ÖFVERSIGT AF K. VETENSK.-AKAD. FÖRHANDLINGAR 18 94, N:0 2. 41 



•cularly ■ palpable: if Mater acidutated with sulphuric acid is 

 electrolysed, hydrogen is received in a quantity fuliy equivalent 

 to the current; but it" cristals of cupric sulphate are added, the 

 gas ceases immediately to evolve and copper is now deposited in 

 a quantity equivalent with the current.') Now when the conduc- 

 tivity of H0SO4 is about ten tiraes as great as that of CUSO4, 

 there is no plausible reason why, by merely adding the salt, the 

 current should cease to be transmitted by the acid iri order to 

 be transferred exclusively by the salt. The fact is, that by the 

 presence of this acid the conduction capacity of CuSO^ is still 

 further depriraated, so that it is safe to assert, that över 90 % 

 •of the current are transmitted by the ion H; and when this gas 

 •does not appear in free form it must have substituted Cu from 

 the Solution. If the density of the current exeeds a limit, fixed 

 by the temperature and the concentration of the Solution, '■^j the 

 H-ions are deposited so rapidly after each other that the difFussion 

 of the liquid has not sufficient time to supply the cathode with 

 fresh molecules of CuSO^: Hydrogen is evolved and the weight 

 of the deposited copper is no longer equivalent to the current. 



The gas referred to appears earlier and with less density 

 of current if the diffussion of the liquid is diminished as by 

 lowering the temperature ^) or by placing the electrodes horisontal 

 with the cathode above the anode.*) 



The hand-books on this subject give a great number of 

 •different recipes for the electro-deposition of those metals, which 

 «annot be obtained from an acidulated Solution. According to 

 these prescriptions alkaline salts are generally added to the electro- 

 lyte in great quantities. Thus, if iron is to be deposited, the 

 foUowing Solution may be used: 



') The experiment must be made with a density of current, not exceding 50 

 ampere per m^ and by a temperature not lower than 15'^ C. 



^) VoLKMAR, »Betrieb der Galvanoplastik mit dynamoelektrischen Maschinen, zu 

 Zwecken der Graphischen Kunst» 1888, s. 38, samt Gore, Electrolytic Sepa- 

 ration of metals s. 105. 



^) Phanhauser, Metallplätirung und Galvanoplastik 1890, s. 140, samt Lang- 

 bein, Galvanische Metallniederschläge 1886, s. 104. 



^) Smee, Phil. Mag. 25, s. 437, 1844. 



