26 TRANSACTIONS OF THE focr. 20, 
This compound is insoluble in excess of barium hydrate, or in 
proof spirit. 
The reagents used are as follows: 
A saturated solution of barium hydrate, free from carbonate, 
approximately three-tenths normal, 
A +, solution of hydrochloric acid; a ;*%; solution of hydro- 
chloric acid. 
Proof spirit. 
Phenol-phthalein, alcoholic solution. 
PROCESS. 
Take about 1.5 to 3.0 gms. of the dried and coarsely ground 
grain or flour (which should be previously thoroughly freed from 
fats in a Soxhlet or other extraction apparatus), place it in a 
small mortar, and add not more than 25 ¢.c. of cold water (for 
hard grains, as corn, etc., use hot water), rub up to a thin 
paste, and transfer the liquid to a 250 c.c, flask; continue the 
operation until all is so transferred, using not more than 100 c.c. 
of water. Now heat the flask over a water bath, with occasional 
agitation, until the starch is completely gelatinized, remove 
from the heat, cool, and run in 50 c.c. of the baryta solution; 
then stopper the flask and shake well, remove the stopper, and 
fill up to the mark with proof spirit; again stopper the flask and 
shake well for two minutes, and set aside to allow the baryta 
starch to settle. Now determine the value of 10 c.c. of the ba- 
ryta solution in terms of 54, hydrochloric acid. When the ba- 
ryta starch has settled, remove the stopper and draw off 50 c.c. 
of the clear supernatant liquid, and determine the excess of 
baryta in it with =X, hydrochloric acid, finishing with the ;*> 
acid, and using phenol-phthalein as an indicator. ‘Two portions 
of the liquid should be so tested and the results averaged. The 
amount of barium hydrate originally taken (50 c.c.), less five 
times the excess present in 50 c.c. of supernatant liquid, is 
multiplied by 4.23+ and gives the weight of starch in the 
sample. 
Barium hydrate solution should be preserved from contact with 
carbonic acid with jealous care, hence it is best to use a reservoir 
and self-filling burette, both protected by soda-lime tubes; thus 
guarded, a solution will maintain its efficiency for many months, 
but it is well in all cases to test the barium solution for each de- 
termination. Time of operation, exclusive of extraction of fat, 
one to one and one-half hours. 
The following table will show how the factors 4.23 and 0.0324 
are derived: 
