170 



the licnl coiKliictlxil}" ol" st'V('i-aI metals a1 KJO . Ilis 

 rt'sulls iiulicatc thai in sonic ol' tlicni llic conduclivity is 

 lowiT at low tlian at lii*>Ii temperatures while in others it is 

 liiglier. 



According- to Dickinson, Harper and ( )sl)orn (1914), the 

 heat of fusion of ice is 79.68 calories. 



It is to l)e noticed that the heat of fusion decreases by 

 0.59 calories for every degree of lowering of the fi-eeziiig 

 point. 



Barnes aud Vipond (1909) found that the heat of evapo- 

 ration of ice varies from about 600 calories in rapid evapo- 

 ration to about 700 in slow evaporation. It is not the sum 

 of the heat of fusion of ice (79 cal.) and of the heat of 

 vaporisation of water (598 cal.), but it tends, in rapid 

 evaporation, to become identical with the latter. This 

 renders probable the assumption that ice evaporates with- 

 out passing through the liquid phase, the molecules escap- 

 ing from the ice in the state of a polymeric vapor. 



According to Washburn (1925) and others, the vapor 

 pressure of ice varies from 0° to - 90° as follows : 



The coefficient of linear expansion of ice, as determined 

 by Petterson (1893) is 0.000053 between -2° and -10°. 

 The coefficient of cubical expansion is 0.0001620 according 

 to Nichols (1899). 



4. Electrical Properties. It is known that ice is a good 

 insulator; its specific resistance at 0° is given by Johnson 

 (1912) as 0.367 X 10\ That of distilled water at the same 

 temperature is 0.5 X 10'". 



We mentioned above that the difference in the electric 

 resistance of ice and water has been used by Moran (1935) 

 for the determination of the eutectic point of the muscle. 



The specific inductive capacity of ice at - 5° w^as found 

 by Thwing (1894) to be 2.85 (wave-length of measuring 



