378 Profs. J. Dewar and J. A. Fleming. On the Dielectric 



-200° -150" -100" -50" 3 



TiG-. 1. — Curves showiag the variation in Dielectric Constant with Temperature of 

 various Oxides and Hydrates. 



It is possible, however, that in this case the conductivity of 

 the yet insnlated particles of oxide may account for the 

 result. 



(v) The effect of the solvent or menstruum upon the dielectric 

 constant is also exceedingly marked. Thus the oxide of 

 copper suspended in ice has a dielectric constant of about 

 150 at —185°, the oxide of lead suspended in ice has a value 

 of about 80 at the same temperature. If, however, the oxide 

 of copper is dissolved in ammonia and frozen, the dielectric 

 constant of this at —185° falls to 2*2, whereas if the oxide of 

 lead is dissolved in 5 per cent, solution of caustic potash and 

 frozen, the dielectric constant rises to 170 at the temperature 

 ,of liquid air. 



