26 TRANSACTIONS OF THE [oCT. 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 fg- solution of hydrochloric acid; a y^^- 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.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 Avell, remove the stopper, and 

 All 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 -^ 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 y^ 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: 



