300 



MR. W. R. BOUSFIELD AND DR. T. M. LOWRY ON THE ELECTRICAL 



addition to these definite sources of error the whole operation of measuring the 

 conductivity becomes troublesome when the temperature is raised, and it is therefore 

 not possible to work with the same exactitude as at lower temperatures, at which 

 the distraction and haste arising from temperature adjustment is absent. 



In dilute solutions, for which the temperature coefficient K~ l d,K/dt is about 2 per 

 cent., an error of 0'05 C. in the temperature produces an error of O'l per cent, in 

 the conductivity, but in the concentrated solutions the temperature coefficients 

 are enormously greater. The conductivity of a 50-per cent, solution instead of 

 increasing in the ratio of 7 : 2 between C. and 100 C. actually increases 5 -fold 

 between C. and 18 C., and 80-fold between C. and 100 C. For this reason we 

 are unable to claim for our individual measurements at the higher temperatures an 

 accuracy greater than about 1 part in 100, though the error on a series of measure- 

 ments may be considerably less. 



The total change of conductivity due to the fouling of the solutions heated and 

 cooled in glass vessels amounted in two instances to as much as 1'6 per cent., but the 

 greater part of this is eliminated by our method of correction, and the residual error 

 can scarcely amount to more than 0'5 per cent., since the total change in either the 

 ascending or the descending series cannot have differed much from the half- value, 

 0'8 per cent., that was taken as the basis of our calculations. When using platinum 

 vessels this source of error was eliminated, but the results obtained were so similar in 

 their general character to those obtained when using glass vessels, that we did not con- 

 sider it necessary to repeat all our observations in order to secure the increase of accuracy 

 that might have resulted from the removal of only one of the sources of error. 



TABLE XV. Influence of Temperature on Conductivity. 



NOTE. The values for K O , 18 , K M , and K IOO which are enclosed in brackets are derived from conduc- 

 tivity-temperature observations in vessels that had not been independently calibrated ; values of *c 18 were 

 taken from the isothermal observations recorded in Table XII., the concentration of the solutions being 

 deduced from their densities at 18 C. ; the values of % "so, and K JO O were then calculated from the 

 ratios KO, KSO, KIOO tabulated above. 



