iNSOLtJBLE CARBOHYDRATES OR MARC. 71 



chiefly of iron phosphate. It was insoluble or only slightly soluble in 

 hot water, but readily dissolved in alkali to a clear solution. 



The author discussed the difficulties in preparing pure metallic 

 derivatives for analysis, which he considered to be best prepared from 

 the alkali salt of pectic acid and a soluble salt of the metal. It is dif- 

 ficult to avoid inclosing excess of alkali or salt in the resulting jellies. 

 This source of error was removed b}^ squeezing out the salts and wash- 

 ing with water. The author so prepared and analyzed the calcium, 

 barium, sodium, and silver salts, obtaining the formula Gj 8 H 20 O a6 . 



Pectinic acid was named and studied by Chodnew, who obtained it 

 by boiling beet marc with hydrochloric acid, precipitating by alcohol, 

 and washing with alcohol and ether. It differed from pectin in having 

 a slight acid reaction. This author discussed the question of whether 

 pectic acid exists as such in plants. Beet marc yielded no pectic acid 

 to ammonium hydroxid, so that pectic acid may exist here in combined 

 form, perhaps joined to calcium. But the marc after twice boiling 

 out with hydrochloric acid (removal of pectinic acid?) still yielded to 

 potassium hydroxid a body which on precipitating with acid showed 

 all the properties of pectic acid. The author considered then that 

 there existed in beet marc, not pectic acid, but a mixture of pectinic 

 acid and a newty found acid uberpectic acid which he stated was 

 changed by potassium t^droxid into pectic acid, and was insoluble in 

 ammonia. These two pectin bodies, pectinic acid and uberpectic acid, f T 

 he considered to be the sources of pectic acid as usually prepared. \ 

 Similar results were obtained from apples, pears, and red and yellow 

 beets. It was suggested that Fremy's acid, obtained from unripe 

 gooseberries hy boiling with acid, might be pectinic acid. 



In support of the theory that pectin bodies exist combined with cal- / ~ 

 ciiim in beet marc, the author described an experiment in which beet 

 marc was allowed to stand with dilute l^drochloric acid. It became 

 soft and translucent. .On washing and adding a very little limewater, 

 it regained its opacity and harshness. 



Metapectic acid (cf. Fremy, p. 69), prepared by Chodnew by boiling 

 pectin with potassium hydroxid, gave precipitates with acids and salts 

 on standing, and a jelly with alcohol. Its lead salt treated with hydro- 

 gen sulphid gave a black colloidal solution from which it was impossible 

 to separate the lead sulphid. Its properties differed from those given by 

 Fremy in being not a penta-valent acid, not deliquescent in the air, and 

 forming no soluble salts with calcium or barium. Pectic acid boiled for 

 two hours with dilute mineral acid did not dissolve entirely to metapec- 

 tic acid as Fremy states. The author carefully described the phenom- 

 ena which occurred as the acid was boiled with dilute sulphuric acid 

 salts. The solution soon became colored red, and reducing with silver 

 and copper; formic acid and carbon dioxid were formed in small quan- 

 tity, the former recognized b} T its odor, and the latter by limewater. As 



