S., Met. & Chem. Eng. (1911), 9, 219. 



'Battle, A. E., Brit. Patent 14,514 (June, 1914). 



" Cf. Serger, H., Zeitschr. f. d. Untersuch. d. Nahrungs- u. Genussm. 

 (1913), 25, 465. 



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