42 CASSEL, ELECTROLYTICALLY DEPOSITED METALS. 



FeSO, 135 gr. 



H4NCI 100 gr. 



HoO 1,000 gr.i) 



and the foUowing is clainied to be a good nikel Solution. 



NiCl2 500 gr. 



H4NCI 500 gr. 



H2O 1,200 gr.2) 



New, if P^eSO^ or NiCl2 be elektrolysed alone the nietals^ 

 will be more or less dentritic and can not be polished. When 

 the conductivity of H^NCl is greater than of both NiCL^ and 

 FeSO^ and when no hydrogen is evolved during the process, 

 it is evident, that the main part of the deposited rnetals is the 

 result of" a chemical reduction by ammonium. In the same 

 manner it is easy to explain the necessity of adding any alkaline- 

 salt prescribed by authors on this subject. 



Tt is, however, not only the alkaline salts which can be used 

 for this purpose; it is only necessary that the salt in question 

 by decomposition gives a cation, which is more positive and has a 

 greater conductivity than the metal, that is to be deposited. Thus, 

 if zincsulphate be electrolysed with an ordinary density of current 

 and by a temperature of about 15' C. the metal is spoungey. 

 But if a concentrated Solution of the sulphates of K, Na, Am 

 or AI is added the zinc deposite becomes firm and hard.^) 

 I have found, that sulphate of magnesia has not this etfect, and 

 the reason is that this salt has as greater conduction resistance, 

 than sulphate of zinc. 



By reason of the fact, that secondary processes very often 

 regulate the results of the electrolytical deposition of metals I 

 have found reason to divide the metals in two classes: the first 

 class embraces metals more positive than hydrogen. the second 

 class comprises those less positive. The reason why the metals 



') Langbein, Galvanische Metallniederschläge 1886, s. 227. 



2) » . > > s. 114. 



3) Hermann, D R. P. N:r 24,682, 24 April 1883; E. Placet et J. Bonnet, 

 Svenska patentet N;r 4257. 



