XI. A, 4 Witt: Testing of Galvanized Iron 159 



as the coating has entirely disappeared, the sheet is removed 

 and rinsed, allowing the water to run into the tray. The con- 

 tents of the tray are then rapidly transferred to a large beaker, 

 containing from 400 to 500 cubic centimeters of recently boiled 

 water and about 100 cubic centimeters of titrating solution.^" 

 The iron is then titrated with fifth normal permanganate (using 

 a 100 cubic centimeter burette). The error in such a deter- 

 mination is probably due to the fact that a portion of the iron is 

 oxidized by contact wtih the air before the titration is made 

 and that the comparatively high concentration of hydrochloric 

 acid present interferes to some extent with the end point. This 

 determination requires less than five minutes, while the gravi- 

 metric method requires from one to two hours. 



VARIOUS BRANDS TESTED 



All results given above were obtained by tests on samples 

 cut from the same large sheet of galvanized iron. This was 

 done so that the samples might be as nearly uniform as possible 

 and thus afford a sound basis of comparison. It was realized, 

 however, that the method would be worthless unless it would 

 give equally satisfactory results with products of various mills. 

 Accordingly the test has been applied to five different brands 

 of galvanized sheeting. Four of them were made in the United 

 States and one in England. Two squares were cut from each 

 sheet, properly cleaned and weighed, and the total loss in hy- 

 drochloric acid was determined. In each case, after the square 

 Was removed, the acid and washing were placed in a liter flask, 

 made up to the volume and were analyzed for iron by the 

 gravimetric method. The stripped squares were then placed 

 in hydrochloric acid and allowed to remain for twenty minutes. 

 They were removed, washed, dried, and reweighed. 



It is evident that the iron dissolved from the base itself is 

 negligible. This is true in all the results given in this paper 

 as well as in a number of other brands which have been tested 

 from time to time. The alloyed iron is nearly always less than 

 the minimum variation of the coating between samples of the 

 same sheet and can usually be neglected. It seems peculiar 

 that the total alloyed iron per square foot for all the brands 

 tested should be so uniform, when there is such a wide variation 

 in total coating. 



" See Olsen, J. C, Quantitative Chemical Analysis. D. Van Nostrand Co., 

 New York (1908), 319. 



