218 Chemistry. [Lecture 31. 



floats on spirit of wine, and on every fluid yet 

 known ; its weight to that of water being as seven 

 and a half to ten. It is so volatile, that it im- 

 mediately evaporates, and spreads itself all 

 through the surrounding atmosphere. 



As it eviiporates very soon in this spontaneous 

 way, so it very soon arrives at its boiling point, 

 which is 100 degrees Fahr. But its boiling 

 point in vacuo appears from some experiments 

 of Dr. Cullen far below frost ; wherefore if the 

 pressure of the air did not keep its particles to- 

 gether in all the variations that happen here, 

 ether would never appear in any other form 

 than that of an elastic fluid, like air. 



After having shown that the evaporation of 

 fluids is attended with considerable cold, Dr. 

 Cullen repeated his experiments in vacuo. 

 Among other fluids he tried ether, in a phial 

 surrounded by water. On exhausting the air 

 the ether boiled violently, and the water was 

 converted into ice. Upon the evaporation of 

 the ether, the sensible heat was converted into 

 latent heat, which necessarily produces cold suf- 

 ficient to freeze water. 



Nitrous ether is made by gently distilling spirit 

 of wine with one half its weight of strong nitric 

 acid. The mixture thus distilled has a peculiar 

 fragrance. At first the nitrous ether was only 

 considered as a composition of spirit of wine 

 and nitric acid, till a French chemist obtained 

 ether from a mixture of this kind. He mixed 



