and other Fermented Liquors. 147 



subacetate of lead. Pure wine gives, with this re-agent, a 

 greyish-green precipitate ; wine that has been coloured by Bra- 

 zil wood or elder berries gives a precipitate of an indigo-blue 

 colour ; and when the red beet or sandal wood has been em- 

 ployed, the precipitate is red, The following are the results 

 of my experiments with the subacetate of lead : 



When added to pure Madeira wine, the precipitate was of a 

 light yellow (cream) colour. 



Pure Port wine gave it a greyish precipitate, with a slight 

 tint of green. 



With infusion of logwood, the precipitate produced by the 

 subacetate was of a deep purple ; when the colouring matter 

 was largely diluted with water, the precipitate was less dense, 

 and of a lead colour. 



With infusion of the red beet, the precipitate was of puce 

 colour ; when largely diluted, the precipitate was of a pale red 

 (salmon) colour. In one of the wines which I examined, the 

 subacetate of lead threw down a bulky purple precipitate, simi- 

 lar 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 colour, and was represented to be an old wine. 



Berzelius states, that the colouring matter of red wines gives 

 different coloured precipitates with subacetate of lead, accord- 

 ing to the age of the wine. Thus, in new red wine, the sub- 

 acetate commonly throws down a blue precipitate. This cir- 

 cumstance must greatly impair the value of this test. 



Nees d'Esenbeck has proposed a method of detecting artifi- 

 cial colouring matter in wine, which is said to be more certain 

 in its indications. This consists in dissolving one part of alum 

 in eleven parts of water, and one part of carbonate of potassa 

 in eight parts of water. The wine is mixed with its own bulk 

 of the solution of alum, which renders its colour more bright. 

 To this, the alkaline solution is now added, little by little, tak- 

 ing care not to precipitate the whole of the alumina. The alu- 

 mina precipitates with the colouring matter of the wine in the 

 form of a lake, whose shade of colour varies with the nature of 

 the colouring matter, and which, when combined with an excess 

 of potash, assumes another tint, also varying with the colouring 

 matter combined with the alumina. In order to obtain correct 



K 2 



