Mixtures of Electrolytes having a common Ion. 511 



of two electrolytes having a common ion, the data necessary 

 for the calculation of the conductivity of a solution containing 

 both electrolytes, according to the dissociation theory of 

 electrolytic conduction ; and in order to test this theory he 

 calculated the conductivities of a series of mixtures of solu- 

 tions of sodium chloride and potassium chloride, which had 

 been measured by Bender. He found that for dilute solutions 

 his calculations agreed with Bender's observations within the 

 limits of experimental error ; but that as the strength of the 

 solutions increased the differences became larger, until with 

 a mixture of solutions containing each four gramme-molecules 

 per litre of salt (the strongest solutions with which Bender 

 worked) a difference of 3'6 per cent, was found. The method 

 of calculation assumed that the ionic velocities of the con- 

 stituent electrolytes were not changed by the mixing ; and 

 Prof. MacGregor attributed the differences between the calcu- 

 lated and observed values to the change which, as he pointed 

 out, would probably be produced in these velocities by 

 mixture. 



At his suggestion I have made the observations and calcu- 

 lations described in this paper with the object of determining 

 (1) what the differences between the observed and calculated 

 values are, in the case of mixtures of sodium and potassium 

 chloride solutions of greater strength than those examined 

 by Bender ; and (2) how the calculated and observed values 

 are related in the case of solutions containing sodium chlo- 

 ride and hydrochloric acid — electrolytes whose ionic velocities 

 differ from one another much more than those of sodium and 

 potassium chlorides. 



Preparation of Solutions and Determination 

 of Conductivities. 



The paper of which this is an abstract contains a full 

 statement of the experimental methods employed and the 

 precautions taken to secure accuracy. It will be sufficient 

 here to make a general statement merely. 



The salts and acid used were purchased as chemically pure, 

 and the former re-purified by crystallization. They were 

 found by the usual tests to be free from probable impurities. 

 The water was doubly distilled and was also tested. 



Simple solutions of salt or acid having been prepared 

 their concentration w r as determined by volumetric analysis 

 the pipettes and burettes used having been tested by weighing 

 the water they delivered. The volumetric analyses were 

 found to be accurate to 0*1 per cent, when applied to solu- 

 tions specially prepared by the mixture of exactly determined 

 quantities of salt and w T ater. 



