34:6 Prof. J. Traube on the 



those of Richards, and we also agree in thinking that this 

 way of regarding the electrical processes leads much further 

 than the application of the electron theory to electrolytic 

 processes, and especially as regards the conception of elec- 

 trolytic solution pressure. While fully acknowledging the 

 additions due to Mr. Eichards in this respect, I regret that 

 my earlier remarks in this connexion should have been over- 

 looked by him. I have at a much earlier date * established a 

 connexion between the solution pressure of a metal and the 

 difference in the affinity of the solvents for the metal and the 

 affinity of the metal for itself ; and I have even repeatedly 

 pointed out the very remarkable fact — which had not as yet 

 been noticed by Richards — that the atomic contraction of 

 potassium, sodium, silver, Sfc. ions in water is the same, and is 

 independent of the nature of the ion, and that this proposition 

 is strikingly analogous to Faraday s electrolytic law f. it is 

 to be hoped, now that Richards also expresses similar views, 

 that my former views will receive greater attention. 



(b) The Co-volumes (the quantities v — b). 



Not less significant are the conclusions to which we are 

 led by a discussion of those volumes which we denote as 

 co-volumes. 



Since at ordinary temperatures the intrinsic pressure is in 

 most cases not very different for different liquids, the molecular 

 <;o-volume is also in general so nearly constant that frequently 

 it may be used to determine the molecular weight as well as 

 the approximate degree of association. Especially is this the 

 ■case for substances soluble in water without ionization. The 

 molecular volume in solution, or the solution volume% of a 

 dissolved substance is also equal to a sum of atomic volumes, 

 increased by a co-volume, which in the case considered, owing 

 to the contraction which takes place in water, is considerably 

 less than for the undissolved substances, but wliich for all 

 substances not undergoing ionization ivas found to be approxi- 

 mately 12'4 ex. per gramme-molecule as determined by Kopp's 

 method. 



* J. Traube, Ann. Phys. Bd. lxii. p. 505 (1897) ; and Richards, Zeitschr. 

 Physik. Chem. Bd. xl. pp. 179-181. 



| J. Traube, " Raum der Atome," Ahrens Sctmml. Chem. und Chem.- 

 Techn. Vortr. Bd. iv. p. 70 (1899), and Ann. d. Phys. Bd. lxii. p. 505 

 (1897). 



} Cf. J. Traube, F. W. Ahrens Samml. Chem. u. Chem. Tech. Vortr. 

 1899, I. c. 



