236 CONGEALING POINT OF SOLUTIONS. 



It is likewise owing to the powerful attraction 

 of such salts for caloric, that when dissolved in 

 water they are so difficult to congeal that is, 

 they require an intense degree of cold to ab- 

 stract from them that portion of caloric which 

 maintains them in a state of chemical com- 

 bination with water. When I come to treat of 

 freezing mixtures, it will be seen that solutions 

 of potass and chloride of lime, formed by mixing 

 them with snow, remain liquid at 82 and 83 

 below the freezing point of water. 



The same thing is true of many other salts, 

 though to a less extent. It is owing to the at- 

 traction of common salt for caloric, that sea 

 water will not freeze at 32, but requires a 

 farther reduction of temperature to produce the 

 effect, when it gives up a portion of its heat and 

 the salt falls down. When 30 per cent, of 

 common salt is dissolved in water, its freezing- 

 point is reduced to 0. Moreover, the cohesion 

 of the solution is so far augmented, that its 

 boiling point is raised to 224 F. 



In like manner, all those salts which have a 

 strong attraction for caloric, and therefore pro- 

 duce cold during their solution, lower the con- 

 gealing point of water, and elevate its boiling 

 point ; such as nitrate of potass, nitrate of soda, 

 acetate of soda, tartrate of potass, muriate of 

 ammonia, and many others.* 



* It is owing to the affinity of sulphate of soda for caloric, 



