102 On the Degree of Dissociation of Electrolytes at 0°. 



sending a small current through this space seems to effect a 

 change in the qualities of the rarefied gas as a conductor which 

 makes it conduct better. There are certain after-effects in 

 some cases which are strongly similar to the polarization of 

 electrodes observed in the case of liquid electrolysis, and which 

 seem to point to the validity of the view that gaseous con- 

 duction is effected by a similar process. 



The experiments also confirm the opinion of Professor J. J. 

 Thomson that gases, or at least certain gases in a rarefied con- 

 dition, are very good conductors, and they show that the 

 greatest part of the obstacle to conduction through a vacuum- 

 tube is at the electrodes and may be largely removed by 

 heating the kathode to incandescence. 



IV. JSote on the Degree of Dissociation of Electrolytes at 0°. 

 By Meyer Wildermaj*n 3 Ph.D.* 



IN the Philosophical Magazine, February 1896, Mr. Wood 

 published a paper, " The Degree of Dissociation of some 

 Electrolytes at 0°," in which he, by a curve, illustrates certain 

 molecular freezing-point depressions, by some misapprehen- 

 sion attributing them to me. The reader will see from the 

 paper which he cites (Phil. Mag. July 1895) that, contrary 

 to his statement, Arrhenius s generalization finds an excellent 

 confirmation. 



In the interest of the matter I wish to add a few words on 

 the following point. The good agreement between the degree 

 of dissociation as obtained from the freezing-point depressions 

 (at 0°) and from electric conductivity (18° and 25°) has 

 already shown that there can only be a little difference 

 between the degrees of dissociation as obtained from electric 

 conductivity at 0° and at 25°. Mr. Waldcn's investigations 

 (Zeitschr. f. phys. Chem.) on the electric conductivity of acids 

 at different temperatures lead to the same conclusion. What 

 I suggested in my paper was that, as we find some differ- 

 ences between the degrees of dissociation of acetic acid at 

 18° (Kohlrausch) and at 25° (Ostwald), the electric conduc- 

 tivity of salts and acids, &c. should be investigated near to 

 the freezing temperature in order to ascertain the small 

 differences possibly existing. This is of interest because 

 of the importance of Arrhenius's generalization ; but it re- 

 quires accurate work, and must only be carried out on a 

 broad basis, as has been done by Kohlrausch and Ostwald 

 at other temperatures. Mr. Wood does not investigate the 

 * Communicated by the Author. 



