252 Mr. J. Y. Buchanan [May 8, 



In Table I. we have, under «;, the vohime, in cubic centimetres, 

 of ice, the melting of which is induced at the temj^erature t by the 

 presence of 1*5105 gram chloride of sodium. The values of ?' arc 

 derived from determinations of the freezing-point of solutions of 

 chloride of sodium. Under v: (= 0*9167 v), we have the volume of 

 water so produced, and under c {= v - iv), the contraction due to 

 the melting. The cryohydric temperature of solution of chloride of 

 sodium is taken as - 21" "72, and its concentration as 20 -97 grams 

 salt in 100 grams water. 



The coefficient of cubic dilatation by heat of pure ice is taken as 

 0* 00016, and it is assumed to be constant at the temperatures under 

 consideration. The specific gravity of pure ice at t referred to that 

 of water at the same temperature, is taken as 0-9167. Tlic volume 

 of the salt diffused through the ice is disregarded. 



Using these constants, and those of Table I., we will apply the 

 principle to the discussion of the apparent variations of volume of a 

 block of ice, the volume of which at O'' C. is 1000 c.c. It contains 

 diffused through it 1*5105 gram NaCl, which we assume to be pro- 

 visionally in the i/iert state, in which it is deprived of the power to 

 induce the melting of ice at temperatures between 0' C. and 

 -21° -72 0. Let the temperature of the block containing the inert 

 NaOl be reduced to - 25° C. ; its volume will be reduced to 996-000 

 c.c, and as the temperature is below the cryohydric temperature, the 

 salt is by nature inert ; at such temperatures ice and common salt are 

 indifferent to each other. Let the temperature of the block of ice 

 be now^ raised to - 22" ; the salt remains inert, and the volume of 

 the ice increases to 996-48 c.c. If the temperature is further 

 increased to -21*^*721, the NaCl will still remain inert, and the 

 volume of the ice will become 996*525 c.c. 



If the heating is continued the temperature rises exactly to the 

 cryohydric point, -21"* 72, at which temperature the indifference of 

 chloride of sodium to ice ceases, and induced melting at that tem- 

 perature takes place. It will then be observed that the temperature 

 remains constant for a time, while the volume of the block dimin- 

 ishes. When the temperature begins to rise, the volume of ice melted 

 will be 5*498 c.c. As this produces 5*040 c.c. water, the diminution 

 of volume is 0*458 c.c, and the apparent volume of the block is 

 996*067 c.c 



Let us now go back to the initial state, in which we have the 

 block of 1000 c.c. ice, containing 1*5105 gram inert NaCl diffused 

 through it, at the temperature 0" C. Let the temperature be reduced 

 to -21°C., the ice remaining inert. The volume of the ice will 

 then be 996*64 c.c Let the NaCl recover its activity, it will melt 

 5*629 c.c ice, producing 5*160 c.c. water under a contraction of 

 0*469 c.c, so that the apparent volume of the ice at -21°C. is 

 996*64 - 0*469 = 996*171 c.c. 



By the aid of Table I. and the other constants we can calculate 



