272 Journal of Agricultural Research voi.xx,No.4 



The principal factors involved in the tempering of wheat are (i) time, 

 (2) amount of water added, and (3) temperature. These factors vary 

 somewhat with different varieties of wheat. The general practice of 

 millers seems to be to temper from 12 to 48 hours and to add sufficient 

 water to make the total moisture content 15^2 per cent. There does 

 not seem to be any fixed temperature used. Some millers pay no atten- 

 tion at all to this factor, while others "warm" the water before adding 



it to the wheat. 



EXPERIMENTAL WORK 



Three varieties or lots of wheat were used for the experimental work — 

 a variety of hard wheat known as Kanred, developed recently by the 

 Kansas Agricultural Experiment Station; a hard, red wheat (Turkey or 

 Kharkof) from central Kansas; and a soft wheat from Colorado. This 

 latter variety came to the department as Arizona White wheat. 



The only chemical changes considered in this study were changes in 

 the (1) hydrogen-ion concentration, (2) total acidity, (3) water-soluble 

 phosphorus, and (4) titrable nitrogen. Yields of straight flour were also 

 computed, and the milling qualities were judged as nearly as possible. 

 Other investigations under way at the present time will be reported in a 

 later paper. 



Preliminary experiments were first conducted, from the results of which 

 it seemed advisable to compare different periods of time, different tem- 

 peratures, and different moisture contents as follows: (1) Time, 24 hours, 

 48 hours, and 72 hours; (2) temperature, 5 , 20 , and 40 C; and (3) 

 moisture content, 15X and 18 per cent. The preliminary experiments 

 seemed to indicate that the best results would be secured within these 



limits. 



APPARATUS AND METHODS 



The wheat was ground in a small burr mill driven by an electric motor. 

 This mill was so made that it could be taken apart easily and cleaned. 

 In addition, it was fitted with bran and flour sieves of silk bolting cloth. 



The wheat was tempered and extracted in a large water thermostat 

 fitted with a stirring device run by a small water motor. The thermo- 

 stat was heated by a gas burner, and the temperature was kept constant 

 (within i° C.) by means of a mercury gas regulator. 



The same hydrogen-ion apparatus was used as that described in a 

 former paper, 1 excepting that the saturated potassium-chlorid electrode 

 was used instead of the normal potassium-chlorid electrode. 



The original moisture content of each lot of wheat was determined by 

 drying in the air oven at 110° C. to constant weight. This was found to 

 be 12.65 P er cen t Ior Kanred, 10.86 per cent for the Hard Red winter 

 wheat, and 10.80 per cent for the Arizona White. In preparing the 

 wheat and flour samples 200 gm. of wheat were weighed out into a 

 500-cc. bottle. To this was added sufficient distilled water to bring 



1 Sw anson, C O., and Tague, E. L. determination of acidity and titrable nitrogen in wheat 

 with the hydrogen electrode. In Jour. Agr. Research, v. 16, no. i, p. 1-13, 6 fig. 1919. 



