2 CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



unsaturated compounds, and it is to this unsaturation that he ascribes dis- 

 sociating power. He also attributes the dissociating power of solvents con- 

 taining nitrogen to the fact that in these compounds nitrogen exists as a 

 triad, while it has the power of becoming pentavalent. He predicted disso- 

 ciating power for compounds containing trivalent nitrogen, including the 

 hydrazines, the amines, the diazo compounds, and liquid hydrocyanic acid; 

 and even for other classes of unsaturated compounds, as the trichlorides of 

 arsenic and phosphorus, the mercaptans, and alkyl sulphides. This prophecy 

 is borne out, to some extent at least, by the later work of Walden. In his 

 last paper Briihl sought rather to connect dissociating power with a high 

 dielectric constant, and with the tautomerizing power of the solvent. 



Ciamician 1 concluded that dissociating power is a function of the chemical 

 properties of the substance, and that those substances which resemble water 

 chemically, as methyl and ethyl alcohols, should have the greatest dissoci- 

 ating power. 



Konowalow, 2 from a study of the conductivity of the compounds which 

 amines form with acids, holds that only those solutions conduct in which 

 there is chemical action between the solvent and the dissolved substance. 



Dutoit and Aston 3 advanced the idea that dissociating power is related to 

 the amount of the polymerization of the solvent. Water and the alcohols, 

 which are good dissociants, also exist as polymerized molecules, as is shown 

 by the surface-tension method of Ramsay and Shields. 4 



For further views on this subject consult the paper by Crompton. 5 



Donnan says : 



In a solution in which the solute is more or less ionized, one might suppose the ions 

 to be surrounded by clusters of solvent molecules which had, so to speak, condensed 

 around them, and opposed an obstacle to their recombination. Now one might suppose 

 this state of things as being caused by some sort of specific attraction between the solvent 

 molecules and electricity, i. e., the electrons or electrical charges which are associated 

 with the ions. Were this the case, one might expect this specific attraction to mani- 

 fest itself in other ways. For example, if electrical nuclei were present in, or were pro- 

 duced by any means in air which was saturated with the vapor of an ionizing liquid, 

 then it would be just possible that the specific attraction referred to above might help 

 to produce condensation of the vapor around these nuclei under suitable conditions, i.e., 

 if the vapor were supersaturated by a sudden adiabatic expansion. If the liquid in 

 question did not act as an ionizing solvent, it would be natural to expect that the condensa- 

 tion just alluded to would only occur when the vapor entered the really unstable (labile) 

 region, or at any rate would only be produced by a much higher degree of supersaturation. 



From his experiments, however, he does not feel warranted in drawing 

 any final conclusion. 



l Ztschr. phys. Chem., 6, 403 (1830). 2 Wied. Ann., 49, 733 (1893). 



3 Compt. rend., 125, 240 (1897). See also Dutoit and Friderich: Bull. Soc. Chim., [3] 



19, 325 (1898). 

 'Ztschr nhys. Chem., 12, 433 (1893). 6 Journ. Chem. Soc., 71, 925 (1897). 



