INSOLUBLE CARBOHYDRATES OR MARC. 69 
organic acids, but was readily thrown out of solution asa jelly by a 
trace of mineral acid or alkaline earth salts. The jelly was more 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. 
Frémy ¢ 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,,H,,0,,. Boiling this pectin with water increased the amount of 
lead which would combine with it, an increase of ** 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 mare, which with boiling 
water yielded only small quantities of pectin, but with dilute acid 
gave 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. 
¢Ibid., 1840 [2], 26: 368. 
“Comptes rend., 1839, 9: 660. 
€Ibid., 1846, 28: 918. 
