44 



Journal of Agricultural Research voi. xviti, No. i 



The acidity figures in Table IV will serve to illustrate these relations. 

 They are also intended to show the influence of the time of extraction 

 upon the acidities of the extracts of corn and oats. Three portions of 12 

 gm. each of finely ground oats were extracted with 100 cc. of ice water, 

 the bottles being shaken at 15-minute intervals. Three 12-gni. portions 

 of a commercial corn meal were extracted in the same manner. All six 

 extractions were started at the same time. At the end of i hour the con- 

 tents of one bottle each of the oat and corn infusions were poured upon 

 dry folded filters, and two 25-cc. aliquots of the filtrate pipetted into 

 Erlenmeyer flasks. The one aliquot was titrated at once with Njio 

 sodium hydroxid, while the other aliquot was left in the cold-storage 

 room for 24 hours before being titrated. The former aliquot, after being 

 neutralized, was returned to the cold storage. At the end oi 1% and 2 

 hours, respectively, the filtration of another infusion of both corn and oats 

 was begun, and the respective aliquots titrated in the manner above 

 described. Together with the titration of those aliquots which had stood 

 for 24 hours before being neutralized the aliquots neutralized on the 

 previous day were retitrated. The alkali thus required was due to the 

 fresh acid which had been formed after the extracts were neutralized 

 These increments are listed in separate columns of the following table. 



Table IV. — Relation between time of extraction and acidity of ice-water extracts of oats 

 and corn, and the formation of fresh acid after neutralization of the extracts ^ 



Time of 

 extrac- 

 tion (in 

 minutes). 



60 



90 



Treatment of extract. 



f Titrated at once 



\Titrated after 24 hours. 



r Titrated at once 



\Titrated after 24 hours. 



fTitrated at once 



\ Titrated after 24 hours. 



Oats. 



First 

 titration. 



0.66 

 •65 



.69 

 .68 



•71 

 .72 



Second 

 titration. 



Com meal. 



First Second 



titration, titration. 



0-73 

 •73 



.86 



•85 



o. 24 



23 



* Expressed in cubic centimeters of Njio sodium hydroxid required to neutralize 25 cc. of extract (3 gm. 

 of material). 



It is seen from the foregoing table that the amount of acid found in 

 the extracts varies with the time of extraction. However, with oats 

 only slight increases in acidity were observed if the extraction period 

 was extended beyond i hour. With corn, the difference between the 

 values for the 60- and 90-minute extractions was rather marked, whereas 

 the difference between the 90- and 120-minute extractions was insig- 

 nificant. 



There are two possible explanations for the slight differences in the 

 quantity of acids found in the three oat extracts of Table IV. One 

 would be that the acids present in the material are dissolved very slowly 



