156 



Th^ Philippine Journal of Science 



1916 



It is evident that the results obtained by use of hydrochloric 

 acid are accurate. The amount of iron dissolved, in terms of 

 ounces per square foot, is a constant to two decimal places. 

 Analytical results check those obtained by the acid method, and 

 the amount of iron dissolved varies but slightly from that in 

 the lead acetate. That slightly less iron is removed by the lead 

 acetate may be explained by the fact that the acetate does not 

 dissolve all of the zinc-iron alloys. This may also explain 

 why the results of the iron determinations in the acetate 

 solution are not so uniform as those in the acid solution. A 

 square of galvanized iron which had been stripped in lead 

 acetate was washed and then placed in hydrochloric acid for 

 some minutes. On analysis it was found that both iron and 

 zinc had been dissolved from the plate. However, it may be said 

 that while the presence of the zinc is of experimental interest 

 it was not present in sufficient amount seriously to affect the 

 results. 



EFFECTS OF CONCENTRATION AND OF TEMPERATURE 



In using hydrochloric acid for removing zinc from galvanized 

 iron, some attention must be paid to the concentration and 

 temperature. Also it is obvious that an iron sheet should not 

 be left in the acid longer than is necessary to remove the last 

 of the zinc. These factors may be easily controlled, and the 

 allowable range is so large that the test is perhaps the simplest 

 of any yet published. 



In deciding what strength of acid to employ in the work, 

 the most important point is to have an acid that will remove all 

 the zinc and as little iron as possible. Two other factors to be 

 considered are the speed with which the acid dissolves the zinc 

 and the rise in temperature caused by the reaction. Table IV 

 shows the results obtained by using three different concentra- 

 tions. 



Table IV. — Effect of acid concentration." 



No. 



1 

 2 

 8 



Dilu- 

 tion 



acid. 



Den- 

 sity 

 of 

 acid. 



Per 

 cent 

 HCl. 



Vol- 

 ume 

 of 

 acid. 



In- 

 itial 

 tem- 

 pera- 

 ture. 



Final 

 tem- 

 pera- 

 ture. 



Character 

 of reaction. 



Total loss 

 (a). 



Iron dissolved 

 (b). 



b/a. 



Zinc 

 dis- 

 solved. 



Per 900 

 square 

 centi- 

 meters. 



Per 

 sq. 

 foot. 



Per 900 

 square 

 centi- 

 meters. 



Per 



sq. 

 foot. 



conc- 

 1-1- 

 1-3.. 



1.190 

 1.098 

 1.052 



37.58 

 19.55 

 10.55 



c.c. 

 400 

 400 

 400 



°C. 

 30.0 

 30.0 

 33.5 



°C. 

 50.0 

 41.5 

 40.0 



Violent... 

 Medium .. 

 Slow 



Gms. 

 73.3449 

 73.3449 

 71. 1473 



Ozs. 

 2.67 

 2.67 

 2.59 



Gms. 



4.1205 

 3.0217 

 3.0217 



Ozs. 

 0.15 

 0.11 

 0.11 



P.ct. 



5.62 

 4.12 

 4.25 



All. 

 Do. 

 Do. 



■ Each sheet was 16 by 16 centimeters. 



