XI, A, 4 



Witt: Testing of Galvanized Iron 



157 



The choice of the most satisfactory concentration is easily 

 made. The action of the concentrated acid is too violent and 

 results in dissolving some iron from the base. For that reason 

 it may be eliminated. The other two concentrations are equally 

 adapted to the work in that they both remove all the zinc 

 with the minimum amount of iron. Since the 1.098 density 

 acid acts more rapidly than the other and apparently has no 

 disadvantage, it is considered the best. It is possible that an 

 acid might be found some place between densities 1.098 and 1.190 

 which would act more rapidly without dissolving any more iron, 

 but the former seems to answer every requirement. It is also 

 possible that with some grades of galvanized iron it might be 

 better to use a slightly weaker acid. 



Having determined the best concentration of acid, it was 

 next necessary to investigate the influence of temperature on 

 the solution velocity of the iron base. Previous experiments had 

 shown that if a 15-centimeter square of sheeting were left in the 

 acid at room temperature for many minutes the loss in weight 

 was negligible. This work was extended to include temperatures 

 between 30° and 100°C. Each piece was left in the acid (at 

 a given temperature) for twenty minutes, removed, washed in 

 water and then in alcohol, and finally dried and weighed. The 

 test was purposely made very severe to guard against any 

 possible errors. Removal of zinc from a sheet does not require 

 as much as ten minutes. No attempt was made to keep the 

 temperatures exact by a thermostat, because such refinements 

 are unnecessary in the actual tests. Fifteen-centimeter squares 

 were used. The following results were obtained. 



Table V. — Effect of temperature on solution velocity of iron base. 



strength 

 of acid. 



Temper- 

 ature. 



Loss in 

 weight. 



Loss. 



Calculated 



to ounces 



per square | 



foot. 



Density. 



°C. 



Grams. 



Per cent. 





1.098 



30 



0. 0339 



0.03 



0.005 



1.098 



45 



0.0494 



0.05 



0.007 



1.098 



60 



0. 0921 



0.09 



0.013 



1.098 



80. 



1.3256 



1.26 



0.193 



1.098 



100 



6.1648 



5.93 



0.897 



The temperature of the acid may run up to 60° without 

 causing any appreciable error, but since there is no reason for 



