Miscellanies. 373 



The mixtures of acid and water which he employed, were, in order. 



Quantity of acid in 100 parts 

 of the mixture by weight. 



- - - - - 30.20 



25.64 



29.85 



- 35.28 



- - - 43.25 



G4.20 



In making the experiments, care was taken that the initial tempe- 

 rature of the dilute acids were the same, and that the same surface of 

 zinc was at each time exposed to it. The same quantity of gas was 

 disengaged by the different mixtures, in times as follows : 



The maximmn of effect on the zinc of commerce was generally at- 

 tained in ten minutes, while in the pure zinc, it required several hours, 

 especially in a very weak acid. In No. 6, the action was most rapid, 

 at the commencement, with both kinds of zinc. 



It appears that the mixture No. 3, is the acid which produces the 

 greatest quantity of gas in a given time with the zinc of commerce, 

 viz. that which consists of 30 parts of sulphuric acid, and 60 of water. 



The great difference thus manifest in the two kinds of zinc, is not 

 owing, as Professor De La Rive ascertained, to a difference in sp. gr., 

 for in this they were precisely equal. It appears therefore to be oc- 

 casioned by foreign mixture, and to ascertain this, he added to a por- 

 tion of distilled zinc in fusion, one ninth of its weight of iron filings, 

 and he did the same with tin, lead, and copper filings, and of them he 

 cast four cylinders, and obtained with them the following results. 



Dist. Tin Lead Copper Iron Zinc of 



Acid No. 1. \ Zinc. Zinc. Zinc. Zinc. Zinc. Com. 



temp. 10° cent. ( 3' 27" 0' 24" 0' 12' 0' 4" to 6" 0' 4' 0' 4' 



Acid No. 2. < ^, ^Q„ Q, j2„ Q, g„ Q, g„ Q, 3„ Q, 3„ 



temp. 10° cent. ( 



Acid No. 3. ( Q, ^Q„ Q, j2', O' 10" 0' 3 " to 4" 0' 2" to 1 ' 0' 2 to 1" 



temp. 10° cent. ( 



Cylinders of these different kinds of Zinc, being left at rest in No. 

 6, until the action ceased, the pure zinc alone gave a perfectly limpid 



Vol. XIX.—No. 2. 48 



