( 418 ) 

 Zn + Hg2 SO4 ;t Ug3 + Zn SO4 



at different temperatures. 



The reaction represented by the above equation takes place in a 

 CLARK-cell when its circuit is closed. 



When the cell is short-circuited by a short, thick wire (whose 

 resistance is practically zero) the constant of the electrical velocity 

 of reaction (see my first communication) at f is 



^' = s- 



where E is the electromotive force of the cell at t° and S2 the 

 specific resistance of the saturated solution of zinc sulphate in the 

 cell at the same temperature. 



According' as the solid substance present is Zn S O4. 7 Hg or 

 Zn S 0,x. 6 Ho 0, we shall find at one and the same temperature, two 

 values for Ki since both E and SI depend on the nature of the 

 solid phase. 



3. Jaeger i) has found that for an element in which the stable 

 solid phase is Zn S O4 . 7 Hg 0, the electromotive force at the tem- 

 perature t° may be represented by: 



Et— 1. 400—0, 00152 (<— 39) — 0, 000007 (<— 39)2 Volts. 



If, however, the solid phase is ZnSO^,. 6 H3O, we have 



E'i — 1. 400 — 0, 00102 (i-39) — 0, 000004 (<— 39)^ Volts. 



I have determined the resistance of the different solutions by 

 raeans of a Kohlrausch dipping-electrode 2) (Taiichelectrode) the 

 resistance capacity of which, at 18°, was determined by a 0.5 N.KCl 

 solution, and controlled by a 0.5 N. Na CI solution at the same 

 temperature. 



Table I contains the values of E^ i2, and K^ for the case that 

 Zn SO4. 7 H2O is present in the element and Table 11, the same 

 quantities for Zn SO4. 6 HgO. 



1) WiEU. Ann. Bd. 63 (1897) 354. 



^) Kohlrausch a. Holboen, Das Leitvermögen der Electrolyte. (Leipzig 1898). 

 p. 18 u. 19. 



