194 



The Philippine Journal of Science 



1916 



When stripped by immersion in boiling sodium peroxide solu- 

 tion ^^ samples of the same tin gave the following results : 



Table II. — Analysis of tin plate by the Meyer method. 



No. 



Weight 



of 

 aample.a 







Coating per unit 

 area. 



Loss after treat- 

 ment. 



Per 

 square 

 deci- 

 meter. 



Per 



square 

 foot. 



6 



Grams. 

 4.346 

 4.360 

 4.289 

 4.310 



Grams. 

 0.082 

 0.085 

 0.078 

 0.075 



Per cent. 

 1.89 

 1.95 

 1.82 

 1.74 



Grams. 

 0.328 

 0.340 

 0.312 

 0.300 



Ounces. 

 0.107 

 0.111 

 0.102 

 0.098 



7 _ 



8 . . 



9. . . .._ _.. 



Average 



4.326 



0.080 



1.85 



0.320 



0.1045 





" Size of samples, 5 by 5 centimeters. 



The Meyer method gives concordant and reliable results, but 

 it is clumsy, because of the unavoidable and disagreeable spat- 

 tering attendant on the use of sodium peroxide, and because 

 long and repeated treatment is necessary to ensure complete 

 removal of the coating. 



The results obtained by this method are higher than those 

 obtained by direct analysis of tin, the difference (about 0.05 

 gram) representing the amount of iron removed with the tin 

 plate. That this iron is actually part of the alloy and is not 

 due to attack on the base is shown by the fact that there was 

 no further loss in weight on subsequent treatment with sodium 

 peroxide. 



Since iron is an insoluble anode in certain alkaline and oxid- 

 izing solutions, other metals can readily be stripped from it 

 electroljrtically.2" For the work here recorded a 30 per cent 

 solution of sodium nitrate was employed as stripping bath, and 

 the plate was made the anode. As will be seen, the results 

 obtained are comparable with those obtained with sodium per- 

 oxide. Comparable results were obtained with sodium or potas- 

 sium hydroxide solutions, but with these the action was so slow 

 that their use is not recommended. 



' Meyer, op. cit. 

 Cf. Burgess, C. F., Trans. Am. Electrochem. Soc. (1903), 4, 31. 



