XI, A, 4 Heise and Clemente: Galvanized Iron 137 



the attack on the iron of the base is so slight that it may be 

 disregarded. Bauer " takes advantage of the frequently record- 

 ed " inhibitive effect of arsenic on the dissolution of iron in 

 sulphuric acid to recommend the addition of arsenious acid to 

 dilute (2 per cent) sulphuric acid in making the separation. 



Hydrochloric acid is capable of similar utilization. The follow- 

 ing analytical data (Tables II and V) show that concentrated 

 hydrochloric acid can be used for stripping without appreciable 

 effect on the iron of galvanized sheet, while Witt ^^ recommends 

 the use of dilute hydrochloric acid. Aupperle '* suggests the use 

 of concentrated hydrochloric acid (specific gravity, 1.2) with 

 an addition agent, antimony trichloride (SbClg), to protect the 

 iron. In this case the action is probably similar to the inhib- 

 iting effect of arsenious acid on the action of sulphuric acid.^* 



Alkalies also can be used. Walker ^® reports that the zinc 

 of galvanized iron, exclusive of the zinc-iron alloy, may be re- 

 moved quantitatively by dissolving in a hot caustic soda solution. 

 The use of hot sodium peroxide solution is recommended by 

 Meyer.^^ 



There are several other stripping solutions mentioned "' 

 in the literature, although most of these do not yield sufficiently 

 accurate results to serve in analytical methods, or have not 

 been developed for analytical purposes. 



EXPERIMENTAL PART 



The first method to be tested in the present series of exper- 

 iments was that of Meyer.^* Briefly stated, this method con- 



" Bauer, 0., Mitt. kgl. Materialprilfungsamt (1914), 32, 448. 



"Millon, E., Compt. rend. Acad. Set. (1845), 21, 37; Burgess, C. F., 

 Tratis. Am. Electrochem.. Soc. (1905), 8, 165; (1906), 9, 199. For a 

 possible explanation for this phenomenon see Watts, 0. P., ibid. (1912), 

 21, 337. 



"Witt, J. C, This Journal, Sec. A (1916), 11, 154. 



"Aupperle, J. A., Metal. Ind. (1915), 13, 329; Iron Age (1915), 96, 132. 



"Beneker, U. S. Patent 914,916 (March, 1909), uses dilute hydrochloric 

 acid containing from 0.001 to 0.005 per cent arsenic as a cleaning or 

 pickling bath for iron or steel. 



" Loc. cit. 



"Meyer, K., Zeitschr. f. angew. Chem. (1909), 22, 68; Serger, H., 

 Zeitschr. f. Untersuch. d. Nahrungs- u. Gemissmittel (1913), 25, 465. 



''Broemme, E., and Steinau, R., U. S. Patent 1,042,315 (October, 1912). 

 The use of alkali or alkaline earth bisulphates or bisulphites; the use of 

 zinc chloride in slightly basic water solution; Weber, U. S. Patent 1,122,272 

 (December, 1914). 



" Loc. cit. 



