CONDUCTIVITY OF SODIUM HYDROXIDE IN AQUEOUS SOLUTION. 



303 



subtracting consecutive values of K and dividing by the temperature differences. The 

 curve so plotted was obviously a parabola with axis at right angles to the axis of 

 temperature and vertex at the value of t = 44 approximately. The equation of this 

 parabola WHS of the form 



<lK/dt = a 6(44 <)*, 



which, on integration, gave the conductivity-temperature relation in the form of a 

 simple cubic equation 



The values of the constants worked out at c = 0'0980, = '00321, y = 0*0000000767 ; 

 using these constants, the calculated values shown in the table were obtained. As 

 will be seen, they agree with the observed values within the limits of experimental 

 error. 



TABLE XVII. 



Significant Formula for the Conductivity-Temperature Curves. The cubic formula 

 gave a satisfactory agreement in the case of those curves which exhibit a point 

 of inflexion between C. and 100 C., but was not so satisfactory when applied 

 to curves which are not inflected between these limits. We were, therefore, led to 

 devise a formula which should give expression to the variation with temperature of 

 the three factors of concentration, ionic mobility and ionisation, on which the specific 

 conductivity depends. Of these only one can be directly determined, namely, the 

 concentration, which decreases with rising temperature in the same ratio of the 

 density. 



In arriving at the significant formula we have assumed, in accordance with the 

 considerations advanced in Part VI. of the paper, that the changes of ionic mobility 

 may be expressed by a formula similar to that which represents the influence of 

 temperature on fluidity, an assumption which does not depend on the existence of any 

 direct proportionality between mobility and fluidity. In a similar manner we have 

 assumed that the decay of ionisation may be expressed by a formula similar to that 

 which represents the decrease of specific inductive capacity with rising temperature. 



