ON THE PHOSPHORUS CONTENT OF STARCH* 



A. W. THOMAS 



(Biochemtcal Laboratory of Columbia University, at the College of Physicians 



and Surgeons, New York.) 



The fact that starch contains phosphorus has been known for a 

 long time but, stränge to say, very little work has been done to 

 determine the relation of the phosphorus to the starch. 



Fouard,^ while studying the colloidal properties of starch, made 

 some interesting determinations of its phosphorus content. He 

 made soluble starch f rom raw starch by the Lintner process : this he 

 called No. i ; and, by acid treatment of this portion, he made a 

 second preparation of soluble starch : No. 2 ; and so on until, by suc- 

 cessive acid treatments, he had five specimens of soluble starch. All 

 were washed free from acid. He incinerated portions of each and 

 determined the phosphoric anhydrid in the ash. Starting with a 

 starch whose phosphorus content was 0.0724 percent, his fifth puri- 

 fied sample contained 0.0422 per cent. He reported the following 

 results : 



Initial starch 



Soluble starch i 



Percent of ash . . . 

 Percent of H3PO4 



0.3310 

 0.191S 



0.1950 

 0.1318 



0.171S 

 0.1177 



0.1450 

 0.1148 



0.1260 

 0.1210 



0.1240 

 0.1117 



It is interesting to note that in the purest sample the ash con- 

 sisted almost wholly of phosphoric acid, but that, as the starch be- 

 came purer, the percentage of ash decreased from 0.331 percent to 

 0.124 percent while the phosphoric acid decreased only from 0.19 15 

 percent to 0.1117 percent. This seems to indicate that the phos- 

 phorus was present in chemical combination with the starch. 

 Fouard, however, does not believe this to be the case. He made 

 titrations of the total acidity toward methyl orange and phenol- 



* Proceedings of the Columbia Univ. Biochem. Assoc. (i6th meeting, Feb. 6, 

 1914). 



1 Fouard : Compt. rend., 1907, cxliv, p. 501. 



403 



