146 Professor Beck's Researches on Wines 



Vegetable Albumen. — Grapes, according to Berzelius, contain 

 a small portion of this substance, which he has described in the 

 fifth volume of his elaborate treatise on chemistry. In exa- 

 mining a specimen of American wine, which was said to be 

 the pure juice of the grape, I found, that when evaporated to 

 about one-eighth of its bulk, upon adding a portion of alcohol, 

 there was a deposit of a strong dark coloured matter, soluble in 

 water, and in solution of ammonia, but insoluble in sulphuric 

 acid. In these respects, it agrees very well with the descrip- 

 tion of vegetable albumen given by Berzelius. A portion of 

 pure Madeira, when treated in the same manner, yielded a bulky 

 white precipitate of saline matters. 



Sulphate of Potassa. — The presence of sulphuric acid in 

 wines is distinctly shewn by the dense precipitate which results 

 from the addition of muriate of barytes. I am not aware that 

 any other ingredient would produce this effect, except carbonic 

 acid, but the carbonate would be soluble in muriatic acid, which 

 is not the case with the precipitate in question. 



Tartrates of Potassa and of Lime.— The bitartrate of potassa 

 is one of the most abundant of the solid ingredients of wine, and 

 the tartrate of lime, as has already been remarked, is generally 

 associated with it. It is probably owing, in a great measure, to 

 the presence of these salts, that such dense precipitates are pro- 

 duced upon adding to wine the acetate of lead, or the nitrates 

 of tin, mercury, or silver. Insoluble tartrates of the metallic 

 oxides are thus formed. 



Tartrate of Alumina and Potassa. — This salt, according to 

 Berzelius, is especially characteristic of the German wines. 



Colouring Matter. — In the light- coloured wines, the colour 

 is supposed to be derived from the extractive matter ; but in 

 the red wines there exist tannin and colouring matter, the last 

 of which may be obtained, according to Robiquet, in a crystal- 

 line form. 



Red wines are sometimes imitated by the dealers in wine, by 

 adding to white wine other colouring matter, as, for example, 

 Brazil wood, logwood, the red beet, elder berries, &c. The 

 detection of these falsifications has engaged the attention of 

 many chemists. 



Vogel proposes the mixing of the suspected wine with the 



