44 Researches on Wines and other Fermented Liquors. 
with it. Itis probably owing, ina great measure, tothe presence of 
these salts, that such dense precipitates are produced 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 Ber-. 
zelius, is especially characteristic of the German wines. 
Coloring Matter.—In the light colored wines, the color is supposed 
to be derived from the extractive matter ; but in the red wines there 
exist tannin and red coloring matter, the last of which, may be ob- 
tained, according to Robiquet, in a crystalline form. 
Red wines are, sometimes, imitated by the dealers in wine, by ad- 
ding to white wine other coloring 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 sub- 
acetate of lead. Pure wine gives, with this reagent, a greyish green 
precipitate ; wine that has been colored by Brazil wood or elder ber- 
ries gives a precipitate of an indigo blue color, and when the red beet 
or sandal wood has been employed, the precipitate is red. 
The following are the results of my experiments with the subace- 
tate of lead. 
When added to pure Madeira wine, the precipitate was of a light 
yellow (cream) color. 
Pure Port wine gave it, a greyish precipitate with a slight tint of 
green. . 
With infusion of logwood, the precipitate produced by the subace- 
tate was of a deep purple ; when the coloring matter was largely di- 
luted with water, the precipitate was less dense and of a lead color. 
With infusion of the red beet, the precipitate was of a puce color ; 
when largely diluted, the precipitate was of a pale red (salmon) 
color. 
In one of the wines which I examined, the subacetate of lead 
threw downa bulky purple precipitate, similar to that produced by 
its addition to infusion of logwood. I received this wine under the 
name of Torres Vedras. It was of a very dark color and was rep- 
resented to be an old wine. 
Berzelius states, that the coloring matter of red wines gives differ- 
ent colored precipitates with subacetate of lead, according to the age 
of the wine. Thus, in new red wine, the subacetate commonly throws 
down a blue precipitate ; this circumstance must greatly impair the 
value of this test. 
