ÖFVERSIGT AF K. VETENSK.-AKAD. FÖRHANDLINGAR 18 94, N:0 2. 45 



proportion to the deposited metal, and in the second class by 

 favouring the secondary processes as much as possible. 



It is evident that the two classes are to be treated in an 

 aithogether difterent manner, when deposited out of the solutions 

 referred to, and the following account will show, that the re- 

 sults obtained, in practical operations prove this statement. The 

 handbooks from which these statements are taken, do not and 

 can not claim to be scientific literature, but are reliable by 

 reason of the fact, that their receipes are founded on direct prac- 

 tical experiments. 



As we have mentioned, there are three difFerent circura- 

 stances, which are to be taken in consideration, viz: l:o) the 

 density of current, 2:o) the temperatnre, 0:0) the condition of 

 the electrolyte. 



I. Density of current. 



The first class of metals, which embraces raetals more posi- 

 tive than hydrogen, can be represented by zinc. If deposited 

 from a Solution of f. inst. their sulphates, they generaiiy require 

 a very high density of current. Kiliani^) found, while electro- 

 lysing a concentrated, neutral Solution of sulphate of zinc, that 

 with increased density of current the metal obtained was better, 

 while the amount of hydrogen evolved in proportion to the depo- 

 sited metal decreased. In one of his experiments he obtained 

 the follwoino; results: 



Ampere per m ^. 



Hydrogen evo 



Ived 



in 



The condition of 





c. c. 



per 1.5 



gl'- 



Zn. 



the deposite: 



7 





2.40 







very spoungey 



18 





2.27 







d:o 



38 





0.56 







d:o 



158 





0.43 







1 somewhat firmer, 



\ spoungey on the edges. 



316 





0.33 







f the metal can still 

 \ be rubbed off 



1,843 





— 







verv firm, white and brig 



19,181 





— 







d:o d:o 



') KiLANi, Berg- u. Hüttenztg. 1883, s. 251. 



