44 



CASSEL, ELECTROLYTICALLY DEPOSITED METALS. 



Metal. 



Solution in tube. 



Solution in vessel. 



Galvanom. 



Mg 



MgSO, 



H2SO4 



+ 



Zn 



ZnSO, 



- 



+ 



Ni 



NiSO^ 



» 



+ 



Fe 



FeSOj 



* 



+ 



AI 



AljSSO^ 



= 



+ 



Cu 



CUSO4 



» 



— 



Ag 



Ag^SO, 



- 



— 



Zn 



ZnCij 



HCl 



+ 



Sn 



SnCIa 



» 



+ 



Pb 



PbClj 



» 



+ 



Bi 



BiClj 



s 



— 



Sb 



SbClj 



» 



— 



Zn 



Zn2N03 



HN03 



+ 



Pb 



Pb2N03 



3 



+ 



Ag 



AgNOj 



- 



— 



Hg 



Hg2N03 



» 



— 



Fe 



Fe^GNOj 



» 



+ 



The relative position of the metals according to this expe- 

 riment is indicated by the following table: 



Mg, AI, Zn, Fe, Ni, Co, Pb, Sn, H, Cu, Hg, Bi, Sb, Ag. 



This series is of course dependent on the electronegative part 

 of the salt, but is correct Avhen the unorganic acids referred to 

 are used. 



With the exeption of Mg (and Al), these metals can be 

 deposited from aqueous solutions, and if deposited secundary, they 

 are all obtained under the same conditions, in regard to tempe- 

 rature. density of current etc. But if deposited from a Solution, 

 ■\vhich only contains one salt, whose electronegative part is a 

 strong unorganic acid, the above named conditions will vary with 

 each of the two classes referred to. 



In such a case fiee acid will always be present, and hydrogen 

 will be evolved, unless the metal in the Solution can be sub- 

 stituted. This liberation of hydrogen is however to be prevented: 

 In the first class by reducing the amount of deposited hydrogen in 



