1887 .] 
Mr J. Y. Buchanan on Ice and Brines. 
139 
On considering them, it was at once evident that the lowering of 
the melting-point of ice followed the concentration of the solution, 
hut the law deviated in all cases from that of strict proportionality 
to the amount of salt dissolved, in some cases to a greater extent 
than in others. In comparing the effects of different salts in solu- 
tion on the melting-point of ice, no simple connection could he 
traced between their absolute weights and the effects produced ; but 
on comparing chemically equivalent weights, a very close connection 
was discovered. This will he evident from the inspection of the 
tables. In each the first column contains the temperatures at which 
pure ice melts ; and in the parallel columns the percentages of 
chlorine, potassium, or hydrogen in the solutions of the salts 
indicated at the head of each column, when ice melts in them at 
the temperature indicated. The figures thus give numbers pro- 
portional in each table to the chemically equivalent weights of the 
different salts. They show at first that, whereas the presence of 
equal absolute weights in solution produces very different effects, 
the presence of chemically equivalent weights produces very similar 
effects. On closer inspection, it is seen that the effects are almost 
identical where the elements to which the common constituent is 
united belongs to the same group of the periodic series, and differ 
sharply where these elements belong to different groups. In the 
case of the chlorides of sodium and potassium the number expressing 
the percentage * of chlorine in the solution expresses equally the 
depression of the melting-point of ice in terms of the Centigrade 
scale. The same depression of melting temperature is produced by 
10 per cent, less of chlorine united to hydrogen, and by 30 to 35 
per cent, more of chlorine when united to magnesium, calcium, or 
barium. 
The results obtained with sea-water are also given, for comparison. 
It will be seen that it behaves very approximately as a solution of 
chloride of sodium containing the same amount of chlorine. 
It is perhaps not very astonishing that unit weight of potassium 
in saline solution should produce the same effect in lowering the 
melting-point of ice, whether it is united to Cl or I ; but it shows 
clearly how independent this action is of the general character of 
the body in solution when we find the effect produced by unit 
* All percentages are by weight. 
