This agrees with a dimethyl ester of inosite hexaphosphoric acid. 

 For C H 10 O 24 P 6 (CH 3 ) 2 = 688. 

 Calculated : C=13.95 ; H=3.19 per cent. 



THE WATER-INSOLUBLE SUBSTANCE WHICH SEPARATES 

 FROM INOSITE HEXAPHOSPHORIC ACID AFTER 



DRYING 



As has been mentioned earlier, inosite hexaphosphoric acid, which 

 has been dried to constant weight in vacuum over phosphorus pen- 

 toxide, is not completely soluble in_ water. We have observed this 

 insoluble substance in many instances after drying the acid at 60°, at 

 78° and at 105°. It always separates, on adding water to the dry sub- 

 stance, in thin gelatinous plates. It appears to be practically insolu- 

 ble in hot or cold water. Continued boiling in acidulated water is 

 necessary to dissolve it. It is also insoluble in alcohol and ether. 



In order to obtain some knowledge of the composition of this 

 insoluble substance 2.7 grams of the acid, containing about 12 per 

 cent, of moisture, were dried to constant weight at 105° in vacuum 

 over phosphorus pentoxide. After treating with water the insoluble 

 portion was filtered, washed thoroughly in water and finally in alcohol 

 and ether and dried in vacuum over sulfuric acid. It was then obtained 

 as a dirty, gray powder which weighed 0.23 gram. It was non-hygro- 

 scopic. For analysis it was dried at 105° in vacuum over phosphorus 

 pentoxide at which no change in color was noticeable. The substance 

 was burned with copper oxide and the phosphorus determined in the 

 ash. 



0.2118 gram dry substance gave 0.0569 gram H 2 and 0.1357 gm. 

 CO, and 0.1822 gm. Mg 2 P 2 O r . 



Found : C = 17.47 ; H = 3.00 ; P = 23.98 per cent. 



The quantity of the substance obtained was so small that it was 

 only sufficient for one analysis. Of course, we are unable to state 

 whether it was homogeneous or not, but the analytical results agree 

 approximately with inosite triphosphoric acid minus one molecule of 

 water. The substance may therefore be a partial pyrophosphoric acid 

 ester of inosite or it may represent some complex decomposition pro- 

 duct of inosite hexaphosphoric acid. 



SUMMARY 



The evidence from experimental work shows that the organic 

 phosphorus compound known as phytin or inosite phosphoric acid 

 corresponds in composition to inosite hexaphosphoric acid, C 6 H 18 O 24 P 

 orC a H e O,. (PO(OH) 2 )„. 



62 



