II. ON THE CALCULATION OF THE CONDUCTIVITY OF MIX- 

 TURES OF ELECTROLYTES HAVING A COMMON ION, 

 BY DOUGLAS MC!NTOSH, Physical Laboratory^ 

 Dalhousie College, Halifax, N. S. 



(Received April 6th, 1896.) 



In a paper read before this Institute some months ago, Prof.. 

 MacGregor * shewed how to obtain, by a graphical process, 

 from observations of the electrical conductivity of a sufficient, 

 number of simple solutions of two electrolytes having a com- 

 mon ion, the data necessary for the calculation of the conduc- 

 tivity of a solution containing both electrolytes, according ta 

 the dissociation theory of electrolytic conduction ; and in order 

 to test this theory, he calculated the conductivities of a series 

 of mixtures of solutions of sodium chloride and potassium 

 chloride, which had been measured by Bender. He found that, 

 for dilute solutions his calculations agreed with Bender's obser- 

 vations within the limits of experimental error ; but that, as the 

 strength of the solution 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 

 constituent electrolytes, were not changed by the mixing, and 

 Prof. MacGregor attributed the differences between the calculated 

 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 described in 

 this 'paper, with the object of determining (1) what the differ- 

 ences 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 



* Trans. N. S. Institute of Science, Vol. IX, p. 101. 



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