404 Phosphorus Content of Starch [April-July 



phthalein indicators : and, due to a rough difference in the titrations 

 with the two indicators (the difference was not constant), he claimed 

 that the phosphorus was present in the form of phosphoric acid. 

 He Said that if it were in organic combination no acid reaction 

 would be manifested. 



Ford,^ in the course of diastase studies, attempted to free starch 

 f rom " phosphates," by reprecipitating several times f rom acid Solu- 

 tion by means of alcohol. He found, however, that he could not 

 entirely remove the phosphorus Compound, his purest preparation of 

 starch containing o.i percent phosphoric anhydrid. The aqueous 

 Solution of this starch was neutral to rosolic acid and methyl orange. 



Now, if Fouard's view that phosphorus is present in starch as 

 free phosphoric acid is true, why can it not be washed out ? Why, 

 in his own purification experiments, did the gross weight of ash 

 decrease 62 percent while the phosphoric acid (determined in the 

 ash) decreased only 41 percent? Surely, if starch is not combined 

 chemically with the phosphorus, its hold in the preparations is aston- 

 ishingly tenacious. 



Purification experiments conducted in this laboratory confirm 

 Ford's and Fouard's experiences in that it is impossible to free 

 starch entirely from phosphorus. ^ 



On Oct. 27 twelve medium sized potatoes were macerated, the 

 starch separated and kept under water and toluene until Nov. 3, 

 when starch from twenty-four freshly macerated potatoes was added 

 to the first portion. The starch was washed by decantation and 

 shaking with 4-5 liters of hydrant water several times each day 

 until Nov. 10. On Nov. 10 the product was dried between filter 

 papers in the draught of an electric fan until Nov. 11 (Sample A), 

 when 490 gm. were placed in 5 liters of 7 percent hydrochloric acid 

 sol. and shaken vigorously in order to convert the raw starch to sol- 

 uble starch. This shaking was repeated twice daily until Nov. 18, 

 when the acid sol. was poured off and dist. water was substituted for 

 it. Fresh dist. water was added daily, and by Nov. 25 the wash- 

 ings were neutral to litmus (Sample B). From Nov. 25 to Dec. 15 

 (taking Sample C on Dec. i and Sample D on Dec. 8) the starch 

 was washed by decantation and shaking with 2 liters of dist. water 

 twice daily. 



2 Ford : Jour. Soc. Chem. Ind., 1904, xxiii, p. 414. 



