142 



The Philippine Journal of Science 



1916 



chromium nitrate, there was no noticeable attack on the iron 

 base on continued passage of current. 



The results of the foregoing experiments indicate that many of 

 the methods enumerated are capable of being used for quanti- 

 tative analyses ; hence some of the more promising were studied 

 in greater detail. For these experiments samples of the same 

 galvanized iron (different from that used in the foregoing tests) , 

 cut with shears as accurately as possible into square of desired 

 size, were used. 



The results recorded in Table IV were obtained by making 

 galvanized iron the anode in 30 per cent sodium nitrate solution. 



Table IV. — Stripping of galvanized iron with an electric current. Galva- 

 nized sheet anode, platinum cathode. Bath, SO per cent sodium nitrate 

 (NaNOs) solution, except as noted; current, 0.7 to 1.0 ampere; voltage, 

 S to 5; size of plate, 3.8 by 3.8 centimeters {1.5 by 1.5 inches), except as 

 noted. 



Exper- 

 iment 

 No. 



Sample. 







Weight of coating. 



Loss. 



Per 



square 

 foot. 



Per 

 square 

 deci- 

 meter. 



42 

 43 

 44 

 46 

 46 

 47 



Gram^. 



8.232 

 7.948 

 8.345 

 8.(18 

 »83.175 

 b8.068 



Grams. 

 1.203 

 1.201 

 1.217 

 1.186 

 4.650 

 1.127 



Per cent. 

 14.61 

 15.10 

 14.93 

 14.26 

 14.02 

 13.97 



Ounces. 

 2.73 

 2.72 

 2.76 

 2.69 

 2.64 



Grams. 

 8.33 

 8.31 

 8.43 

 8.21 

 8.07 







■■> This sample was 7.6 by 7.6 centimeters (3 by 3 inches), 

 b In a bath of 20 per cent sodium hydroxide 



Only a few minutes were necessary completely to remove the 

 zinc from the iron. There was no residual zinc on the stripped 

 plate. The results obtained show as good agreement as could 

 be expected, considering the lack of uniformity of zinc coatings, 

 the size of the samples used for analysis, and the errors incident 

 to cutting out squares with ordinary tin shears. 



The presence of iron could always be shown in the solution 

 after stripping had been accomplished. That this was not due 

 to an appreciable extent to attack on the iron base is shown 

 not only by the constancy of the results recorded for the thick- 

 ness of the coating, but also by the constancy of the amount of 

 iron removed in the different trials. Duplicate determinations 

 fixed the amounts of iron from pieces of galvanized iron 3.8 by 

 3.8 centimeters (1.5 by 1.5 inches) as 0.046 and 0.048 gram, 



