HEAT OR CALORIC. 



10. Cold produced by vaporization in vacuo, 

 by boiling ether. 



Water frozen 



" Let a portion of water, just adequate to 

 cover the bottom, be introduced into the ves- 

 sel, represented in the subjoined .drawing, as 

 suspended within a receiver. Over the wa- 

 ter, let a stratum of ether be poured, from an 

 eighth, to a quarter of an inch in depth. If, 

 under these circumstances, the receiver be 

 placed on the air pump plate, and sufficiently 

 exhausted, the ether boils and the water 

 freezes." 



1 1 . Congelation of water in an exhausted receiver, by the aid of 

 sulphuric acid. 



" In the preceding experiment, water is frozen by the rapid ab- 

 straction of caloric, consequent to the copious vaporization of ether, 

 when unrestrained by atmospheric pressure. In vacuo, water un- 

 dergoes a vaporization analogous to that of the ether in the preced- 

 ing experiment ; but the aqueous vapor evolved in this case, is so 

 rare, that it cannot act against valves with sufficient force, to allow of 

 its being pumped out of a receiver with the rapidity requisite to pro- 

 duce congelation. However, by the process which I am about to 

 describe, water may be frozen by its own vaporization." 



* This experiment is neatly performed by placing water in a watch glass upon a 

 stand, and covering it with a thin metallic cup into which the ether is poured : on 

 working the pump, the ether will boil, and the water will freeze ; thug freezing and 

 boiling are coincident, and the boiling is the cause of the freezing, and yet the boil- 

 ing fluid is as cold as that which is freezing. 



These experiments "are more apt to succeed promptly if the ether be good ; it 

 is well to wash it two or three times with water in a bottle, in a mode to be de- 

 scribed hereafter, and if the water which is used for freezing, has been just formed 

 from melted ice or snow, it freezes so much the quicker as it has less sensible heat 



