MIXTURES OF ELECTROLYTES MACGREGOR. 103 



i. e., the amount of the common ion which is dissociated per unit 

 of volume, must be the same in both constituent solutions. 



According to the dissociation theory, the specific conductivity 

 of a mixture of two solutions of electrolytes 1 and 2, whose 

 volumes before mixing were v\ and i>' 2 respectively, which 

 contained n l and n 2 gramme-equivalents of the electrolytes per 

 unit of volume, whose combined volume after the mixture is 

 p (v\ -f- T/ 2 ), whose co-efficients of ionisation after mixing are 

 ! and 2, and whose specific molecular conductivities at infinite 

 dilution, under the circumstances in which they exist in the 

 mixture, are juooi and ^002, is given by the expression : 



Since in any case in which isohydric solutions are mixed without 

 change of volume, n^, v\,n 2 and v 2 are known, a l and 2 readily 

 determinable, and p equal to unity, the specific conductivity can 

 be calculated, provided we may assume that ft*>i and ^002 have the 

 same values in the mixture as in simple solutions. In the 

 particular case in which equal volumes of the constituents are 

 mixed without change of volume, the conductivity of the mix- 

 ture becomes obviously the mean of the conductivities of the 

 constituent solutions. 



Arrhenius has subjected the result referred to above to a 

 number of tests. In one he determined by experiment several 

 series of dilute aqueous solutions of different single acids, such 

 that if any two of the members of the same series were mixed 

 in equal volumes, the mixture was found to have a conductivity 

 equal to the mean of the conductivities of the constituents. 

 Regarding the solutions of each series as shewn thereby to be 

 isohydric among one another, he calculated the concentrations of 

 the ions in the various solutions by the aid of Ostwald's obser- 

 vations of the conductivity of acids. The following table gives 

 the result, the numbers specifying the concentration of dissociated 

 hydrogen (in rngr. per litre) in the different solutions, and those 



