148 On Ice and Brines 



In Table IX are given the volumes occupied by the ice 

 (with inclosed brine) formed by freezing 100,000 c.c. (at o C.) 

 of a water containing chloride of sodium equivalent to 

 7 grammes chlorine in 1,000,000 cubic centimetres (at o C.). 



The volume (z/ 2 ) of the ice and brine formed on freezing 

 this water is compared with that (P) observed by Pettersson 

 in freezing a sample of the distilled water in ordinary use in 

 the laboratory. 



It will be seen that the volumes observed by Pettersson 

 agree very closely with those calculated for a water containing 

 7 parts of chlorine in a million, on the assumption that 

 the saline matter is contained entirely in adhering liquid 

 brine. 



The irregularities in the melting-points of bodies like 

 acetic acid, to which Pettersson refers, are without doubt due 

 to a perfectly similar cause. 



Also the very low latent heat observed by Pettersson for 

 sea-water is to be explained by the fact that the salt retains 

 a considerable proportion of the water in the liquid state even 

 at temperatures many degrees below the freezing-point of 

 distilled water. 



Thus, he made two determinations of the latent heat of 

 sea-water containing 1*927 per cent. Cl and 3^53 per cent. salt. 

 The freezing took place in the one case between the tempera- 

 tures -9 0< o and -7'47C., and in the other between 8'35 

 and 6'94C, and the results he found were 527 and 51*5. 

 The mean initial temperature in these two experiments is 



87C, and the mean final temperature - 7'2 C. At 



7'2C. ice would form on cooling, and would melt on 

 warming a solution of chloride of sodium containing 6-48 per 

 cent. Cl, which represents 11-87 per cent, of the sea salt. In 

 order to concentrate a brine containing 3-53 per cent, salt to 

 one containing 11*87 per cent, 70 per cent, of the water in it 

 must be removed. Hence in sea-water freezing at a final 

 temperature of - 7'2 C. there is formed 70 per cent, of ice, 

 and there remains liquid 30 per cent, of brine. Freezing 

 began at the mean temperature - 87 C., and the latent heat 

 of pure ice at this temperature is 75. Calculating the latent 



