TESTING WHEAT FOR PROTEIN 9 
than potassium sulphate. This experiment was carried on at the 
greatest intensity of heat (see p. 5) for one hour. 
Data obtained from this study, shown in Table 3, fully substantiate 
the claims of Paul and Berry, 9 that it is necessary to have at least 10 
cubic centimeters of acid present to hold all the ammonia. 
Therefore, in consideration of the data as given in Tables 2 and 3, 
it is evident that at least 10 cubic centimeters of acid are necessary to 
hold the ammonia formed during the oxidation process at all inten- 
sities of heat. It is necessary to have 6 cubic centimeters of acid to 
care for heat and oxidation losses when 1-gram samples are digested 
at a medium intensity of heat, 5.8 cubic centimeters at low heat, and 
7.3 cubic centimeters at high heat, making the total quantity of acid 
necessary at the three intensities of heat; 15.8 cubic centimeters at 
low heat, 16 cubic centimeters at medium heat, and 17.3 cubic centi- 
meters at high heat. When a 2-gram sample is used, 4 cubic centi- 
meters additional acid must be used. 
These acid losses will be subject to slight variations, depending 
upon the draft in the fume tubes or hood. Strong drafts will add 
about 1 cubic centimeter to the total given. A strong draft reduces 
the oxidation time approximately 10 per cent. 
Under the heat and time conditions set forth in the preceding dis- 
cussion, it is evident that 20 cubic centimeters of sulphuric acid are 
sufficient to digest completely a 1-gram sample of wheat and that 25 
cubic centimeters of acid are sufficient to digest completely a 2-gram 
sample of wheat. 
Further observations were made noting the effect of 15, 20, 25, 
and 30 cubic centimeters of concentrated acid upon the rapidity of 
oxidation of 1-gram samples. Using 15 cubic centimeters of acid at 
the greatest intensity of heat, too much frothing results. With 20 
cubic centimeters of acid the digest cleared in 6^ minutes; with 25 
cubic centimeters, in 8y 2 minutes; and with 30 cubic centimeters in 13 
minutes. Thirty cubic centimeters of acid are too much at a high 
intensity of heat, as there is considerable bumping and spurting 
during the digestion process, which, no doubt, results in material 
losses. Protein determinations made at the end of 15 minutes, or 
before oxidation was complete, showed that oxidation had progressed 
further with 20 cubic centimeters than with any of the other quanti- 
ties of acid used. It is reasonable to suppose that if this takes place 
at high heat it will also take place at the lower intensities of heat. 
EFFICIENCY OF HEAT AND CATALYTIC AGENTS ON OXIDATION OF WHEAT 
SAMPLES WITH SULPHURIC ACID 
As was pointed out, the periods of digestion and the catalytic 
agents were numerous within the formulas used by the various col- 
laborators. Xo standard time or quantity of reagent was employed 
by the majority. The question arose as to the efficiency of heat and 
of these reagents in varying quantities as an aid to the rapid diges- 
tion of wheat samples. 
The influence of heat on the oxidation process was studied by di- 
gesting wheats of high and Ioav protein content for 30, 60, and 90 
minutes with- 20 cubic centimeters of concentrated sulphuric acid, at 
8 See footnote 8. 
13754°— 26 2 
