Ice and its Natural History 



255 



increased in the ratio 98*3 5 2 : 100; but this has been considered 

 unnecessary. 



It will be seen that the surface of the water exposed to 

 the constant pressure, 14,000 kilograms, is roughly propor- 

 tional to the volume of the ice exposed to the influence of the 

 constant quantity of 1*5105 gram, or 0-0258 gram-molecule 

 of chloride of sodium. The proportionality is the closer the 

 greater the surface of the water compressed and the greater 

 the volume of ice which contains the salt. 



In comparing the power of inducing the freezing of water 

 at temperatures below o C, possessed by a given absolute 

 pressure and by a given mass of a particular salt, we see that 

 the following law holds : The surface of the water exposed 



TABLE V. 



to the pressure and the volume of the water which holds 

 the salt in solution are approximately proportional. 



It was shown in my paper 1 on ' Steam and Brines,' that the 

 elevation of the boiling-point of water by pressure, and by 

 dissolved salt, follows the same law : there is the same 

 approximate proportionality between the surface which 

 supports the pressure and the volume which holds the 

 salt. 



Influence of Impurity on the Apparent Latent Heat of Ice. 

 This is illustrated by the numbers in Table I. Thus, at 

 r C., the apparent volume of the block of ice is 991-644 c.c., 



1 'On Steam and Brines,' by J. V. Buchanan, F.R.S., Transactions of the 

 Royal Society of Edinburgh (1899), xxxix. p. 549. (Above, p. 151.) 



