105 



the weight of zinc necessary l<> produce 11.2 litres of hydrogen is cal- 

 culated. (11.2 litres of hydrogen weigh one gram). 



The accuracy of the method was tested by .Mr. Kimerline, a soph- 

 omore student in chemistry, who made three determinations each of 

 three metals. The average of the closely agreeing results is as follows: 

 aluminum, 9.02 (theory 9.03); magnesium. 12.08 (theory 12.18); zinc, :!2. ."">."> 

 (theory 32.7). In a class of 70 freshmen who had worked in the lab- 

 oratory only IS hours, and using horn-pan balances, the average of .'!7 

 results picked at random was 31.9. 



The apparatus apparently gives good results even in the hands of in- 

 experienced men. 



