NOYES AND COOLIDGE. 



ELECTRICAL CONDUCTIVITY. 



213 



XIV. Change of the Conductivity with the Temperature. 



In order 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 eurve 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 drawn 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 

 somewhat striking conclusion that throughout this wide range of temper- 

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



SOD/UM CmlO/R/DE". 



/SOO 



//oo 

 /ooo 



■900 

 GOO 

 7O0 

 600 

 SOO 

 400 

 s3C0 

 SOO 

 /OO 



o 



■40 



SO 



/SO 



/60 c"0O 



Figure 10. 



S40 



sso 



320 



-360 



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 : (A ), = (A ) 18 + a (t — 18). 

 The value (3.34) adopted for a in the case of the sodium chloride \v:is 



