HYDROGEN IN ELECTROLYTIC ZINC 153 



The results are given in Table 1. 



Deposited from 8 per cent. Zinc Sulphate 



Current Density Current C. C. Hydrogen 



(Amperes Efficiency Apparent per gram 



per sq. ft.) (Per cent.) S. G. Zinc 



10 93 7.2 1.3 



20 68 , 6.1 1.3 



30 45^ 6.6 1.1 



60 173 6.2 2.2 



15 per cent. Zinc Sulphate 



20 89 6.5 0.7 



30 84 6.8 0.4 



60 87 6.5 0.7 



100 84 6.2 0.8 



35 per cent. Zinc Sulphate 



20 95 6.5 0.6 



30 94 5.9 0.8 



60 98 6.5 0.4 



100 95 5.7 0.9 



In order to see whether any of the hydrogen was pumped 

 off during the preliminary exhaustion, the volume of the pyrex 

 tube was carefully determined, and the volume of the air dis- 

 placed by the zinc calculated. The following are the results 

 per gram of zinc. 



Gas pumped off during exhaustion 0.07 c. c. — 13% 



After standing for 24 hours at low pressure 0.05 c. c. — 9% 



On heating to 200° C 0.06 c. c— 11% 



On melting 0.35 c. c— 67% 



Total 0.52 c. c; S. G. of Zinc 6.7 



2. Poor Deposit 



3. Poor Deposit: black surface. 



