110 THE SAP. [LECT. m. 



immediately rendered it milky, and threw down a 

 white precipitate. The acetate of barytes threw 

 down a white flocculent precipitate; and by acetate 

 of lead (Goulard's extract), a white curdy preci- 

 pitate was also produced. No change was effected 

 on it by the solution of ammonia, nor by that of 

 gelatin : nor was any dark hue communicated by 

 the sulphate of iron. The addition of alcohol to 

 this sap threw down a light flocculent precipitate, 

 of a mucous nature. The sulphuric acid added to 

 it, occasioned a slight effervescence, and evolved 

 the odour of acetous acid. The conclusions which 

 may be drawn from these appearances is, that this 

 specimen of the sap of the Vine contained acetate of 

 potash with perhaps an excess of acid ; carbonate of 

 lime, vegetable mucilage, some albuminous matter 

 and water. As no effect was produced by the addi- 

 tions of the sulphate of iron and the solution of 

 gelatin, we conclude that it contained neither tannin 

 nor gallic acid, and therefore possessed no astrin- 

 gent property : a proof that the sap which we tried 

 was pretty pure, for some of the secreted fluids of 

 the Vine are both very acid, and considerably 

 astringent. The small quantity of sap which was 

 obtained, owing to the rather advanced state of the 

 season, for such an experiment, prevented the pro- 

 portions of the different ingredients from being 

 ascertained. 



M. Vauquelin, as I have already mentioned, 

 made the most interesting experiments, which 



