J. Tl. Reedy — Anodic Potentials of Silver. 



285 



of potential used — so that the curve lies wholly above the 

 horizontal axis. For non-reversible electrodes, as Ostwald* 

 has pointed out, this method gives definite values for reaction 

 potentials only when a product of the reaction is insoluble — 

 that is, a precipitate or a gas. When the products are soluble, 

 the current does not appear abruptly; the slight residual cur- 



Fig. 2. 



30 



20 



10 



<0 



c 

 o 



> 



Q 



* 



-JO 



3 

 O 



■20 



-30 





































o*j 





















<o 1 



*7 









o 1 













J 









o 1 











< 



°7 



;/ 









d 





























/ 















































































































200 300 .400 SOO .600 



Potential in Volts > 



.700 



Fig. 2. Eeaction potentials of silver with 01 molar KC1 and 0-5 molar 

 H2SO4. 



rent (the " Reststrom ") merges into a much larger current 

 (that is, " current of constant polarization ") with a gradual bend, 

 owing to such influences as diffusion, stirring and'thelike. In 

 the present^ investigation this was notably the case in the cur- 

 rent potential curves obtained for silver anodes in solutions 

 containing such anions as SO/', NO,', etc.; or in general, those 

 which form simple soluble silver salts. In such cases the tan- 

 gent to the graph was drawn at the point of greatest curva- 

 * Ostwald-Luther, "Messungen," 1910, p. 455. 



