XI, A, 4 Heise and Clemente: Tin Plate 



Table III. — Analysis of tin plate by electrolysis.' 



A. IN A 80 PER CENT SODIUM NITRATE SOLUTION. 



195 



No. 



Weight 



of 

 sample. >> 







Coating per unit 

 area. 



Loss after treat- 

 ment. 



Per 

 square 

 deci- 

 meter. 



Per 



square 

 foot. 



10 _ 



Grams. 

 4.346 

 4.281 

 4.261 

 4.296 



Gram,s. 

 0.082 

 0.080 

 0.079 

 0.080 



Per cent. 

 1.88 

 1.87 

 1.85 

 1.84 



Gram^. 

 0.328 

 0.320 

 0.316 

 0.320 



Ounces. 

 0.108 

 0.105 

 0.104 

 0.105 



11 



12 



13 





4.296 



0.080 



1.86 



0.321 



0.105 





B. IN A 20 PER CENT SODIUM HYDROXIDE SOLUTION. 



14 - , 



4.337 

 4.292 



0.072 

 0.078 



1.66 

 1.84 



0.288 

 0.302 



0.094 



15 



0.102 [ 







" Voltage, 3.5 ; amperage, 0.7 ; time, about ten minutes. 

 ■> Size of samples, 5 by 5 centimeters. 



This procedure offers an extremely simple and rapid method 

 of analysis. Stripping is accomplished in a few minutes. There 

 is no danger of attacking the iron of the base. The iron of the 

 alloy removed from the plate is left in the bath in such form 

 that it can be readily recovered as ferric hydroxide and can be 

 determined quantitatively. 



By reference to the results obtained in Table II it is evident 

 that the two methods are strictly comparable. 



In a study of the stripping of galvanized iron, we called at- 

 tention ^^ to a number of salts which would be replaced in solution 

 of metals by zinc but not by iron. As zinc is generally elec- 

 tropositive to iron in aqueous baths, metals intermediate in the 

 potential series to zinc and iron should form salts which strip 

 zinc from iron. Such salts were readily found, among them 

 a number which might have been expected to attack iron as 

 well as zinc. To find salts which will strip tin from iron is 

 more difficult, since tin is electronegative to iron in many aqueous 

 solutions, and salts which dissolve the former might naturally 

 be supposed to attack the latter. 



T/ms Journal, Sec. A (1916), 11, 144. 



