BY CHEMICAL BEAGENTS. 349 



gundy, Port, Hermitage, Boussillon, Burgundy- Pom- 

 mard, Narbonne, Benicarlo. 



Sugar of lead, in white wines, invariably occasions 

 a flocculent precipitate least in Lachryma Christi, 

 rather more in Champagne, Muscadel, and Bordeaux- 

 Sauterne, still more in B/hine wine, Madeira, and 

 TenerifFe, and most of all in white Bergerac, and white 

 Cotes. 



Among red wines, Port gives the smallest precipi- 

 tate of a dirty brown colour, Tavella a more copious 

 dirty white one, Burgundy, Langlade, a very abundant 

 pale blue violet like, still more copious and darker 

 blue violet is yielded by Hermitage, Burgundy-Pom- 

 mard, and Benicarlo ; Bordeaux. St. George, Narbonne, 

 and Boussillon give a voluminous pale blue precipitate. 



All precipitates are soluble in nitric acid, which 

 makes the red wines bright red. 



Alum in white wines produces no precipitate, 

 makes the red wine redder, otherwise there is no 

 change. If potash be carefully added, so that the alu- 

 mina is not precipitated by it, a precipitate of alumina 

 more or less coloured appears in the white wines. 



In the red wines, in Tavella a dirty precipitate, in 

 Port wine and St. Greorge a dirty brown, in the others 

 a dirty blue precipitate, but entirely dependent upon 

 the quantity of alum and potash which are added ; so 

 that when a good deal of alum is added, the precipitate 

 may be violet, or even pale red. This reaction must 

 therefore be entirely rejected. 



