Constants of Pure Ice, tyc, at Low Temperatures. 321 





Mean 





Temperature 



galvanometer 





IIS yJLcL L1I1 Uili 



degrees. 



Hpflppfvion in 



UCUCtHvli ILL 



THp1pr»fvrip 



centimetres. 



constant. Observations. 



-1242 



20-8 



18-1 



-1192 



1-77 



21-8 Charging volts 1'434. 



-1130 



22 



27-1 



—110-2 



2-5 



30-7 



-106-5 



37 



45-8 



-98-8 



5-05 



62-5 



-92-3 



5-8 



717 



-91-7 



6-65 



82-5 



-87-8 



8-2 



1015 



-83-7 



8-59 



105-0 



-80-8 



8-7 



107-5 



-76-4 



8-83 



109-0 



-71-5 



8-85 



109-2 



-69-0 



8-78 



108-5 



-65-6 



8-7 



109-2 



-61-0 



6-62 



106-8 



-57-7 



8-53 



105-5 



-53-9 



8-45 



104-5 



-50-3 



8-33 



103-4 



-46-2 



8-28 



102-4 



-40-7 



8-18 



lOl'O 



Beyond this last temperature ( — 40*7) the observations are not 

 of mnch value. Sensible conductivity had begun to make its appear- 

 ance, and the measurements no longer gave the true dielectric 

 constant. 



These results are plotted in a second curve in fig. 1, marked 

 distilled water. It is clear that there is in this case a well marked 

 maximum value for the dielectric constant at about — 65°, and that 

 above that temperature the dielectric constant falls again. We have 

 already pointed out that in the case of the ice from ordinary dis- 

 tilled water, a very rapid increase of electric conductivity takes 

 place at or about —90°, and the temperature somewhat precedes 

 the temperature at which the dielectric constant is a maximum for 

 the ice. Other observers who have studied the variation of the 

 dielectric constant of water at temperatures above zero centigrade, 

 agree that beyond a certain temperature the dielectric constant 

 decreases with rise of temperature. Thus C. B. Thwing (* Zeit- 

 schrift fur Physikalische Chemie,' vol. 14, 1894, p. 296) gives the 

 following values for the dielectric constant for water using a rapidly 

 oscillating electromotive force : — 



