314 EXPEEIMENT STATION RECORD. 



Experimental data comparing the method with that of Creydt » are submitted. 

 Other data show that the method is quite accurate in the presence of sucrose and 

 glucose, fructose, invert sugar, lactose, maltose, cellulose, and trehalose. 



A comparison of the methods for the determination of ammonia in soil, 

 B. K. Takasov {Zliur. Opytn. Agron. (Russ. Jour. Expt. Landto.), 15 {19l4)f 

 No. 2, pp. 118-lSS). — A comparison of the methods of Boussinghalt, Schlijsing, 

 and Prianischnikov for the determination of ammonia in soil (E. S. R., 28, p. 

 Ill ; 30, p. 215) has led to the following conclusions: 



The method of Boussinghalt usually gives results which are too high; un- 

 doubtedly since the magnesium oxid acts on the nitrogenous substances of the 

 soil and liberates ammonia. In the method of Schlosing complete removal of 

 the ammonia is only obtained by repeated extractions with hydrochloric acid 

 solution. The action of the hydrochloric acid causes a hydrolysis of the nitrog- 

 enous material in the soil which, on heating with magnesium oxid, liberates 

 ammonia, the amount liberated depending on the time of action and also on 

 the strength of the hydrocliloric acid. The method of Prianischnikov gives 

 more ammonia than that of Schlosing with soils rich in humus; with loamy 

 soils the reverse is true. The results obtained indicate that as yet there Is no 

 reliable method for the determination of ammonia in soils. 



The determination of phosphoric acid in vegetable material and in 

 phosphates, A. Stutzee and W. Haupt {Jour. Landic, 63 {J915), No. 1, pp. 

 46-JtD). — After having experiencetl some difliculty with the Lorenz method 

 (E. S. R., 13, p. 14) for the determination of phosphoric acid, the authors adopted 

 the following procedure: 



Two gra. of the dried material was heated in a Kjeldahl flask with 25 cc. 

 concentrated sulphuric acid and a few drops of mercury until the mixture be- 

 came colorless. The liquid was then diluted and after cooling transferred to 

 a 500 cc. Erlenmeyer fla.sk. Solid ammonium carbonate was added to 

 neutralize the acid, and when it began to dissolve with difliculty a concentrated 

 solution of ammonium carbonate was added until the liquid was neutral or 

 only slightly alkaline, as indicated by Congo red or other suitable indicator. 

 The liquid was then made acid with concentrated nitric acid, filtered if neces- 

 sary, and heated to incipient boiling. After careful stirring 100 cc. of molybdic 

 acid solution was added. 



The precipitate could be filtered after about two hours' standing, using a 

 weighed, perforated crucible, fitted with an asbestos mat. The precipitate was 

 washed with dilute nitric acid or a solution of ammonium nitrate and finally 

 with strong alcohol to remove the water. The crucible and contents were then 

 dried at from 130 to 140° C, and gently ignited over the Bunsen flame until 

 the precipitate became bluish-green in color. After cooling the residue was 

 weighed as molybdic-phosphoric acid anhydrid (24MoO..PjO»), the factor for 

 calculating as phosphorus pcntoxid being 0.03946. 



The same procedure was used in phosphate analysis. 



The iron-citrate method for the determination of citric-acid-soluble phos- 

 phoric acid in Thomas slag, iM. Popp {Die Eisenzitrat-Mcthode zur Bcstim- 

 niung der zitronciisdureloslichcn Phosphorsdure in Thomasmehlcn. Berlin: 

 Paul Parey, 1915, pp. 29, figs. 5). — The author considers briefly the theory and 

 history of tlie iron-citrate method (E. S. R., 32, p. 611). 



In earlier work (E. S. R., 29, p. 409) on the original method of Bottcher and 

 Wagner, who applied it to Thomas slag, it was found that the ammonium- 

 magnesium-phosphate precipitate was contaminated with silicic acid, which 

 caused high results. This difliculty was overcome in two ways: (1) Evaporation 



•Ztschr. Ver. Uubcuz. Ind., 37 (1S87), pp. 153-180. 



