Chemical Effects of Caloric, $c. 73 



caloric suddenly emerges. These experiments 

 not only prove the existence of latent caloric 

 before the water freezes, but likewise that the 

 freezing does not depend on the diminution of 

 sensible heat; since we find it may retain its 

 fluidity, though cooled eight degrees below the 

 freezing point : nor does it depend merely on its 

 tranquillity; for, if it did, we should expect, upon 

 disturbing it, that the whole would be congealed. 

 This does not happen ; and the reason is, that a 

 quantity of latent caloric is impelled inwards, 

 which raises the temperature above thirty-two 

 degrees, below which it must fall before it can 

 be frozen. In the ordinary freezing of water 

 something happens like this, though by insensi- 

 ble degrees ; when water is exposed to freeze, be- 

 fore the whole of it is converted into ice, it must 

 all the time be imparting heat to the air. 



Several facts and phsenomena are explained 

 upon this principle, as the production of cold by 

 a mixture of ice with the nitric acid or saline 

 substances. If the nitric acid is mixed with ice 

 or snow, there will be a sudden liquefaction, 

 consequently a sudden absorption of caloric, 

 which will produce a degree of cold in the sur- 

 rounding region. 



Mixture in general promotes liquefaction. In 

 this instance a most intense cold is produced, 

 and the cause is as follows : If I can liquefy ice, 

 I know I must throw in a prodigious quantity of 

 obvious heat or caloric, and which must imme- 



VOL. II. E 



