Oct. 1,1919 Method for Measuring Acidity of Cereal Products 37 



No. 588 Falten filter). By pouring back the first few cubic centimeters 

 of filtrate a homogeneous extract was obtained which, as a rule, was 

 clear and easy to filter when it was obtained from sulphured oats. 

 The extracts from unsulphured oats filtered more slowly and gave 

 turbid filtrates. This turbidity, however, did not interfere with the 

 subsequent titration. Usually when the ice-water extracts of sulphured 

 oats were neutralized a white amorphous precipitate was formed, while 

 with unsulphured oats no such precipitation took place. With the 

 com meal samples 13 and 14 similar precipitations occurred upon 

 neutralizing. It was thought that through the high acidity of these 

 samples some constituents had been dissolved which are insoluble in 

 neutral liquids. However, this explanation does not cover all cases, 

 since precipitation also occurred upon neutralizing the ice-water extracts 

 of sample 7s, 9s, and los in the foregoing table, as well as the extracts of un- 

 sulphured samples 63 and 74 in Table V. Since the latter samples were two 

 years old it is possible that the age of a sample bears some relationship 

 to the formation of this neutralization precipitate. All manipulations of 

 the ice-water method were carried out in the cold-storage compartment 

 with the exception of the titrations. For the latter, a suitable aliquot 

 of the respective filtrate was pipetted out, usually 40 cc. Phenolphthal- 

 ein was very satisfactory as indicator, giving a sharp endpoint. It 

 was employed in a 0.5 per cent solution in 50 per cent alcohol, not 

 more than five drops were added to any of the aliquots, and the appear- 

 ance of a faintly reddish tint was taken as the endpoint of titration. 

 Methyl red could not be used in this work. In determining the acidity 

 by the alcohol extraction method the directions given by Besley and 

 Baston (5) were followed. The endpoint of titration of the alcoholic 

 extract is not very sharp, a fact which was recognized by Besley and 

 Baston in their bulletin and which constitutes one of the drawbacks of 

 their method. 



From Table I it is seen that the acidity values of natural unsulphured 

 oats obtained at commercial elevators are in every case higher if deter- 

 mined by Schindler's alcohol method than if determined by the simple 

 ice-water extraction method. If the latter values are used as a basis 

 of calculation, these differences show an average for samples i to 10 

 of well over 250 per cent, the smallest difference being 184 per cent 

 and the largest 372 per cent. They are therefore quite appreciable and 

 are doubtless to a large extent attributable to the alcohol content (7) 

 of the extract made by the Schindler method. Diflferences of the same 

 general kind are shown by the com meal samples 11 to 14, all of which 

 had been milled three years previously, samples 12 and 14 having been 

 dried with artificial heat and samples 11 and 13 having been stored 

 without drying. 



After being bleached with sulphurous acid, oats would naturally be 

 expected to possess a higher degree of acidity than before the bleaching. 



