2 6 Dr. Bevan Lean on the 



Turning now to the researches of Ostwald and his col- 

 laborateurs on the Electrolytic conductivity of carboxy lie acids 

 other facts are found, which have significance in the present 

 connection. In 1884, Arrhenius advanced the theory that 

 the electrolytic conductivity of acids is proportional to the 

 velocities of their reactions or ' affinities ' as measured by 

 several methods. This proportionality was fully verified by 

 W. Ostwald in 1884-5, an d hence, as electrolytic conduc- 

 tivity can be measured with very great accuracy, a most 

 important method is at hand by means of which to obtain 

 a further insight into the functions of acids. Ostwald 

 especially studied the influence of dilution upon the electro- 

 lytic conductivity of aqueous solutions of acids. He found 

 that all the strong monobasic acids, such as hydrochloric or 

 hydrobromic acids, have nearly the same conductivity, and 

 that this increases 10-12 per cent, on dilution. Kohlraush 

 proved that the conductivities of strong acids reach a 

 maximum at great dilutions and then remain constant, a 



fact which he attributed to the complete dissociation of an 



. + 



acid RiH into the ions Ri and H. With weak monobasic 



acids, however, Ostwald showed that values are obtained, 



which still increase with the utmost dilution ; nevertheless 



he has shown how to calculate from determinations at finite 



dilutions what he has termed the dissociation or affinity 



constant of the acid. 



It has been shown above that the researches of Thomsen 



and Massol upon the heats of neutralisation of acids bring 



out the fact of the strengthening influence which one 



carboxyl exerts upon another. Further evidence of this 



effect is afforded by a consideration of the affinity 



constants of acids. The following table has been drawn up 



to show the relation between the affinity constants of 



the monobasic acids of the acetic series and the dibasic 



acids of the oxalic series. 



