68 STUDIES ON APPLES. 
herbaceous plants, in the cortical layers of trees, and in fruits. So con- 
stant was its occurrence in his researches that this author regarded 
it as one of the principal constituents of all plants. He considered it 
to be similar, if not entirely identical, with the principle in plants 
vaguely described as jelly. The method given by Braconnot for 
obtaining pectin (as pectic acid) from roots containing starch is to 
pulp the roots, wash out with water to remove sugar, then boil the 
mare with dilute hydrochloric acid, wash, and heat the starch-free and 
sugar-free mare with very dilute potash or soda. There results a 
mucilaginous slightly alkaline liquid, from which hydrochloric acid 
separates pectic acid as a jelly. So prepared, pectic acid had a feebly 
acid reaction to litmus and was slightly soluble in hot water, but the 
filtered liquor did not precipitate on cooling, and barely reddened 
litmus. It was, however, coagulated by alcohol, by metallic salts, and 
even by sugar. Dried on a capsule it appeared as transparent leaflets 
which loosened from the capsule as they dried. These were slightly 
swelled by cold water, and dissolved slightly in boiling water. <A 
potassium salt was separated by precipitating its water solution with 
alcohol, excess of alcohol extracting coloring matter and excess of 
alkali. This salt was very soluble in water, possessed a flat insipid 
taste, and yielded 15 per cent of potassium, calculated from the sul- 
phated ash. Its water solution was coagulated by salts, and by alcohol 
and sugar, and gave precipitates with solutions of salts of heavy 
metals. An ammonium salt was prepared which possessed properties 
similar to those of the potassium salt. The use of these salts for the 
preparation of jellies was suggested, and experiments are described in 
which beautiful jellies were obtained. 
The pectic acid was attacked only slightly by concentrated sulphuric 
acid in the cold. Nitric acid yielded oxalic acid and a white powder 
which was treated with ammonia to separate from calcium oxalate. 
The ammonia solution, acidulated, gave a granular crystalline sub- 
stance which he believed to be mucic acid. Braconnot concluded the 
article by proposing for this acid the name pectin, from the Greek 
word 77xKTis, meaning coagulum. 
Vauquelin“ worked on the carrot, obtaining pectin from the juice 
by boiling in order to clarify, then precipitating with alcohol; and 
from the mare (as pectic acid) by boiling with dilute caustic potash and 
precipitating with calcium chlorid, or better, barium hydroxid, filter- 
ing, treating the filtrate with sulphuric acid, and then with potassium 
hydroxid, finally precipitating with hydrochloric acid. Distilled or 
filtered rain water is stated to be necessary. 
Braconnot’ in 1833 described the pectin separated from oak bark by 
solution in alkali. It was not precipitated from solution in alkali by 
“Ann. chim. phys., 1829 [2], 41: 46. 
b Ann. Chem. (Liebig), 1833, 5: 275. 
