On the Analyfis of Wine. j^-^j 



treading them, if done with care, may mix with muft a quan-, 

 tity of colouring matter fufficient to make the mafs alfume a 

 very intenfe colour. When it is required to obtain wine free 

 from colour, the grapes are collecied while the dew is upon 

 them, and they are trod as little as poflible. 



The colouring principle is in part precipitated in the caflcfs 

 along with the tartar and the lees j and when the wine is 

 old, it is not uncommon to fee it entirely free from colour. 

 The colour then depofits ilfelf in pellicles on the fides of the 

 veflels, or at the bottom : it is fcea floating ia the liquid like 

 films, which render it turbid. 



If bottles filled with wine be expofcd to the fun, a few 

 days will be fufficient to precipitate the colourinc: matter in 

 large pellicles; and the wine lofes neither its perfume nor 

 its qualities. I have often made this experiment on the old 

 highly coloured wines of the fouth. 



To precipitate the principle of the colour, nothing is ne- 

 ceffary but to pour lime water into the wine. 'In this cafe, 

 the lane combines with the malic acid and forms a fait, 

 which appears in the liquor under the form of light fiakes- 

 Thefe flakes gradually depofit themfelves, and carry with 

 them all the colouring principle. The depofit is black or 

 white, according to the colour of the wine employed for the 

 operation. It often happens that wine is fufceptible of form- 

 ing a precipitate, though it has been completely freed from 

 its colour by a firfl: depofit ; which proves that the principle 

 of the colour has ftrong affinity to malate of lime. The co- 

 loured precipitate is infoluble both in cold and in warm 

 water. This liquid even produces no change in the colour. 

 Alcohol has fcarcely any effecl upon it, only it acquires from 

 it a flight tint of brown. 



The nitric acid dilTolves the colouring principle of this 

 precipitate. 



When wine has been reduced to the fi:ate of extraft, the 

 alcohol poured over it becomes ftrongly coloured, as well as 

 the water, though in a lefs degree. But, bcfides the colour- 

 ing principle which is then dilfolvcd, there is alfo a faccha- 

 rine extraftive principle which facilitates the folution. 



The colouring principle, then, does not appear to be of 

 the nature of rcfins; it prefents all the characters belono-ino- 

 to a very numerous clafs of vegetable produtls, which ap- 

 proach very near to feculae, without having all their proper- 

 ties. The greater part of colouring principles arc of this 

 kind : they are fohible by the aflillance of ixiractive matter, 

 and when freed from this medium they become fixed in a 

 lading manner. 



A a 4 LXI. Some 



