2 M. W. Beetz on the Excitation of Electricity 



wire surrounded by the gas and dipping in the liquid he gra- 

 dually lowered until it was all covered by the latter ; he then 

 obtained precisely the same difference of tension as when one 

 part of the wire was surrounded by the gas and the other by 

 the liquid. This result I accounted for by remarking that, in 

 making the experiment thus, the wire had at first been actu- 

 ally in contact with the gas, and then carried a condensed 

 layer of gas with it into the liquid*. I have further, in the 

 above-mentioned treatises, stated my views upon the follow- 

 ing : — that the amount of the difference of tension between a 

 clean metal and one coated w r ith a gas depends on the degree 

 of such condensation of the gases ; that the condensation is 

 greater or less, according to the metal with which the gas 

 elements have been produced ; and that a singularly high 

 degree of condensation is produced by electrolytic polariza- 

 tion, on account of which the electromotive force of the gases 

 is in this case peculiarly great. The considerable difference 

 of tension produced by the action of even small quantities of 

 hydrogen on platinum I compared to the analogous pheno- 

 menon shown by the position of the amalgams in the ten- 

 sion series. Macaluso has moreover pointed out that far 

 greater electromotive forces can be generated by the long- 

 continued electrolytic evolution of hydrogen, or chlorine, or 

 at platinum or carbon electrodes than by simple contact of 

 the gases with the plates or by gas being evolved at them 

 during a short time; he therefore believed that an active 

 state must be ascribed to the gases separated by electro- 

 lysis, similar to that which is known to us in oxygen f. In 

 truth, as regards hydrogen, the presence of an active modifi- 

 cation, previously assumed by Osann, has been rendered very 

 doubtful by Magnus %. 



While the subject of all the above investigations was the 

 presence of considerable quantities of gas on the metal plates, 

 there has recently been a discussion in detail of the case in 

 which only thin films of gas have formed upon the plates. 

 F. Kohlrausch has subjected these films to a careful consi- 

 deration § ; and Helmholtz || and HerwigH have made the 

 analogy between a layer of liquid connecting two polarized 

 electrodes and a condenser the subject of their investigations. 

 Herein Helmholtz has advocated the view that in the polari- 



* Pogg. Ann. vol. cxxxii. p. 461. 



f Ber. d. k. sacks. Ges. d. Wiss., math.-pliys. CI. 1873, p. 306. 

 % Conf. Wiedemann, Galvanismus, 2nd ed. vol. i. p. 533. 

 , § Gott. Nachr. 1672, No. 23, p. 453. 

 , || Monatsb. d. Berl Ahcid. d. Wiss. 1873, p. 587. 

 11 Wied. Ann. ii. p. 566. 



