182 



The Philippine Journal of Science 



1916 



lead or other impurity in the coating. The solution is reduced 

 and titrated with 0.1 N potassium permanganate solution to 

 determine the iron dissolved. The amount of iron found is sub- 

 tracted from the weight of coating dissolved by the acid. The 

 rest may be taken as zinc without appreciable inaccuracy. 



Results obtained with new sheets of galvanized iron were 

 as follows: 



Table III. — Amount of zinc spelter on modem galvanized sheets. 



[Flat sheet.] 



Tracing 

 No. 



Sample. 





Weight of coating 

 per— 



Brand. 



No. 



Gauge. 



Square 

 deci- 

 meter. 



Square 

 foot. 











Grams. 



Ounces. 



1 



A 



1 



24 



5.58 



1.83 



2 



A 



2 



23 



6.38 



2.09 



3 



A 



3 



23 



4.94 



1.62 



4 



A 



4 



23 



4.58 



1.60 



5 



B 



1 



24 



4.73 



1.65 



6 



B 



2 



23 



5.46 



1.79 



. 7 



B 



3 



21 



4.94 



1.62 



8 



C 



1 



20 



5.83 



1.91 



9 



C 



2 



24 



4.61 



1.51 



10 



C 



3 



21 



4.70 



1.54 



11 



C 



4 



23 



4.88 



1.60 



12 



D 



1 



25 



4.09 



1.34 



13 



D 



2 



25 



3.76 



1.27 



14 



D 



3 



22 



4.34 



1.42 



15 



E 



1 



23 



3.75 



1.23 



16 



E 



2 



21 



4.76 



1.56 



17 



F 



1 



23 



3.60 



1.18 



18 



G 



1 



22 



7.56 



2.47 



19 



G 



2 



22 



6.72 



2.20 



20 



G 



3 



22 



6.56 



2.15 



21 



G 



4 



22 



6.80 



2.23 



22 



H 



1 



22 



3.43 



1.12 



23 



H 



2 



22 



4.27 



1.40 



24 



H 



3 



22 



4.88 



1.60 



25 



I 



1 



22 



6.56 



2.15 



26 



J 



1 



24 



4.48 



1.50 



27 



J 



2 



26 



4.88 



1.40 



The data in the foregoing tables show that, with two ex- 

 ceptions, even the exposed portions of the old sheets had a 

 heavier coating after thirty years of service than did the modern, 

 unused sheets. The least amount of coating recorded for un- 

 exposed portions of old sheets was higher than the greatest 

 determined for the new. The greater amount of zinc on the 

 old as compared with the modern galvanized sheets doubtless 



