122 MR. EDWARD SCHUNCK ON SOME 



much that it is difficult to identify any member of the class 



by means of analysis only. The composition just given 



approaches that of Fremy^s parapectic acid, which, according 



to him, consists of 



C 41-67 



H 4'97 



o 5336 



lOO'OO 



I have mentioned that the acid originally contained in 

 the alkaline extract of cotton is insoluble in water, but is 

 gradually converted during the process of purification into 

 a soluble acid. Of the insoluble acid, the true pectic acid, 

 I obtained on one occasion only a sufficient quantity for the 

 purposes of analysis. It was left undissolved by boiling 

 water in the preparation of the specimen of soluble acid 

 employed for the second of the above analyses, and when 

 dry was dark-grey and horn-like, and was with difficulty 

 reduced to powder. 



0*5270 grm. of this substance gave 07880 grm. carbonic 

 acid and 0-2315 grm. water. 



0*6400 grm. left 0*0200 grm. of ash=3*i2 per cent. 



After deducting the ash, these numbers correspond in 



100 parts to 



C 42*09 



H 503 



According to Chodnew *, pectic acid contains in 100 



parts 



C 42*22 



H 524 



o 52*54 



Fremy^s experiments led him to infer that there exists 

 in plants a body insoluble in water, which he calls pectose, 

 and which, by the action of acids, alkalies, or the pectic 

 ferment (pectase), is converted first into pectine, then into 

 pectic acid, and other products in succession. It is not 



* Annalen d. Chem. u. Pharm. B. li. S. 363. 



