316 EXPEEIMENT STATION EECOED. 



" Now filter tlirough a dry filter into a dry flask. Pipette out 75 cc. of the 

 filtrate into a small beaker and evaporate almost but not quite to dryness. 

 Dissolve in dilute nitric acid and filter if necessary ; then determine phosphorus 

 in the usual gravimetric way, by precipitation first with acid molybdate solu- 

 tion, later with magnesia mixture, and then burning to the pyrophosphate. 



" The result obtained as above represents 6.25 gm. out of the original 10 gm. 

 of material, and so to reduce to 1-gm. basis multiply by 0.16." 



Analytical results of the determination of phosphorus in vegetable sub- 

 stances, as alfalfa, bluegrass, dried brewer's grains, rice polish, gluten feed, 

 timothy, wheat, and wheat bran, using the above procedure with slight modifi- 

 cations, are submitted. 



The method of R. C. Collison (E. S. R., 28, p. 21) was tested by the authors 

 but proved unsatisfactory. Further consideration was given the method as out- 

 lined above with special attention to (1) the completeness of extraction, (2) 

 the effect of using large amounts of magnesia mixture in the precipitation, (3) 

 the allowing of more time for the precipitation with magnesia mixture, (4) 

 the facilitating -of filtration by the use of the centrifuge, and (5) the use of 

 mechanical means to break up the precipitate in acid-alcohol to insure com- 

 plete solution of the phosphate. Tabular data are given showing the results 

 of these tests. The authors draw the following conclusions from their work on 

 inorganic phosphorus estimation in vegetable substances : 



"A 3-hour extraction with 0.2 per cent hydrochloric acid in water appears to 

 accomplish practically complete solution of the inorganic phosphates of finely 

 ground vegetable substances, but in the case of wheat middlings was shown to 

 allow enzymatic hydrolysis of organic phosphorus, with the liberation of inor- 

 ganic phosphate. The Introduction of filter paper pulp into such an extract 

 materially assists in the maintenance of an easily penetrable condition in a 

 magnesia mixture precipitate from the same. It was found possible completely 

 to recover phosphates from filter paper pulp alone as used in this work. 



"The use of the centrifuge very gi-eatly facilitat'S the filtration of dilute 

 nqueous-acid extracts of vege able substances. 



" There has appeared no reason to doubt the completeness of the precipita- 

 tion of the inorganic phosphate.-^ from the 0.2 per cent hydrochloric acid 

 solution, through the use of magnesia mixture and ammonia. 



" The separation of the inorganic phosphates from the phytin and other 

 constituents of the magnesia mixture precipitate, through the agency of 0.2 

 per cent nitric acid in 95 per cent alcohol, is attended by difficulties which have 

 not yet been overcome. That these difficulties are largely physical, as deter- 

 mined by the bulky and often gummy nature of the magiiesia mixture precipi- 

 tate, seems to be a fact. That they are in part of a chemical nature, and due 

 to the cleavage of phytin or other organic phosphorus compounds of the 

 magnesia mixture precipitate through the agency of enzyras, appears also to 

 be true. 



"The use of phenol (50 gm. per liter) in the extractive reagent was shown 

 not to affect the precipitation and estimation of pho.sphates in pure solutions. 

 In the estimation of inorganic phosphorus in extracts of vegetable substances 

 the presence of phenol appeared to favor the recovery of added phosphates. 

 Phenol, when used in this way, sometimes increased but more commonly 

 decreased the inorganic phosphorus. In extracts of certain vegetable products 

 the presence of phenol increased the difficulty, rather commonly experienced, 

 in breaking up the magnesia mixture precipitate in acid alcohol. 



" Modification of the acid-alcohol method of Forbes and associates by the In- 

 troduction of filter paper pulp into the extract from which the phosphates arc 

 to be precipitated, the use of excessive amounts of magnesia mixture in this 



