46 Journal of Agricultural Research voi. xviii, no. i 



7. A volumetric pipette, capacity 25 cc. 



8. A volumetric pipette, capacity 150 cc. 



9. An alcoholic solution of phenolphthalein (0.15 to i per cent strength). 



10. A NJ20 solution of sodium hydroxid. 



11. A supply of distilled water, previously freed from carbon dioxid by boiling, 

 kept on hand in the refrigerator or immersed in ice water. 



PREPARATION OF SAMPLE 



All materials to be tested for acidity should be in a finely divided state in order 

 to make possible a complete and rapid extraction of the acids. It is also to be borne 

 in mind that cereal products usually undergo rapid changes in acidity after they 

 have once been ground. 



METHOD OF MAKING THE TEST 



Weighed quantities of the finely ground materials, for example 15 gm. of each 

 sample, are placed in the dry extraction bottle, and a tenfold quantity of the pre- 

 cooled distilled water is pipetted into each of the bottles. The latter are now stop- 

 pered tightly, well shaken, and immersed in the flat-bottomed pan holding the ice 

 water. At 15-minute intervals they are momentarily removed from the bath to be 

 shaken vigorously. Unless this is done at the prescribed intervals, or oftener, accu- 

 rate results will not be obtained. While the extractions are in progress preparations 

 may be made for the filtrations. At the end of the extraction period (i hour for 

 oats, i>^ hours for com) the mixtures are immediately thrown upon dry folded 

 filters, the filtrates being collected in the graduated cylinders. The first few cubic 

 centimeters of each filtrate may be discarded. If filtration is slow, or during hot 

 weather, it is best to keep the filtrates cool by placing the graduated cylinder in 

 the pan wth ice water during filtration. A measured aliquot, for example 25 cc. of 

 each filtrate, is finally pipetted into a beaker flask, and titrated with the alkali, after 

 adding a few drops of phenolphthalein. It has been customary in this country to 

 express the acidity in terms of cubic centimeters of normal alkali required to neutralize 

 the acid extracted from 1,000 gm. of the material. For very accurate work allowance 

 would have to be made in the calculations for the volume occupied by the undis- 

 solved portion of the material, but for practical purposes this correction may be 

 omitted. 



The titration in the presence of phenolphthalein offers no difficulties, 

 except in cases where the grain product is strongly damaged and dis- 

 colored. In such cases the filtered extracts may show a deep yellow 

 color, and the endpoint of titration becomes difficult to recognize. This 

 difficulty, if met with, can be overcome by the use of colorimetric devices, 

 such as the apparatus employed by Liiers and Adler (4,^0). 



ACIDITY OF SOUND OATS OF PURE VARIETIES DETERMINED BY THE 

 ICE- WATER EXTRACTION METHOD 



It seemed of interest to examine by means of the ice-water method a 

 number of sound oats of known type and origin, and to compare their 

 acidities with those found for the more or less damaged oats listed in 

 Table I. Samples of pure strains of oats were secured from various 

 experiment farms of the Department of Agriculture through the Office 

 of Cereal Investigations, Bureau of Plant Industry. Two samples 



