THEORY OF FREEZING MIXTURES. 239 



is a transition of caloric from the snow to 

 the salt, by which they are intimately united, 

 and the temperature of the mixture reduced 

 9, or 41. Again, so powerful is the at- 

 traction of chloride of calcium for caloric that 

 when 3 parts of it are pulverized and mixed 

 with 2 of snow, both at 32, the temperature 

 and congealing point of the mixture are reduced 

 50 : and if 4 parts potass be mixed with 3 

 of snow, the temperature falls 51 or 83 in 

 all. But if 2 parts chloride of calcium and 1 of 

 snow be reduced 9, and put into the solution 

 of snow and salt, the temperature and freezing 

 point of this new mixture are reduced 74. 



That such salts attract caloric from snow is 

 evident from the fact, that if the chloride of 

 sodium and snow be cooled to 9, and then 

 mixed together, no solution or farther reduction 

 of temperature takes place and that if chloride 

 of calcium and snow be cooled from 32 to 50 

 before they are mixed, no chemical solution, 

 nor change of temperature occurs, because there 

 is no transition of caloric from one to the other. 



Many other salts have the power of absorbing 

 caloric from water, acids, and from snow, such 

 as nitrate of potass, nitrate of soda, muriate of 

 ammonia, muriate of zinc, sulphate of soda, &c. 

 If nitrate of ammonia be pulverized and mixed 

 with its own weight of water, at 50 F. the tem- 

 perature is reduced 46, that is down to 4, which 



