100 EXPERIMENT STATION RECORD. 



tlie nitrid of magnesium (MgjNo) formed by buruiug- maguesium in air 

 by two methods to contain 20.42 and 26.82 per cent of nitrogen, as com- 

 pared with the theoretical 28 per cent; while the nitrid formed by com- 

 bination with chemical nitrogen contained 27.21 i^er cent of nitrogen. 

 He discnsses the results of Ramsay and Rossel for maguesium nitrid. — 



B. W. KILGOKE. 



Determination of the citrate-soluble phosphoric acid in Thomas 

 slag by direct precipitation of the citrate solution obtained in the 

 Wagner method, W. Hoffmeister [Chem, Ztg., 20 {1890), No. 31, p. 

 305). — To an aliquot part of the citrate solution of 5 gm. of Thomas slag 

 a small amount of concentrated sulphuric acid is added (5 cc. of acid for 

 each gram of slag) and tlie solution evaporated until it is of a thick 

 sirupy consistency and a slightly yellow color. The residue is washed 

 into a measuring flask with hot water and after cooling the flask is filled 

 to the mark with water. The solution is then filtered and an aliquot 

 part of the filtrate corresponding to 0.5 gm. of slag is transferred to a 

 beaker covered with a funnel, 10 cc of fuming nitric acidadded, and the 

 solution heated over a small flame nearly to boiling. After rinsing off the 

 funnel 50 cc. of the ammonium citrate solution ordinarily used in the 

 determination of phosphoric acid is added, the solution cooled, and 

 the phosphoric acid precipitated by means of 10 cc. of magnesia mixture 

 in the presence of sufficient ammonia to neutralize the sulphuric acid 

 and nitric acid present. For complete precipitation it is necessary to 

 allow the solution to stand 12 hours with occasional stirring. 



Rapid estimation of insoluble phosphate, V. Edwards {Chem. 

 News, 73 {1896), p. 25 ; abs. In Jour. Chem. Soc, 1890, Apr., p. 373). — 

 The method j^roposed is as follows: "The residue, from the exhaustion 

 of 0.5 gm.of the substance with cold and hot water, is boiled fin^ a short 

 time in water containing a very small quantity of hydrochloric acid, 

 filtered, nmde up to 300 cc, rendered alkaline with ammonia, and then 

 faintly acidified with acetic acid. The solution is then placed on a sand 

 bath and titrated hot with standard uranium acetate of the strength 

 1 cc. = 0.01 gm. CaiPoOa." 



Investigations on the determination of phosphoric acid, C. 

 Meineke {Chem. Ztg., 20 {1890), No. 13, pp. 107-113).— Tests of 2 

 methods are reported : Determination of phosphoric acid (1) by igniting 

 the yellow molybdic precipitate, proposed by the author in 1885;' and 

 (2) as magnesium pyrophosphate. In addition studies of the influence 

 of ammonium chlorid on the molybdic precipitation of phosphoric acid 

 in solutions rich in iron are reported. 



The molybdic solution used in the first method is prepared as fol- 

 lows: Dissolve 150 gm. of ammonium molybdate in 150 cc. of ammonia 

 of 0.91 specific gravity and 850 cc. of water and stir in 1,000 cc. of 

 nitric acid of 1.2 specific gravity; heat for 10 minutes at 90° C, decant, 

 and filter. The method is carried out as follows: In case of solutions 



'Report Anal. Chem., 5 (1885), p. 153. 



