TESTING WHEAT FOR PROTEIN 7 
Into 500-cubic-centimeter volumetric flasks were measured 20-cubic- 
centimeter portions of sulphuric acid, specific gravity 1.82, and made 
to volume. The acid present was determined by titrating against 
a standard solution of potassium hydroxide. Twenty-cubic-centi- 
meter portions of the same acid were then placed in 500-cubic-centi- 
meter Kjeldahl flasks with 10 grains of K 2 S0 4 and 0.7 gram yellow 
mercuric oxide, and the mixture was heated for the time necessary 
to digest a sample of wheat. This time varied with the heat inten- 
sity : With low heat, two hours; with medium heat, an hour and 15 
minutes; and with high heat, 45 minutes. At the end of each heating 
period, the acid was transferred to a 500-cubic-centimeter volumetric 
flask, made to volume, and the acid content determined as before. 
Ten determinations were made for each heating time to overcome 
any minor differences in the heat of the burners. The difference 
in quantity of acid present before and after heating was considered 
as the quantity volatilized by heating. Tests of acid losses were 
made, using the Kjeldahl 5 mixture with sodium sulphate instead 
of potassium sulphate. Tests were also made using the Gunning 6 
mixture, and the mixture recommended by the Kansas City Protein 
Referee Board. 7 
To determine the acid loss due to oxidation of the wheat samples, 
1-gram portions of wheat, varying in protein content from 8.09 to 
18.70 per cent, were digested at medium heat for 75 minutes (com- 
plete oxidation) with the Kjeldahl mix (10 K 2 SO 4 -0.7 HgO). At 
the end of this period, the acid remaining was transferred to 500- 
cubic-centimeter volumetric flasks and the acid content determined 
as before. Subtracting this value from the acid remaining after 
heating gave the acid loss due to the digestion of the 1-gram sample. 
The experiment was repeated with three samples using 25 cubic 
centimeters of acid and 2 grams of sample, measuring the acid con- 
tent of each flask before and after heating, and after heating with 
the samples. 
The data from these investigations are given in Table 2. They 
show that approximately 2 to 3.5 cubic centimeters of acid were lost 
by heating the acid together with the catalytic reagents. The small- 
est loss was obtained at the lowest intensity of heat and the loss 
increased as the heat was increased. 
No greater heat appears to be developed by any one of the three 
formulas as measured by subsequent acid loss. 
The acid loss owing to oxidation of the samples, when a 1-gram 
sample was digested, varied from 3.1 to 4.5 cubic centimeters. The 
average loss was 3.6 cubic centimeters. The total acid loss owing to 
heating of a medium nature and oxidation of a 1-gram sample was 
6 cubic centimeters. Not quite as much. 5.6 cubic centimeters, were 
lost when the heat intensity was low, whereas 7.1 cubic centimeters 
were lost when a high heat was used. The total loss owing to heat- 
ing of a medium nature and oxidation of a 2-gram sample was 9.8 
cubic centimeters. 
5 See footnote 1. 6 See footnote 2. 7 See footnote 3. 
