On Ice and Brines 137 



cooling. The specific heat of the solution is taken as that of 

 the water which it contains, namely 0*965 for III, and 0*9825 

 for IV. The mean freezing temperature was 2*O5 C. for III 

 and i*O5 for IV. The latent heat of water freezing at o is 

 79-25. The specific heat of ice being 0*5, the latent heat of 

 water freezing at 2'O5 is 78*22, and that of water freezing 

 at i'O5 is 7873. In Experiment III the total heat ex- 

 tracted during the freezing was 4230 x 0*965 = 4082 heat 

 units (gramme-degrees), and dividing this by 78*22 we find 

 52*2 grammes as the weight of pure ice formed at 2*O5 C., 

 equivalent to this abstraction of heat. In Experiment IV 

 the heat abstracted was found to be 5193x0-9825 = 5102. 

 Dividing this by 78-73 we find 64*8 grammes as the equivalent 

 weight of ice formed. 



We have calculated the weight of ice which would be 

 found, first on the basis of the salinity of the solution ; and 

 second, on the basis of the observed thermal exchange, 

 assuming in both cases that, in the act of freezing, pure ice 

 is formed. Thus : 



TABLE III. 



The agreement between the two quantities of ice formed 

 as calculated by the different methods is as close as could be 

 expected, and renders probable the truth of the common 

 assumption that the solid body formed is pure ice. 



It was accepted by Guthrie, Riidorff, and others that, in 

 solutions of the salts occurring in sea-water, ice separates 

 out at first, and continues to separate out until the con- 

 centration has become many times greater than that of 

 sea-water. Assuming that in sea-water all the chlorine is 

 united to sodium, 85 per cent, of the water would have to be 



