RECENT WORK IN A(;RICULTULVL SCIENCE 



AGRICULTURAL CHEMISTRY. 



On methods of determining phosphoric acid in artificial fertilizers, P. 

 Christenskn Cridsxkr. Laiidokononi., I'JUd, No. 5, p/J. S08-S12). — This is a 

 resumf^ of a monograph by the author on the subject. 



The results of determinations of water-sohible phosphoric acid in the same 

 superpliosphates were found to differ as much as 0.75 per cent according to the 

 modifications of the molybdate method proposed by Fresenius, Wagner, and 

 Maercker. Similar differences were found in the results for citrate-soluble 

 phosphoric acid in Thomas slag, and in the case of total phosphoric acid- in bone 

 meal differences of 1 per cent or more were obtained by the various methods. 

 The dift"erences were shown to depend on the manner of precipitating with mag- 

 nesia mixture, and a method of pi'ocedure was worked out by the author which 

 gave correct results. A rapid " direct molybdate " method is recommended for 

 further trial. The yellow precipitate formed by addition of ammonium 

 molybdate is ignited to constant weight, and the residue weighed for calcula- 

 tion of the per cent of phosphoric acid in the fertilizer. The methods are not 

 described. 



The author found that bone meal containing 31 per cent total phosphoric acid 

 gave 30 per cent of phosphoric acid soluble in a 2 per cent citric-acid solution. 

 Its citrate solubility was therefore equal to that of Thomas slag. It follows 

 that phosphoric acid in bone meal must either be equal to that of Thomas slag 

 or, if experience and exact culture trials show it to be less valuable, the present 

 method of valuation of phosphoric acid in Thomas slag can not be considered 

 reliable. — f. w. woll. 



On the rapid analysis of superphosphates, M. .Iacquet, G. Quintanilla, 

 and F. Arreuonijo (Rcr. R. Acad. Cicii. Madrid, Jf (1906), No. 5, pp. 092-598).— 

 The method pi'oposed is as follows : Grind 2.5 gm. of the superphosphate in a 

 mortar with about 15 cc. of cold distilled water, filtering the extract and repeat- 

 ing the operation until the filti'ate amounts to about 200 cc, finally washing the 

 filter with water at 80° C. After cooling add 1 or 2 cc. of nitric or hydrochloric 

 acid to clear up the solution. Digest the filter and contents in 100 cc. of 

 Joulie's citrate solution (400 gm. citric acid per liter) at 60° C. on a water bath 

 for 3 hours, stirring for 1 or 2 minutes every quarter of an hour. Make the so- 

 lution to 250 cc. To 50 cc. portions of the water and citrate solutions add 

 100 cc. of 22° ammonia and 10 to 15 cc. of magnesia mixture (.55MgCl,+105 

 NII^C1+.3.50XH3 of 22° + H,0 to one liter). Shake in a mechanical agitator 

 making 40 to 50 revolutions per minute for 3 hours, collect the precipitate on a 

 filter, and proceed as usual. This method gave resiilts with a variety of 

 materials closely agreeing with those obtained by the ordinary method. In- 

 creasing the revolutions of the shaker to 70 to 80 per minute and reducing the 

 time to 1 hour gave higher results than those yielded liy the ordinary method. 



Investigations on the causes of error in the application of the citro- 



1,3087— No. 4-=-0f! m 2 307 



