ORGANIC PHOSPHORIC ACID OF RICE 



By Alice R. Thompson', 

 Assislttnt Chemist, Hawaii Agricultural Experiimnl Station 



That phosphoric acid occurs in organic combinations with inosite in 

 the seeds of many plants has been shown by several investigators. 

 Postemak (9),^ Patten and Hart (8), Hart and Andrews (6), Hart and 

 Tottingham (7), Anderson (i, 2, 3, 5), Rather (10, 11), and others have 

 isolated this organic substance from pumpkin seed, beans, wheat, com, 

 oats, and cotton seed. Although they have been unable to obtain it by 

 synthesis and still disagree as to the formula and composition of the 

 acid and its salts, it is generally known as phytin or phytic acid. Suzuki 

 et al. (12, 13) and Anderson believe phytin to be a hexaphosphoric 

 acid ester of inosite, and Anderson has shown that the organic phos- 

 phoric acid in wheat bran differs materially from the acid he has obtained 

 from a number of seeds. 



Phytin is completely hydrolyzed into free phosphoric acid and inosite 

 only with difficulty, as Anderson (4) showed by boiling phytin with con- 

 centrated nitric acid for several hours. 



In the previous determination of phosphoric acid in foliage and grain 

 of rice (Oryza saliva) at the Hawaii Experiment Station (14) several 

 methods were used in oxidizing the organic matter. On boiling the 

 grain with a mixture of nitric and hydrochloric acids (aqua regia) the 

 author noticed that, although the solution soon became colorless, giving 

 the appearance of complete oxidation of organic matter, if boiled to 

 dryness a charred mass remained in the flask. Determinations of phos- 

 phoric acid in the solution (not boiled to dryness) in the case of the 

 rice grain showed about one-third of the total phosphoric acid as found 

 by the Neumann method. The determination of phosphoric acid in the 

 foliage, on the other hand, by either method was about the same. 



It was thought that the reason for this resistance to the action of 

 aqua regia is probably the fact that phosphoric acid occurs in the rice 

 grain as phytin and is therefore not completely hydrolyzed. It was 

 decided, therefore, to give some study to the organic phosphoric acid 

 of rice. 



Suzuki et al. (12, 13) obtained an impure salt of phytic acid from rice 

 by extracting the rice bran with a 0.2 per cent hydrochloric-acid solu- 

 tion and precipitating with alcohol. As Anderson (i, 2, 3, 4, 5) has 

 shown that phytin so prepared would contain the inorganic phosphoric 

 acid of the seed, as well as other impurities, the phosphorus content as 

 shown by the resulting analysis is not that of pure phytin. 



It is therefore of interest to obtain the pure salt of phytic acid from 

 rice. In following the methods of Anderson (1, 2, 3, 4, 5) of purifying 

 the acid by repeated solution in hydrochloric acid and precipitation with 

 barium hydroxid, the author hoped to isolate the pure tribarium salt, 

 but the ease of partial hydrolysis of the substance and the difficulty of 

 eliminating all impurities which may be present, such as other phos- 



* Reference made by number to " Literature cited.'' p. 430. 



Journal of Agricultural Researcll. Vol. Ifl. No. 5 



Dept. of Agriculture. WashiuBton, D. C. Feb. 15. 1915 



B 4 

 (42s) 



