InielUgence mid Miscellaneous Articles. 471 



ANALYSES OF PECTIC ACID. BY M. V. REGNAULT. 



The properties of pectic acid were carefully studied by M. Bra- 

 connot, who first extracted it in a pure state from the roots and barks 

 of trees. But the composition of this acid, which acts so important 

 a part in vegetable organization, is entirely unknown to us. 



M. Regnault obtained pectic acid nearly by the process given by 

 M. Braconnot. 



White turnips freed from their rind were reduced to as fine a pulp 

 as possible, and then washed seven or eight times with rain water. 

 After each washing, the pulp was pressed in small cloth bags. 

 The pulp thus completely lost its smell and taste ; it was then boiled 

 for three quarters of an hour with 10 or 12 times its weight of water 

 and a tenth of carbonate of soda ; after which it was collected upon 

 a cloth, washed with a small quantity of water, and pressed. 



A solution of chloride of calcium was poured into the solution of 

 pectate of soda, which occasioned an abundant precipitation of gela- 

 tinous pectate of lime, mixed with much carbonate. This precipi- 

 tate was for a long time washed upon a cloth, pressed, and then 

 dried in the air. It was this impure pectate of lime which afterwards 

 served for the preparation of the pectic acid and pectates. To separate 

 the pectic acid from it, it was digested for 8 or 10 hours at a tem- 

 perature of 11 2° to 140° F. in very dilute hydrochloric acid. The pectic 

 acid set free was collected on a filter and washed with distilled water ; 

 it was of a deep colour, and was dissolved in ammonia ; the solution 

 was very gelatinous, and could not be filtered, and was put to digest 

 for 24 hours with animal charcoal at a temperature of 140° to 1 76° F. 

 By this it became quite colourless, lost its viscidity, and readily 

 passed through the filter. On supersaturating the ammoniacal so- 

 lution with hydrochloric acid, fresh pectic acid was separated, which 

 was now in the state of a perfectly colourless jelly. This jelly 

 ought to be washed for a long time, first with water acidulated with 

 hydrochloric acid, then with distilled water. It is however rarely 

 thus obtained quite pure ; it usually leaves after burning a small re- 

 sidue of earthy matter, which adheres to it with the greatest obsti- 

 nacy. It is to be redissolved in ammonia or its carbonate, and to be 

 again precipitated from solution. Gelatinous pectic acid cannot be 

 pressed through a cloth, but must be dried in a stove. When dry 

 it is horny, colourless and translucid, extremely hard, and difficult 

 to reduce to powder. It has a sHghtly acid taste. When digested 

 in hot water it softens, swells a little, but never regains its original 

 gelatinous state. Gelatinous pectic acid is perfectly insoluble in 

 cold water ; it appears to dissolve in small quantity in hot water, 

 and especially by long digestion. For if it be boiled for several hours, 

 the filtered solution gives a soluble precipitate with chloride of cal- 

 cium ; but it does not precipitate any thing by mere cooling. When 

 pectic acid is heated, it melts, swells, and leaves a charcoal difficult 

 to burn. 



Dilute nitric or hydrochloric acid, even when heated, does not 

 act upon it ; strong nitric acid attacks it rapidly, and oxalic and 

 mucic acid are formed. Cold concentrated sulphuric acid does not 

 appear to act upon it, but when heated decomposes it readily. 



