igi2] 'Anton Riclmrd Rose 33 



and not as an impurity, though in view of all the available evidence 

 Neuberg's criticism seems at the present time somewhat justifiable. 

 Starkenstein also refused to accept the simple formula proposed 

 by Posternak and offers the f ollowing : 



HO-^P— OH.HO— C-C— OH.HO— P^OH 



^\ j i /^ 



HO— P— OH. HO— C C— OH.HO— P^H 



o/ 11 \) 



(5) HO— C— C— OH 



HO OH 

 0=P P=( 



/\/\ 

 OH O OH 

 M. W., 714 ; C = 10.985^ ; P = 26.05 



He argues that the phosphoric acid is in the pyro-form^ from the 

 fact that its silver salt is the same color as silver pyro-phosphate, 

 and that its behavior when titrated with Standard uranium acetate 

 Solution is also like that of pyro-phosphoric acid. That it is not 

 combined in the usual form of an ester but held loosely in a complex 

 "addition form," he maintains from the fact that an increase of 

 inosite and inorganic phosphate resulted from heating some of the 

 calcium salt for an hour at ioo° C. These arguments are not alto- 

 gether convincing. Anderson has prepared a silver salt of the ortho- 

 tetra-phosphoric acid ester with inosite and reports it as being white 

 like the pyro-phosphoric acid salt. 



In the quantitative titration of pyrophosphoric acid with a uran- 

 ium acetate Solution, standardized by ortho-phosphate and using fer- 

 rocyanide as indicator, only one half of the phosphorus value is 

 obtained. Starkenstein explains this phenomenon by the assump- 

 tion that one half of the more reactive ions of the phosphoric acid 

 have been removed in the dehydration. Now if two phosphoric- 

 acid groups had formed esters with one polyalcohol, analogous con- 

 ditions would have resulted as far as the ions are concerned, and 

 bivalent ions would be expected to connect the two phosphoric acid 



* That phosphorus occurs in plants in the pyro form may seem stränge to 

 many, but this is not the first time that such an occurrence has been suggested. 

 In 1892 Hardin (5". C. Exp. Sta. Bull., N. S., No. 8) reported his finding both 

 pyro- and meta- phosphate in cottonseed meal, when he sought, in this feeding 

 material, a substance toxic to cattle. 



