[ Barnes] 



THE PHYSICAL CONSTANTS OF ICE 



9 



Hess, in 1848, found for an interval of temperature l)etweeu — 14° 

 and 0°C. the value 0.533; Person, in 1830, found the value 0.480 be- 

 tween — 78° and 0°C. Between — 20° and 0°C. he also found the value 

 0.504. 



The specific heat of ice near the melting point is of considerable 

 interest. Person concluded from his measurements that this increased 

 rapidly as 0° was approached. In his opinion ice was partially melted 

 near 0°C. and then the specific heat was increased by the' latent heat of 

 fusion. 



A valuable comparative measure of the specific heat of ice at dif- 

 ferent temperatures near the freezing point was made by A. W. Smith 

 in 1903. In his determination of the latent heat of fusion of ice it was 

 necessary for him to gain an accurate knowledge of the mode of varia- 

 tion of the specific heat near the melting temperature. He carried out 

 his measurements between — 1.40° and 0°C. The result of his work is 

 to show no measurable change in the specific heat between the limits of 

 his experiments, contrary to the views of Person. 



Sir James Dewar, in 1905, carried out an interesting series of 

 experiments on the specific heat of various substances at low tempera- 

 tures. The calorimeter employed was a bulb containing liquid air or 

 hydrogen enclosed in an outer bulb also containing the same materials. 

 The heat introduced by the body under investigation vapourized the liquid 

 air and from the amount of air thus collected the heat was estimated. 

 A standard substance was used in every case, such as lead, which was 

 found to have only a small variation of specific heat with temperature. 



