160 Chemistry. [Lecture 29. 



water upon it, and may be afterwards crystal- 

 lized. The sublimed particles returned and sub- 

 jected to the same operation, put on the same 

 vitreous appearance. 



Boracic acid has but little attraction for water 

 (i. e. for more than it always contains). It dis- 

 solves but in small quantities in cold, and not 

 much in hot water; it crystallizes again when 

 cool in little transparent whitish icicles. Its 

 properties as an acid are very weak ; it has no 

 taste at first, but afterwards gives a sensation of 

 bitterness. Its effects are still weaker upon the 

 vegetable tinctures than even the vegetable acids : 

 sometimes it does not affect them, and when it 

 does, I apprehend it is from some other acid it 

 contains. Tried upon tincture of roses and vio- 

 lets, it had no effect. Litmus (which is more 

 delicate, being a preparation of one of the 

 mosses used in dying, and which is purplish) it 

 changed into a sensible red. 



Boracic acid effervesces with a boiling hot al- 

 kaline solution, but not with metals or absorb- 

 ent earths, though it may be united with them. 

 It has a weak attraction for inflammable sub- 

 stances, particularly spirit of wine, the flame of 

 which it tinges green ; hence it has been thought 

 to contain some copper, but we have no proof 

 of this. 



Lastly, t\\e fluoric, extracted from the fluor 

 or beautiful Derbyshire spar (which is a fluat of 



