196 



The Philippine Journal of Science 



1916 



Basic lead acetate solution will strip zinc from iron,*^ j^^^ 

 leaves tin plate unattacked. Lead acetate does not affect tin 

 plate either in neutral or (acetic) acid solution, but lead acetate 

 or other lead salts, in solutions made alkaline with sodium or 

 potassium hydroxide, strip tin from plated iron very rapidly, 

 depositing lead in a spongy, easily removed condition. The 

 accuracy of the method may be judged by the tests made on 

 samples of the same tin plate previously analyzed. 



Table IV. — Analysis of tin plate by immersion in alkaline lead acetate 



(sodium plumbite) solution. 



FIVE-MINUTE TEST. 



No. 



Weight 

 of sam- 

 ple.* 







Coatingr per unit 

 area. 



Loss after treat- 

 ment. 



Per 



square 

 deci- 

 meter. 



Per 



square 



foot. 



16 . 



Grams. 

 4.285 

 4.214 

 4.221 

 4.325 



Gram,s. 

 0.078 

 0.076 

 .0. 072 

 0.073 



Per cent. 

 1.82 

 1.80 

 1.70 

 1.69 



Grains. 

 0.312 

 0.304 

 0.288 

 0.292 



Ounces. 

 0.102 

 0.100 

 0.094 

 0.096 



17 



18 



19 





Averagre 



4.261 



0.075 



1.75 



0.299 0.098 



THREE-DAY TEST. 



16._- 



4.285 

 4.214 

 4.221 

 4.325 



0.082 

 0.082 

 0.077 



1.91 

 1.95 

 1.85 



0.328 

 0.328 

 0.808 



0.107 

 0.107 

 0.101 



17 



18 



19 



Average 













4.261 



0.080 



1.90 



0.321 



0.105 





' Size of samples, B by 5 centimeters. 



These data are again comparable with those obtained by the 

 methods previously outlined. Concordant results are obtained, 

 and unless great refinement is desired, the method is sufficiently 

 rapid and accurate to serve as a reliable guide in the judgment 

 of tin plate. Compared with the data previously recorded, the 

 results obtained with alkaline lead acetate solution are a trifle 

 low, showing that all of the tin-iron alloy is not removed im- 

 mediately by this method. As a matter of fact, the lead solu- 

 tion does strip nearly all of the iron-tin alloy from the iron if 

 the time of immersion is prolonged, the reaction being practically 



"Patrick, W. A., and Walker, W. H., Journ. Ind. & Eng. Chem. (1911), 

 3, 239. 



