fi. STUDIES ON APPLES. 
the action progressed and the concentration increased, the odor of cara- 
mel appeared, but if the volume was kept constant the solution re- 
mained nearly colorless. There was nearly always left a black residue 
which consisted in part of pectic acid. This was soluble in alkali, from 
which acid threw it down in brownish flocks. From the reaction prod- 
uct, sulphuric acid was removed by barium carbonate. The filtrate was 
concentrated to a sirup and treated with alcohol, which yielded an 
abundant precipitate. The filtrate from the alcohol precipitate, evap- 
orated to dryness, consisted largely of sugar, recognized by the erys- 
talline form of the compound with sodium chlorid, reducing property, 
and by a weak fermentation. The presence of sugar explained the 
formation of the black substance, a material of the nature of humic 
acid. Boiling with sulphuric acid also gave rise to a peculiar odor, 
like that of benzoie acid. 
This author notes that pectins disappear during the ripening of 
fruits; for example, pears containing much pectin when stored in the 
fall yielded only 0.5 gram from 100 pears in the spring. It is sug- 
gested that the pectins may form malic acid when they disappear as 
pectins. 
Frémy“ now published an elaborate paper on the pectin bodies. 
Pectose was considered to be a substance analogous to starch. Pectin 
was prepared by boiling a fruit mare or a root mare with malice or 
citric acid, and also by precipitating a ripe fruit juice with alcohol. 
Its properties are given—neutral, soluble in water, insoluble in alcohol, 
not colored by iodin, not precipitated by neutral Jead acetate, and 
inactive to polarized light. 
Boiling pectin with water gave parapectin, which only differed 
from pectin in being precipitated by neutral lead acetate. Boiling 
pectin with dilute acid gave metapectin, like pectin and parapectin 
except that it was slightly acid and precipitable by barium ehlorid. 
Prolonged boiling with acids gave parapectic acid; the action of pectase 
(an enzym analogous to diastase) on pectin gave soluble pectosie acid - 
which gelatinized. Alkalis converted pectin into pectic acid, soluble 
in alkalis and precipitating on adding acid. Heating pectic acid to 
200° C. gave pyropectic acid. The author noted great difficulty in 
obtaining pure pectin. Further changes and other pectin bodies were 
described in an unsatisfactory way. The methods employed were not 
described and practically no experimental data were given. The work 
of Chodnew received no notice. The formation of sugar by the acid 
hydrolysis of pectins is denied, since, though the solutions are reducing, 
they are not active to polarized light and are not fermentable.’ A list 
of pectins with proposed formulas is contained in the paper. 
“J, pharm. chim., 1847, [8] 12: 13; Comptes rend., 1847, 24: 1046; Ann. Chem. 
(Liebig), 1847, 64: 383. 
’ The fact that pentoses undergo alcoholic fermentation with difficulty was discoy- 
ered later. See W. E. Stone, Amer. Chem. J., 1891, 18: 73. 
