site hexaphosphate contains water of crystallization corresponding to 

 8 molecules H 2 and the water of crystallization in the heptabarium 

 salt corresponds to 14 molecules H 2 0. These crystalline barium salts 

 are free from inorganic phosphoric acid. However, after standing for 

 several months at room temperature in a well closed bottle a slight 

 reaction for inorganic phosphoric acid will be obtained with ammo- 

 nium molybdate. Drying these salts at 100° likewise causes a slight 

 liberation of free phosphoric acid. 



As intimated above, inosite phosphoric acid generally forms acid 

 salts ; in fact, it is very difficult to obtain any salt of this acid, even 

 from neutral solutions, which does not show an acid reaction on moist 

 litmus paper. The silver salt, for instance, obtained by precipitating 

 a solution of the acid neutralized with ammonia contains only about 

 8 or 7 equivalents of silver and has a strong acid reaction. 



It has been mentioned previously that only one-half of the acid 

 hydroxyls enter readily into reaction with bases. Salts with binary 

 bases, such as barium, contain therefore only 3 atoms of the base when 

 separated from slightly acid solutions. Starkenstein (1911) also men- 

 tions this fact. In titrating the acid with standard uranium acetate 

 he observed that he obtained only one-half the value for phosphorus. 

 These reactive acid hydroxyls are probably adjacent, but linked to dif- 

 ferent phosphoric acid residue, giving salts with binary bases of the 

 following type : 



The salts of inosite phosphoric acid are more soluble in cold than 

 in hot water. This fact was first observed by Palladin (1894) and led 

 to the discovery of the substance in an aqueous extract of senapis 

 niger. Advantage has frequently been taken of this property in iso- 

 lating crude salts of the acid from acidulated aqueous extracts of plant 

 material. The dilute acid extract is heated to boiling. This coagu- 

 lates the proteins and the alkaline earth salts of inosite phosphoric 

 acid are also precipitated, but they redissolve on cooling the liquid. 

 After cooling, the permanent precipitate, consisting of proteins, etc., 

 is filtered off. The filtrate is again heated to boiling and the precipi- 

 tate which then forms represents the crude phytin preparation mixed 

 with some inorganic phosphate. 



Pure salts of inosite phosphoric acid are generally white or color- 



17 



