144 



The Philippine Journal of Science 



1916 



(Table IV) for the same galvanized iron shows clearly that this 

 iron was part of the zinc-iron alloy, not part of the iron base. 

 However, as might be expected, the rate of solution of zinc is 

 somewhat retarded by this process. The separation is completed 

 in a very few minutes, and the iron base, so far as could be deter- 

 mined, is protected. 



Finally a series of determinations was made, using different 

 acids of varying concentrations. The results, which are self- 

 explanatory, are given in Table VI. 



Table VI. — Stripping of galvanized iron with acids. Temperature, 30° C. 

 Size of samples, 3.8 by 3.8 centimeters {1.5 by 1.5 inches). 



Exper- 

 iment 

 No. 



Bath. 



Sample. 







Weight of coating. 



Loss. 



Per 

 square 

 foot. 



1 

 Per 

 square 

 deci- 

 meter. 



53 



54 



55 

 56 



Sulohuric acid, 2 per cent, plus ar- 

 senic trioxide _ 



Grams. 



8.128 



8..S36 

 8.102 

 7.941 



Grams. 



1.015 



11.122 

 » 1.128 

 b 1. 099 



Per cent. 



12.48 



13.49 

 18.92 

 13.84 



Ounces. 



2.30 



2.55 

 2.56 

 2.49 



Grams. 



7.03 



7.77 

 7.81 

 7.61 



Phosphoric acid, 26 per cent by vol- 

 ume _ - . _- 



. . do - 



Hydrochloric acid (sp. gr., 1.19) 



* No additional loss after reimmersion for one hour. 



•> Loss <0.002 gram after thirty minutes additional immei-sion. 



In each case the removal of zinc is characterized by efferves- 

 cence, which ceases entirely when the iron of the base is reached. 

 Phosphoric acid reacts slowly, but the stripped iron can be left 

 immersed for a long time without appreciable loss. 



DISCUSSION 



The experiments here enumerated, -^ aside from their possible 

 application to analytical or commercial problems, are of interest 

 in their bearing on the question of the potentials of metals in 

 different baths and the replacement of a metal from its salts by 

 another metal. That the replacement series of the metals differs 

 not only in solutions of different substances in a given solvent, 

 but also in solutions of the same substance in a constant sol- 

 vent with factors such as change of temperature, pressure, con- 

 centration, magnetic influence, and the like is well known.^^ 



" The applicability of some of the methods enumerated above to the 

 removal of tin from tin plate will be discussed in another paper. 



"Cf. Gore, G., loc. cit.; idem, Proc. Roy. Soc. (1879), 30, 38; Christy, 

 S. B., Trans. Am. Inst. Min. Eng. (1900), 30, 864. 



