at the Contact of Solids and Gases. 11 



sulphuretted hydrogen the carbon continually approached 

 nearer to the positive end of the tension-series ; there were 

 observed, namely, for Zn | C, H 2 S : — 



At the commencement . . . 1*29 

 After the second saturation . . 1*13 

 After the third „ . . 1*04 



After the fourth „ . . 1-02 



Thus, with the saturation of the solution, the electromotive 

 force approached towards a limiting value which is to be set 

 down as about 



Zn | C,H 2 S=1-02D. 

 so that 



C,H 2 S | C becomes =0-29 D. 



The electromotive forces which were called forth at the pal- 

 ladium by hydrogen, sulphuretted hydrogen, carbonic oxide, 

 and ethylene show, in fact, again a similar proportionality, as 

 I had previously conjectured for all the metals. In the fol- 

 lowing Table I place side by side the values before found for 

 platinum and those now found for palladium, and calculate 

 from the forces observed at platinum those to be expected at 

 palladium, by multiplying the former with the ratio 



Pd | Pd, H : Pt | Pt, H=0-59 : 0-81 = 0:73. 





Pt. 



Pd. 



Pd. 





Found. 



Found. 



Calculated. 



H . . 



. 0-81 



0-59 



0-59 



H 2 S 



. 0-69 



0-42 



0-50 



CO . . 



. 0-28 



0-23 



0-20 



N 2 H 4 . 



. 0-06 



0-05 



0-04 



Metal . 



. 











For the retort-carbon, on the contrary, nothing similar is to 

 be observed ; its state was in general changed only under the 

 influence of greater solubility of the gases or the electric polari- 

 zation. Besides we have no longer any right to designate the 

 factor 0*73 as the coefficient of condensation for palladium, 

 since we know that palladium condenses hydrogen much more 

 strongly than platinum does. 



From the results obtained the following is now evident : — 

 Platinum, palladium, and carbon behave to chlorine exactly 

 alike, so much so that the numerical values found for the 

 electromotive forces Zn | Pt, CI; Zn | Pd, CI; Zn | C, CI 

 stand very near to one another; they amount to 2*08, 2*04, 

 1*97 D respectively. The values which were obtained on the 

 electrolytic evolution of chlorine are here left out of considera- 

 tion, because the attack which therein took place on the elec- 



