370 EXPERIMENT STATION RECORD. 



Comparative tests of this method and of the gravimetric method on 

 20 samples gave the following average results: Volumetric method, 

 21.36 percent; gravimetric method, 21.20 percent. An attempt was 

 made to apply this method to the determination of total phosphoric 

 acid. While the average results agree closely with those obtained by 

 the gravimetric method, individual results are somewhat irregular, and 

 in -other respects the method appeared to possess no advantages over 

 the usual methods. 



Determination of the citrate-soluble phosphoric acid in Thomas 

 slag and untreated phosphates, I*. Waciner {Chem. Ztg., 18 {1894), 

 No. 01, pp. 1153, 1154; ab.s. in Analyst, 1894, Sept., pp. 305, 200). — On 

 account of the wide variations in the results of Held experiments with 

 different samples of slag, the author insists on the necessity of a 

 guaranty of solubility of the ])hosphoric acid. Two methods of deter- 

 mining the solubility of the i)hosphoric acid in acid ammonium citrate 

 sohition are proposed. In the first, which is considered the more 

 accurate, the basicity of the slag is determined and neutralized with 

 citric acid previous to treatment with citrate solution. 



The basicity is determined as follows : 



"Five grams of the slag is introduced into a 500 cc. flask, which is then filled up 

 to the marlc with a 1 per cent solution of citric acid and shalcen for half an liour 

 in a Jisiger; 50 cc. of the filtered liquid is then titrated with a one fourth normal 

 soda solution, phenolphthalein being the indicator. 



" For the actual analysis, 5 gm. of the sample is placed in a 500 cc. flask with 200 cc. 

 of water, and there are successively added (1) the quantity of 5 per cent citric acid 

 solution previously found to be necessary to neutralize the slag, (2) 2U0 cc of acid 

 ammonium citrate solution (see below), and (.3) water to the mark. The mixture is 

 shaken in a jigger for half an hour and filtered; to 50 cc. of the filtrate 100 c(^ of 

 molyljdic' solution (see below) is added; the li([uid is heated to 80- C, and after 

 cooling the precii)itate is filtered and treated as usual. 



"The amraoniimi citrate solution is made by dissolving 160 gm. of citric acid and 

 ammonia, equivalent to 28 gm. of nitrogen, in a liter of water, The molybdic solu- 

 tion is'prepared by dissolving 125 gm. of molybdic acid in a slight excess of 2 5 per 

 cent ammonia solution, adding 400 gm. of ammonium nitrate, diluting to 1 liter, and 

 pouring the solution into 1 liter of nitric acid (1.19 sp. gr.). After having been 

 allowed to remain at 35^' C. for 21 hours the solution is filtered." 



If it is desirable to save time the determination of the basicity may 

 be omitted and a citrate solution containing loO gm. of citric acid and 

 ammonia, equivalent to 23 gm. of nitrogen, may be used, but the results 

 are less accurate than those furnished by the first method. 



A new method of determining potash, H. Schweitzer and E. 

 LuNGWiTZ {Chem. ZU/., 18 {1894), No. 09, pp. 1320-1322).— In previous 

 articles' one of the authors has called attention to the inaccuracy of 

 the Lindo-Gladding method, and in the present article the results are 

 given of efforts to devise a method which should be as accurate as the 

 original Fresenius method but easier of manipulation. The essential 

 features of this method are ])recii)itation of the alkaline earths by 



' Chem. Ztg., 16 (1892), p. 1720 (E. S. R., 4, p. 584), 17 (1893), p. 101. 



