'CONDUCTIVITY OF MIXTURES OF ELECTROLYTES McIXTOSH. 121 



solutions containing sodium chloride and hydrochloric acid, 

 electrolytes whose ionic velocities differ from one another much 

 more than those of sodium and potassium chlorides. 



The expression for the conductivity of a mixture of equal 

 volumes of solutions of two electrolytes 1 and 2, which contain 

 TI I and 7?. 2 gramme-equivalents per unit of volume respectively, 

 the ionisation coefficients of which, in the mixture, are a l and 2 , 

 the molecular conductivities of which at infinite dilution are 

 pool and |Ua>2, and which so change in volume on mixing that the 

 ratio of the volume of the mixture to the sum of the volumes 

 of the constituent solutions is p, is 



1 fa } 



~ 2~p\ l Ui '" col+G2 n2 '"<*) 



In order to calculate the conductivity of such a mixture 

 therefore, the seven quantities in this expression must be known. 

 The ionisation co-efficients a l and a 2 are determined by the 

 graphical process referred to above, from series of observations 

 of the conductivities of simple solutions of the constituent 

 electrolytes. The conductivities at infinite dilution are deter- 

 mined by similar observations with very dilute solutions. The 

 concentrations may be determined by analysis, and the quantity 

 p by density measurements. 



I intended at the outset to determine all these quantities 

 myself, in order that the data of calculation might apply to 

 exactly the same electrolytes. But owing to the fact that the 

 electrolytic cell, to be used in the determination of conductivities 

 at infinite dilution, although ordered months ago, did not arrive 

 in time, I am compelled to use Kohlrausch's values of the con- 

 ductivities at infinite dilution for the electrolytes examined. 



Determination of Conductivities. 



Kohlrausch's well-known method with the telephone and 

 alternating current was used. The apparatus- was supplied by 

 Queen & Co., of Philadelphia, and consisted of a German silver 



