458 COMPOUND PRODUCTS. CHAP. I. 



is agitated but slightly a froth is formed on the sur- 

 face ; and if it is kept for any length of time in a 

 close vessel it ferments and effervesces spontane- 

 ously, and at length becomes strongly acid, assum- 

 ing a blueish colour and a turbid appearance. At 

 last it deposits a sediment, and resumes its transpa- 

 rency, but forms at the same time a thin and 

 mouldy pellicle on the surface. 



If exposed to the action of fire it emits bubbles 

 of carbonic acid gas, exhales a strong odour of 

 vinegar, and yields by distillation carbonate of am- 

 monia. Its charcoal contains carbonate of potass, 

 carbonate of lime, and muriate and sulphate of 

 potass. It combines in all proportions with water, 

 which dilutes and dissolves it when thick and viscid. 

 Strong acids deprive it of the carbonic acid and 

 acetous acid which it contains, and occasion the 

 formation of carbonate of lime and acetate of potass 

 which it previously held in solution. Alkalies com- 

 bine with it readily, and saturate its excess of acid. 

 They resist its tendency to spontaneous decomposi- 

 tion, and retain in solution its extract.* 



But the best account of the properties of the sap, 

 and the most complete ?> t of experiments on the 

 subject, are those of Deyeux and Vauquelin. Deyeux 

 analyzed the sap of the Vine and Elm, and found 

 in it acetate of lime, ae -tous acid, and an extract 

 to which he attributed tl o formation of ammonia, 

 * Systme des Co: (.ais. vol. viii. p. 130. 



