-On Ice and Brines 141 



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 solu- 

 tions of the salts indicated at the head of each column, when 

 ice melts in them at the temperature indicated. The figures 

 thus give numbers proportional 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 solu- 

 tion 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 belong 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 1 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 approxi- 

 mately 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 weight of hydrogen identical, 

 whether it is united to such opposite radicals as Cl or OK. 

 Table VI shows further the effect of valence. While a given 

 weight of hydrogen produces the same effect in solution, 

 whether it be united to the very different but both univalent 

 radicals Cl and OK, its effect is reduced by one-half when 

 united to the bivalent SO 4 . That valence is not the only 

 1 All percentages are by weight. 



