3 oo SCIENCE PROGRESS. 



Isomeric ions of analogous constitution have almost the 

 same velocities. If the weight of an ion be increased by 

 equal increments, the velocity is diminished by amounts 

 which become smaller and smaller. In oeneral a retarding 

 effect is produced on replacing H by CI, Br, I, Me, NH 2 or 

 N0 2 ; or on replacing N by P, As, or Sb ; or S by Se or 

 Te. Retardation also occurs if monamines be converted 

 into diamines, or dicarboxylic acids into monocarboxylic 

 acids, etc. Constitution often exerts a marked influence ; 

 of metameric ions the most symmetrical travels fastest. 

 There can be no question, therefore, of the closeness of the 

 relation which exists between the ionic velocity and the 

 chemical nature of the ion. 



The influence of the nature of the solvent on the con- 

 ductivity has been investigated by Vollmer (117), who uses 

 solutions in water, methyl alcohol and ethyl alcohol. In 

 general the conductivity increases with the dilution, and 

 approaches a limit. If the limiting value for water be 

 taken as 1, in the case of methyl alcohol it is 073, and in 

 the case of ethyl alcohol C34. In very dilute solutions the 

 temperature coefficient of the conductivity is practically 

 the same as that of the viscosity coefficient of the solvent. 

 Ostwald's dilution law does not apply, and the author finds 

 in accord with other observers (see p. 297) that the boiling- 

 point of an alcoholic solution cannot be calculated from the 

 conductivity. Intimately related to these observations are 

 those of Kawalki (118) on the diffusion of salts in alcohol. 

 The diffusion coefficient is not quite constant, but increases 

 with the dilution. The important point, however, is that 

 at any concentration the ratio of the diffusion coefficients in 

 water and alcohol is practically the same as that of the con- 

 ductivities at infinite dilution. The rate of movement of 

 the ions in water is therefore about three times as fast as in 

 alcohol, and the results in the main support the dissociation 

 theory. 



Wildermann (119) shows that the order of the dis- 

 sociation of acetic acid and certain of its derivatives is the 

 same in alcohol as in water, and Campetti (120) finds that 

 the transference numbers of lithium chloride and silver 



