38 THE GBAPE. 



PECTOSE A.ND PECTIK. 



One of the constituents of the cell-walls in which 

 the juice is enclosed appears to be (as we have already 

 seen, p. 34) an ingredient called pectose, which is in- 

 soluble in water. During the ripening of the fruit, 

 another substance is formed from this pectose, which 

 is soluble in water, and is called pectin. 



According to Eremy, this pectin is obtained from 

 grape juice by precipitating the lime with oxalic acid, 

 the liquid thus procured is precipitated with alcohol 

 dissolved in water, and again precipitated with alcohol 

 till it is quite pure. It then presents a thread-like 

 body, soluble in water, and capable of being precipi- 

 tated by means of alcohol in the form of a jelly, that 

 is, supposing a good deal of water to exist in it. The 

 constant increase of alcohol during the transformation 

 of grape juice into wine, precipitates this matter. It 

 is never met with in wine ; if it should be found in it, it 

 can only be in the sediment obtained by means of 

 basic acetate of lead ; for this and not sugar of lead 

 precipitates it. 



No connexion has yet been established between this 

 pectin and the development of ferment in the wine, 

 indeed but little is known of the peculiar properties 

 of pectin. Its composition may be designated by 

 C 8 H 6 O 8 although Eremy reckons it at eight times 



