the Conductivity of Mixtures of Electrolytes, 



217 



volumes before the mixture were v x f and v 2 respectively, 

 which contained rt\ and n 2 gramme-molecules of ihe electro- 

 lytes per unit of volume, whose combined volume after 

 mixture is p{vi+v 2 ), whose coefficients of ionisation after 

 mixture are a, and a 2 , and whose specific molecular con- 

 ductivities at infinite dilution under the circumstances in 

 which they exist in the mixture are ft Ml and /-i« 2 , is given by 

 the expression 



* = pW + W) t^ 1 ^ 061 + a 2%^V» a ) • 

 Since in any case in which isohydric solutions are mixed 

 without change of volume, n v v/, n 2 , v 2 are known, a x and oU 2 

 readily determinable, and p equal to unity, the specific con- 

 ductivity can be calculated provided we assume that /tt Wl and 

 fi (B2 have the same values for solutions in a mixture as for 

 simple solutions. In the case in which equal volumes of the 

 constituents are mixed without change of volume, the specific 

 conductivity of the mixture becomes the mean of the specific 

 conductivities of the constituent solutions. 



Arrhenius has subjected the above result 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 shown thereby to be 

 isohydric among one another, he calculated the concentra- 

 tions of the ions in the various solutions by the aid of data 

 due to Ostwald. The following table gives the result, the 

 numbers specifying the concentration of dissociated hydrogen 

 (in mgr. per litre) in the constituent solutions, and those in 

 each row applying to solutions found as above to be isohydric 

 with one another : — 



HC1. 



(0OOH) 2 . 



C 4 H 6 6 . 



HCOOH. 



CH3COOH. 



151-5 



152-6 









423 



35-1 









22-03 



21--37 



19-07 







•4-48 



4-09 



417 



4-42 



3-96 



1-33 



1-24 



1-25 



1-44 



i-33 . '...; 



0-379 , 



: 0-397r 



0-381 



...... 



0-402 



