354 ON THE CALCULATION OF THE CONDUCTIVITY OF 



constituent simple solutions of the equi-molecular mixtures, as 

 the case may be; (2) their concentrations of ions; (3) the 

 dilutions, in litres per gramme-equivalent, of the respective salts 

 in the regions of the solutions occupied by them, determined by 

 the graphical process referred to above, on the hypothesis that 

 the salts exist separately, (4) the values of the conductivities as 

 measured, and (5) as calculated, and (6) the excess per cent, of 

 the former values over the latter. The concentrations of ions, 

 that is the ionization coefficients divided by the dilutions, and 

 the conductivities, are given in terms of the units before 

 specified. The solutions, the values of whose concentrations are 

 printed in italics, were made up in the cell. 



In the case of the double salt solutions from 1 gr.-eq. per litre 

 down to 0.4, the values of the conductivities are less than they 

 would be if the salts were separated, as judged from the values 

 calculated on that hypothesis. For this range of solutions the 

 signs in the last column are all positive, and the differences are 

 beyond the limits of error, though in. two cases not much beyond. 

 With the first four solutions the excess of the calculated values 

 does not differ much, though the fourth is unexpectedly high. 

 On the first addition of water to the 0.5019 solution, the difference 

 becomes much smaller and continues so as water is added. 

 Moreover, with most of the solutions from 0.5 to 0.37, that is, 

 with the solutions which were diluted in the cell, the conduc- 

 tivity rose after the water had been added and mixed. In these 

 cases the last value observed was taken as the conductivity of 

 the solution. Thus the first measurement of the conductivity of 

 the 4075 solution gives a value 1 per cent, less than the calcu- 

 lated value ; but the last two measurements of the same solution 

 taken half an hour later give a value only 0.6 per cent. less. In 

 the case of the 0.4183 solution, however, no change was noticed. 

 The effect is as if the addition of wacer, and possibly also the 

 stirring of the solution, caused the double salt to undergo rapid 

 dissociation. But it may have been due to the thorough mixture 

 of the original solution and the water added, requiring time. 



In the case of the dilute solutions the differences are within 

 limits of error, although their signs are not entirely satisfactory 



