ON THE SUGAR OF GRAPES. 353 



If the wine be filtered when at Its greatest degree of opa- Filtering checkc 

 city, its fermentation is perceptibly checked: but it after- ^l'^ ^^y™^"^** 

 ward revives, and pursues its course without depositing any again revives. 

 thing but particles of fecula and pure tartar. This fccula, The fecula. 

 or second lees of wine, is always loaded with tartar: but 

 when it has been copiously w ashed, we find in it all the cha- 

 racters on which Thenard has insisted, and particularly 

 those appearances, that have led BerthoUet to compare it 

 with starch. It is perfectly insoluble; grows sour, fer- 

 ments, and acquires the bad smell of the gluten of wheat; 

 in a word it becomes cheese. When it is dry it is a littla 

 transparent, horny, and affords all the products of animal- 

 ized matters. Potash dissolves it, and separates it from the 

 parts that are purely fibrous. In fine, it is the same thing 

 as the unc'larified must rejects in the first moments of fer- 

 mentation ; and if it do not separate from it at the same 

 period, it is because its solubility retains it in the liquor, 

 till the alcohol <iomes to precipitate it. Other circumstances 

 confirm the fact, that this fecula is no more necessary to the 

 transformation of the two sugars into alcohol, than the 

 former, or than the gum, extractive matter, tartar, kc. 

 If we take must saturated and clarified with whites of eggs, 

 fermentation commences in it the next day. It pursues its 

 course without depositing any fecula, but tartrite of lime 

 alone; and without yielding any thing but carbonic acid. 



In the fipace of a month the liquor falls from 17° on theTne liquor 

 areometer to i^i or 2«. If we analyse the residuum after ^^"^""^^^.^^JS*^^^^^^ 

 distillation, we shall find again the gum, malic acid, ex- 

 tractive matter, vinegar, some remains of sugar, and no- 

 thing more. 



The muscovado brought to l?'^' by a sufficient quantity Fecula has no- 

 of water ferments completely, changes into wine, and de- ferlnentati'on'^ 

 posits but a few particles of matter. Where then is the 

 influence of the fecula, the tartar, the acids, and the ex- 

 tracts ? But the best clarified must will no doubt retain a 

 portion of fecula ; and it may be said, that this excites fer- 

 mentation in the sugar. If this be the case, I would a^i- 

 swer, the fermentation should be weaker in proportion to 

 the loss of this principle occasioned by the clarification of 

 the must; but we do not find, that this is at all behind that 



Vol, XXL— Suppleme>-t. 2 A which 



