at the Contact of Solids and Gases. 9 



following tension-differences were found : — 



1-97, 1*97, 1-94, 2-01, 



Mean ... Zn | C,C1=0'69D; 



from which it follows that 



C | C,C1 = 0'69D. 



When the chlorine was not brought into the tube from 

 without, but evolved immediately at the carbon electrode by 

 electrolysis of diluted hydrochloric acid, still greater electro- 

 motive forces were obtained — namely, 



2-13, 2-25, 2*18, 



Mean ... Zn | C C i=2'19D. 



With longer-continued polarization Macaluso observed yet 

 higher values. 



That carbon electrodes are strongly polarized by electrolysis 

 in dilute sulphuric acid is already known ; Dufour*, particu- 

 larly, has recently called attention to it. I found the polari- 

 zation for both electrodes together 



2-08, 2-21, 1-96, 2-04, 



Mean ... H | C o = 2'07D. 



After restoration of the connexion with the zinc-cell, there 

 was found for the polarization of the negative electrode — 



0-27, 0-26, 



Mean ... Zn | C H = 0'26D; 



and for the positive — 



2-16, 2*38, 



Mean... Zn | C = 2'27D. 



Further, by direct comparison were found : — the force be- 

 tween pure carbon and carbon polarized with hydrogen — 



1-07, Ml, 



Mean ... C H | C=1"09D; 



and between carbon pure and polarized with oxygen — 



1-07, 1-04, 



Mean ... C | C o = l'05D. 



Hence we should have 



C H I C = 2-14D, 



while 2*07 had been found directly. 



* Bull. Soc. Vaud. [2] xix. p. 63 (1876) ; Wied. Ann. Beiblatter, i. 

 p. 573. 



