II.—On THE CALCULATION OF THE CONDUCTIVITY OF MIx- 
TURES OF ELECTROLYTES HAVING A Common Jon. 
— By Dovuerias McInrosn, Physical Laboratory, 
Dalhousie College, Halifux, N. 8. 
(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 to 
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 caleniees 
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 ease 
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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