THE GEAPE. 5 



(both grape sugar and fruit sugar), gelatine, or pectin ; 

 gum, fat, wax, vegetable albumen, vegetable gluten, 

 and some other substances of the nature of extractive 

 matters, which are not, however, accurately deter- 

 mined; tartaric acid quite free, and combined with 

 potash, as cream of tartar, partly also combined with 

 lime ; in some cases we find also racernic acid, malic 

 acid, partly -quite free, partly combined with lime 

 (Berard), according to some, tartrate of potass and alu- 

 mina ; further, oxide of manganese and oxide of iron, 

 sulphate of potash, common salt, phosphate of lime, 

 magnesia, and silicic acid may also exist. 



Up to this time no other ingredients have been dis- 

 covered in the juice of the grape, but other materials 

 must exist in it in small quantities, those, namely, 

 which appear during fermentation, and impart to the 

 fermented liquor, or at least tend essentially to pro- 

 duce not only the vinous smell common to all wine, 

 but the aroma (bouquet), and the flavour respectively 

 peculiar to each wine, in almost unlimited variety. 



In cases where the skins are allowed, as in the 

 preparation of red wine, to ferment with the juice, the 

 elements which impart odour and flavour may be 

 drawn from them. 



But experience has not sufficiently decided even 

 this point. What we know with certainty is, that 

 colouring matter, as also tannic acid, may be extracted 

 from the alcohol developed during the process of fer- 

 mentation; colouring matter and tannic acid are, 



