186 ^^^ Philippine Journal of Science wis 



extract is hydrolized before precipitation with tannic acid, the 

 curative substance is not then precipitated by the tannic acid, 

 but remains in the filtrate. We did not succeed in isolating any 

 greater amount of the curative base by this method than by 

 Funk's method, doubtless because the former also depends upon 

 the use of barium hydroxide to remove the tannic acid. 



We had further hoped that the method described in experiment 

 46 might yield larger quantities of this curative base, since the 

 excessive use of barium hydroxide in breaking up the precipi- 

 tated phosphotungstates was thereby avoided; but after re- 

 peated attempts we were obliged to abandon this method also, 

 because we found that the greater part of the curative base 

 was lost during the final precipitation with silver nitrate in the 

 presence of baryta. This loss may be caused by the action of 

 the free barium hydroxide which is present during the precipi- 

 tation, or may possibly be caused by the oxidizing action of the 

 traces of free nitric acid remaining when the silver is removed 

 by hydrogen sulphide, and the last traces of barium by sul- 

 phuric acid prior to evaporation. It appeared probable to us 

 that larger yields could be obtained only by devising some 

 method in which a prolonged treatment with barium hydroxide 

 would not be employed. 



In selecting more suitable precipitants, barium acetate was 

 used for the following reasons. Funk believed that the curative 

 substance is a pyrimidine base similar to uracil or thymine, 

 and since pyrimidine bases are found only in nucleic acid it is, 

 therefore, probably a constituent of nucleic acid. Several re- 

 actions which have been obtained with this base strongly confirm 

 this view. Thus, the precipitation by silver nitrate in the pres- 

 ence of barium hydroxide, but not in neutral solution, places 

 this base definitely in the pyrimidine rather than the purine 

 group. The neutral reaction of the free base and its precipita- 

 tion by phosphotungstic acid as a free base as well as in the 

 unhydrolyzed form are in perfect agreement with this theory. 



Now, if this base exists as a constituent of nucleic acid, it 

 should be possible to obtain it from the basic barium nucleinate 

 precipitated by barium acetate from the unhydrolyzed extract 

 previously neutralized with barium hydroxide. 



Accordingly the following experiment was performed: 



Experiment U7. — A quantity of unhydrolyzed extract of rice 

 polishings was carefully neutralized by barium hydroxide. An 

 excess of barium acetate was then added and the precipitate 

 so obtained was broken up or hydrolyzed by treating with 5 per 

 cent sulphuric acid at 60° C. for three hours and filtered. The 



