138 



The Philippine Journal of Science 



1916 



sists in boiling weighed pieces of galvanized iron with sodium 

 peroxide and water and determining the loss in weight. Typical 

 analyses follow: 



Table I. — Analyses of galvanized iron by the Meyer method. 



Sample.s 



Loss after treat- 

 ment No. — 



Coating 



in sam- 



ple.fa 



Weightof coating, b 



No. 



Weight. 



I. 



II. 



Per 

 square 

 foot. 



Per 

 square 

 deci- 

 meter. 



1 

 2 

 3 



4 



Grams. 

 14.480 

 14.912 

 14. 483 

 14.827 



Grctwis. 

 0.877 

 0.842 

 1.531 

 1.507 



Grams. 

 1.526 

 1.556 

 1.543 

 1.530 



Per cent. 

 10.52 

 10.42 

 10.35 

 10.64 



Ounces. 

 1.94 

 1.97 

 1.95 

 1.94 



Grams. 

 5.92 

 6.03 

 5.98 

 5.95 



■ Each sample was 5.08 by 5.08 centimeters (2 by 2 inches). 

 " Computed from loss of weight after second treatment. 



The Meyer method gives concordant and reliable results. 

 However, it was devised especially for the stripping of tin plate 

 and is better adapted to that process than to the stripping of 

 galvanized iron because of the relatively large amounts of zinc 

 used for coating iron. Treatment with sodium peroxide must 

 be repeated several times to insure the complete removal of the 

 zinc coating from ordinary galvanized iron, so that the process 

 becomes tedious. 



Some of the experiments performed in the course of this study 

 have little analytical or commercial value at present, but yield 

 interesting information regarding the potentials of metals in 

 various solution. We have divided them into two classes — 

 namely, those in which the zinc has been dissolved by immersion 

 in the stripping solution and those in which electric current 

 has been used to aid or control the action. 



Table II gives examples of stripping baths of the first class. 

 For the tests enumerated, pieces were cut from a sheet of gal- 

 vanized iron, which analysis had shown to be fairly uniform 

 in composition. Therefore the results obtained may be con- 

 sidered comparable. As galvanized iron at best is of varying 

 composition, differences of less than 0.1 per cent have little 

 significance. A few tests by standard methods (Nos. 5, 16, etc.) 

 are inserted for comparison. 



