NOYES AND COOLIDGE. 



ELECTRICAL CONDUCTIVITY. 



213 



XIV. Change of the Conductivity with the Temperature. 



In ordei' to show more clearly the effect of temperature on the con- 

 ductivity, the values of Table IX are represented graphically in Figures 

 10 and 11. (The dotted curve for the 0.5 normal sodium chloride solu- 

 tion is based on values extrapolated from 0.1 normal by means of the 

 Kohlrausch linear equation, and it has been drav^^n only to indicate 

 roughly the general character of the curve at a higher concentration.) 



A consideration of these plots and of the data themselves leads to the 

 somewrhat striking conclusion that throughout this wide range of temper- 

 ature of nearly 300°, the conductivity extrapolated for zero concentra- 



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Figure 10. 



tion, and therefore the migration velocity of the ions, increases in the 

 case of sodium chloride at a rate closely proportional to the increase of 

 temperature. In the case of potassium chloride this principle expresses 

 the results without considerable error up to 218°, but at the higher 

 temperatures the conductivity increases somewhat more slowly than it 

 requires. 



To show the extent of the deviations, the conductivity has been ex- 

 pressed by a linear equation of the form: (Aq)^ = (Aq)i8 ■\- a {t^ — I8j. 

 The value (3.34) adopted for a in the case of the sodium chloride was 



