errs us pectin 3 
precipitated by the high percentage of alcohol used, and it was diffi- 
cult to completely wash out the sugars, acid, and soluble material. 
Campbell's method (10) also requires a large excess of alcohol. 
After many experiments, the following method was adopted: 
Filtered pectin solution (50 or 100 cc.) was added to l}4 volumes 
of 95 per cent alcohol, allowed to stand overnight, and filtered on a 
qualitative filter paper reinforced with a hard filter paper, using re- 
duced pressure. The precipitate was washed with 100 cc. of 60 per 
cent alcohol, followed by about 200 cc. of 95 per cent alcohol, removed 
from the filter while wet, and dissolved in about 40 cc. of water. The 
solution was reprecipitated and washed as before, finally using a 
little ether. The precipitate was removed from the filter, dried in a 
water oven for 4 hours, weighed, ignited, and reweighed. 
Although probably not as accurate as Fellenberg's pectic acid 
method (23) and the more recently published methods of Wichmann 
and ChernorT (57) and Carre and Haynes (13), the method was 
rapid and gave comparable results. 
PRELIMINARY EXPERIMENTS 
The literature contains many methods for the preparation of pectin 
in small quantities for the study of its chemical composition, but little 
on the details for commercial production. Many of the methods 
given produce pectic acid and related compounds instead of pectin 
(54). In a series of preliminary experiments, the methods of Hunt 
(84) j Magoon and Caldwell (38), Schryver and Haynes (43), and 
Clayson, Norris, and Schryver (15) did not yield pectins suitable for 
making fruit jellies. 
Vauquelin (55) in 1829 precipitated pectin from solution with 
alcohol, and Fremy (25) in 1840 produced powdered pectin with alco- 
hol. Caldwell (9) concentrates the pectin solution by freezing and 
then precipitates it with alcohol. 
The identity of the bitter principles in the peel of lemons and or- 
anges grown in the United States is not well established. The gluco- 
side naringin, found by de Vry (58) to be the bitter principle in grape- 
fruit (Citrus decumana), does not occur in other citrus fruits. The 
bitter glucosides isohesperidin and aurantiamarin have been found in 
some varieties of orange by Tanret (47), while the nearly tasteless 
glucoside hesperidin is present in practically all citrus fruits except 
grapefruit (49). Attempts made to destroy the bitter principles in 
the pectin extracts by means of enzymes or to remove them with 
chemicals were unsuccessful. In making pure pectins several in- 
vestigators have first washed the pectin-containing material, either 
before or after drying, with alcohol, acetone, and ether. This re- 
moves impurities, including the bitter principles from citrus residues, 
but requires a large quantity of solvent. 
Pectin extracts were dialyzed in collodion sacs in several changes 
of cold water until all of the acid and bitter principle had dialyzed. 
Although about 90 per cent of the solids not pectin dialyzed, at least 
50 per cent of the pectin passed through the membrane (Table 1). 
