Jan. 6, 1919 



Determination of Acidity and Nitrogen in Wheat 



3. A volt reading of 0.760 (Ph 8.3) corresponds to the point of color 

 change of phenolphthalein. The reading 0.820 (Ph 9-3) corresponds to 

 the point of color change for thymolphthalein. This was determined by 

 adding these indicators at the points mentioned. 



4. The amount of N/20 of barium hydroxid used to titrate to Ph 8.3 

 is greater than the amount used to titrate to Ph 7. and the amount used 

 to titrate to Ph 9.3 is greater than the amount used to titrate to Ph 8.3, 

 and these differences show a progressive increase as the time of digestion 

 is increased from 5 minutes to 24 hours. 



5. The values obtained at 20° C. are lower than those at 40° and at 

 50°. At 5° they are the lowest. x\t this temperature very little or no 

 hydrolysis takes place. Hydrolysis, as well as proteolysis, is most active 

 at 40°. 



6. The amount of N/20 barium hydroxid required to titrate to Ph 7 

 at 40° C. increased but little after 16 hours. In titrating to Ph 8.3 or 

 Ph 9.3 there is very little increase after 4 hours. For example, hydrolysis 

 is slightly slower at 20° than at 40°, and also slower at 40° than at 50°. 



7. At the end of 4 to 8 hours at 40° C, when hydrolysis is practically 

 complete, three times the number of cubic centimeters are required to 

 titrate to Ph 8.3 as are necessary to titrate to Ph 7. and four times as 

 many are required to titrate to Ph 9-3- 



8. The number of cubic centimeters used to determine the titrable 

 nitrogen after the addition of formaldehyde shows a progressive increase 

 with the duration of digestion, but the maximum is reached in about 

 two hours, at 40° C. At 20° the increase is much slower and continues 

 to the end of 24 hours. At 50° the final results obtained are lower than 

 those at either 20° or 40°, but show no increase or decrease correspond- 

 ing with the time. At 5° there is very little increase from 5 minutes to 

 24 hours. The number of cubic centimeters required to titrate to a 

 definite point were only about one-third as many as those required to 

 titrate to the same point at 40°. 



9. The most outstanding result shown in Table I is the fact that, while 

 the hydrogen-ion concentration shows no increase with the duration of 

 digestion, the amount of N/20 barium hydroxid used to neutralize to a 

 given hvdrogen-ion concentration increases in proportion to the duration 

 of the time of digestion. A definite limit, however, is soon reached. 

 This limit is reached soonest at the highest temperature. 



10. The digestion of ground wheat in water produces a substance 

 which is not ionized; yet it will neutralize definite amounts of standard 

 hydroxid, and these quantities correspond to a certain extent with the 

 duration and temperature of digestion. When the standard alkali is 

 added, it is ionized and the quantity present can be determined by the 

 method of titration. 



The results obtained with various concentrations at 5°, 20°, and 40° 

 C. are graphically presented in figures i, 2, and 3. 



