238 COHESION OF SOLUTIONS. 



during their solution in water, the low tempera- 

 tures at which they congeal, and the high tem- 

 peratures at which they boil, are all determined 

 by their affinity for caloric, which holds them 

 in a state of chemical combination with water. 



Theory of Freezing Mixtures. 



It was before stated that no solution of a solid 

 in a liquid ever takes place without a transition 

 of caloric from the solvent to the solvend. The 

 truth of this proposition is strikingly illustrated 

 by the phenomena of freezing mixtures. 



When water is congealed into snow or ice, it 

 has a stronger affinity for caloric than in the 

 liquid state. Hence it is that when a Ib. of 

 water, at the temperature of 172F. is mixed 

 with a Ib. of ice or snow, the latter is dissolved, 

 and the mixture brought to the temperature of 

 32 proving that 140 of caloric have been at- 

 tracted from the water by the snow, and inti- 

 mately combined with it in a latent state during 

 the process of liquefaction. 



But there are many salts which abstract ca- 

 loric from snow, by which they are dissolved, 

 or chemically combined with the snow. Such 

 is the affinity of common salt for caloric, 

 that when mixed with its own weight of 

 snow, both at the temperature of 32, there 



