0.2508 gram dry substance gave O.OoOO gram Mg 2 P 2 7 , equiva- 

 lent to 7.73 per cent, phosphorus or 28.30 per cent, of the total phos- 

 phorus was precipitated as inorganic phosphoric acid. 



Before drying: 



0.1889 gram (dry substance calculated) gave 0.0039 gram 

 Mg,P 2 O r , equivalent to 0.57 per cent, of phosphorus or 2.08 per cent. 

 of total phosphorus. 



As will be noticed from the above figures, 26.2 per cent, of the 

 total phosphorus had been hydrolyzed by drying at 105° for about 

 24 hours. 



An old sample of inosite hexaphosphoric acid, which had been 

 kept in the laboratory for about 18 months, was examined in the 

 same manner. It was practically black in color. It lost about 22 per 

 cent, of its weight on drying as above for about 20 hours. After 

 decomposing by the Neumann method it was found to contain 27.08 

 per cent, of phosphorus. 



The dry preparation gave the following : 



0.2348 gram dry substance gave 0.0733 gram Mg 2 P 2 7 , equiva- 

 lent to 8.70 per cent, of phosphorus, or 31.43 per cent, of the total 

 phosphorus was present as inorganic phosphoric acid. 



Before drying: 



0.2651 gram (dry substance calculated) gave 0.0295 gram Mg 2 P 2 7 , 

 equivalent to 3.10 per cent, of phosphorus or 11.19 per cent, of the 

 total phosphorus had been hydrolyzed in about 18 months under ordi- 

 nary room conditions. 



In the above case about 20.2 per cent, of the total phosphorus 

 had been hydrolyzed on drying at 105° for about 20 hours. 



A sample of the pure recrystallized barium inosite hexaphos- 

 phate was examined for inorganic phosphoric acid in the same way. 

 After standing in the laboratory for five or six weeks the following 

 results were obtained : 



After drying at 105° in vacuum over phosphorus pentoxide 0.2108 

 gram substance gave 0.0104 gram Mg 2 P 2 T , equivalent to 1.37 per 

 cent, of phosphorus. 



Before drying: 



0.2060 gram (dry substance calculated) gave 0.0030 gram Mg 2 P,0 7 , 

 equivalent to 0.40 per cent, of phosphorus. 



By drying at 105° the inorganic phosphorus increased about 2Vo 

 times. 



A portion of the inorganic phosphoric acid found in the above 

 determinations was probably due to cleavage of the inosite hexaphos- 

 phoric acid by the dilute nitric acid. Such cleavage appears to take 

 place slowly and uniformly, as shown by the following experiment : 



54 



