202 
the electrolyte chosen must be non-poisonous. 
Lead acetate or basic lead acetate will precipi- 
tate pectin, but the precipitation is an irre- 
versible one, and the amount of lead absorbed 
or combined may be poisonous. For these 
reasons ammonium sulfate was chosen. Bige- 
low, Gore and Howard? in their review of the 
literature on pectin mention that in 1898 
Bourquellot & Herissey used ammonium sul- 
fate as a precipitant for pectin obtained from 
gentian root. Other than this no further use 
has been made of this precipitant for pectin. 
METHOD 
60 grams of dried apple pomace were boiled 
three successive times with 200 ec.c. of water, 
_ filtering after each boiling. To each of the 
100 ce. of filtrate 25 grams of ammonium sul- 
fate were added? and then heated to 70° C., 
whereupon the pectin was precipitated as a 
grayish white flocculent precipitate. The pre- 
cipitate was separated from the mother liquor 
by filtering. (The mother liquor can be evap- 
orated and the residue used again or the res- 
idue can be used as a fertilizer.) The pre- 
cipitate was dissolved in hot water and again 
precipitated with ammonium sulfate. Again 
it was filtered and the precipitate was removed 
from filter paper and dried at 60—70° C. and 
when dry was washed several times with cold 
water to remove adhering ammonium sulfate. 
The precipitate was dried again and its gel- 
atinizing power was tested by adding to a 1 
per cent. solution of the pectin 0.5 per cent. 
solution of citric acid and 65 gm. of sugar. 
This solution was boiled for 10-20 minutes 
and upon cooling a nice stiff jelly was pro- 
duced. The taste did not indicate the presence 
of ammonium sulfate and upon dissolving the 
jelly in hot water only a slight milkiness was 
produced when tested for sulfates. 
In order to determine whether the yield of 
2 Bul. 94 U.S. Dept. Agr. Bur. Chem. 
SIf wet pomace is used it will require a some- 
what larger amount of ammonium sulfate. First 
add 25 grams per 100 c.c. and if precipitation does 
not occur, add successive portions of 5 grams until 
precipitation occurs. The pectin may also be pre- 
cipitated by saturating the solution in the cold 
with ammonium sulfate. 
SCIENCE 
[N. 8. Vou, XLVIII. No. 1234 
pectin by the above method was equal to the 
yield produced by the alcohol precipitation 
method, two samples of apple pomace from the 
same lot were treated exactly alike, except that 
ammonium sulfate was used in one case and 
alcohol in the other as the precipitating 
medium. The pectin was dissolved and re- 
precipitated in each case, then filtered and the 
precipitate was removed from filter paper and 
dried. The ammonium sulfate was removed 
from the one by washing with cold water, 
again dried and weighed. The amount of 
pectin recovered by each method is recorded 
in table below. 
Precipitant Pectin, Per Cent. 
Ammonium sulfate ........... 6.33 
ATCOnOL Ta ae tieerarstaerererecsermerte 6.91 
The amount of ammonium sulfate used can 
be reduced by concentrating the extract, 
either by evaporating on a steam bath, in a 
partial vacuum or by freezing.* The quality 
of the pectin is not impaired in either case. 
SUMMARY 
Pectin can be prepared by adding ammon- 
ium sulfate to the hot water extract of fruit, 
and heating to 70° C. The amount of pectin 
recovered is practically equivalent to that re- 
covered by the alcohol precipitation method. 
Concentrating the pectin extract below the 
boiling point did not impair the quality of the 
pectin. 
Cuas. H. Hunt 
WASHINGTON AGRIC. HXPERIMENT STATION, 
PULLMAN, WASH. 
4J. S. Caldwell, Bul. 147, Wash. Agr. Exp. Sta. 
SCIENCE 
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