INSOLUBLE CARBOHYDRATES OR MARC. 69 







organic acids, but was readily thrown out of solution as a jelly by a 

 trace of mineral acid or alkaline earth salts. The jelly was moro solu- 

 ble in water than the pectin (pectic acid) from currants. 



Mulder "and Regnault* reported combustions of the metallic salts 

 of pectins and pectic acid. Mulder concluded that pectic acid prepared 

 by dissolving in alkali and precipitating with acid differed from pectin 

 only in its higher ash content. 



Fremy c contributed an important article treating of the difficulties 

 involved in this field of work and of the mutations of the pectin bodies. 

 Pectin was prepared from fruit juices by first boiling to coagulate 

 albuminous matters, filtering, and then repeatedly purifying by pre- 

 cipitating with alcohol and dissolving in water. The resulting body- 

 was white and soluble in water. It proved to be difficult to burn 

 quantitatively on account of its ash, which retained carbon dioxid; so 

 its lead salt was prepared and burned, the results indicating the formula 

 C 24 H 34 O 22 . Boiling this pectin with water increased the amount of 

 lead which would combine with it, an increase of t{ saturation capacity." 



The author states that pectins do not yield sugar on hydrolysis. 

 Pectic acid dissolved in dilute potassium hydroxid would no longer' 

 precipitate on adding acid, the salt of metapectic acid having been 

 formed. From the free meta acid, neutral lead acetate precipitated a 

 salt much richer in lead than the lead salt of pectic acid. The free 

 acid had an acid taste and was deliquescent. Long standing with 

 caustic potash reduced an acid of still greater "saturation capacity" 

 and more acid taste. Dilute acids effected a similar change in pectin 

 and pectic acid (see Chodnew, p. 71). The author considered that 

 the original pectin became hydrated in the above treatments and 

 could in this way combine with more lead. 



A discussion is given concerning the changes in the cell wall as 

 fruits ripen, the wall becoming thinner and the fruit less acid. The 

 presence of an insoluble mother substance of pectin-forming material, 

 later named pectose, residing in the cell walls of unripe fruits, is sug-* 

 gested, as a result of experiments on a fruit marc, which with boiling 

 water yielded only small quantities of pectin, but with dilute acid 

 gav 7 e it in abundance. 



Poumarede^ denied the existence of pectic acid in plants. He con- 

 sidered pectin to be an organized tissue, and pectic acid a reaction 

 product. 



Poumarede and Figuier^ considered pectin and "lignin" (cellulose) 

 to be identical. 



: 



Ann. Chem. (Liebig), 1838, 28: 280. 



&J. pharm. chim., 1838, 24: 201; J. prak. Chem., 1838, 14: 270. 

 clbid., 1840 [2], 26: 368. 

 dComptes rend., 1839, 9: 660. 

 ., 1846, 23: 918. 



