162 



The Philippine Journal of Science 



1916 



Table VII. — Zinc and iron dissolved from a sheet of galvanized iron, 



minute by minute. 



[Initial temperature, 30.5° C. ; final temperature, 37.5° C. ; volume of acid, 1,000 cubic centi- 

 meters ; concentration of acid, 10.55 per cent HCI.] 



Time. 



! 



Total 

 zinc. 



Total 

 iron. 



Zinc per 



square 



foot. 



Iron per 



square 



foot. 



Fe 



Zn+Fe 



Min. 



Grams. 



Grams. 



Ounces. 



Ounces. 



Per cent. 



1 



4.3280 



0.0280 



0. 6102 



0. 0039 



0.64 



2 



12.0812 



0. 0924 



1.7034 



0. 0130 



0.76 



3 



15. 4214 



0. 1780 



2. 1744 



0. 0251 



1.51 



4 



16. 6165 



0. 5224 



2.3429 



0. 0737 



3.05 



5 



16. 8109 



0. 5728 



2. 3703 



0. 0808 



3.30 



6 



16. 8109 



0. 6586 



2.3703 



0. 0929 



3.77 



7 



16. 8245 



0. 6967 



2. 3723 



0. 0982 



3.98 



8 



16. 8278 



0. 7313 



2. 3727 



0. 1031 



4.16 



9 



16.8502 



0.7358 



2.3769 



0. 1037 



4.18 



10 



16.8998 



0.7358 



2.3828 



0. 1037 



4.18 



These values were used in plotting the solution velocities of the 

 zinc and the iron against the time (fig. 2). 



Discussion of results. — The iron in a hot-galvanized sheet is 

 present as follows : 



1. The spelter itself before being placed in the bath contains 

 traces of iron. 



2. The spelter is gradually contaminated with iron from the 

 walls of the bath and from iron sheets or other articles that 

 are passed into it. 



3. Alloys are formed on the immersed sheet by the action 

 of the molten zinc. 



4. The base is, of course, nearly all iron. 



The various steps in the action of hydrochloric acid on a gal- 

 vanized plate may be clearly seen from the results. The acid 

 at first comes into contact with the zinc, which contains only 

 the iron present in the spelter when the sheet was placed in the 

 galvanizing bath. The reaction is very rapid, and during the 

 first three minutes 91.25 per cent of the total zinc present passes 

 into solution. During the same period only 24.20 per cent of 

 the total alloyed iron dissolves. During the next three minutes 

 8.22 per cent more of the zinc and 65.38 per cent more of the 

 iron dissolve. The remainder of the time the reaction is very 

 slow, only 0.53 per cent of zinc and 10.42 per cent of the iron 

 being dissolved. The great variation of the percentage of iron 

 in the total metal dissolved is given in the last column of the 

 table. Still greater variation is observed if the percentages 



