150 On Ice and Brines 



chloride of sodium, for instance, a rough rule is to have such 

 an amount of salt dissolved in the brine that the percentage 

 of chlorine shall give the desired temperature in Centigrade 

 degrees below the freezing-point. In my experiments in 

 freezing sea-water in quantities of 300 grammes, I usually 

 made up the bath of 500 grammes pounded ice, 400 grammes 

 water, and 45 grammes common salt. When mixed, the 

 liquid contained about 4 per cent. Cl, and gave a temperature 

 a little below 4C. In the course of an hour the liquid 

 would contain 3 per cent, to 3-25 per cent. Cl, and the tem- 

 perature have risen to 3 C. By using such baths freezing 

 operations can always be kept completely in hand. 



