1917] AGRICULTURAL CHEMISTRY — AGROTECHNY. 317 



presence of all the ammonia as salts, since the free ammonia is absorbed by 

 charcoal. Analytical data submitted indicate that the new procedure is abso- 

 lutely reliable. 



IV. Urea in urine (501-503). — In the procedure described the urea is decom- 

 posed in the usual manner by urease, and after removal of the urease materials 

 with metaphosphoric acid and treatment with blood charcoal the filtrate is 

 nesslerized and the ammonia determined as usual. Comparative analytical 

 data submitted indicate the accuracy of the procedure. 



V. Urea in blood (pp. 505, 506). — The method described is e.ssentially the 

 same as that used in the determination of urea in urine. 



Estimation of calcium in ash of forage plants and animal carcasses, S. B. 

 KuziEiAN {Jour. Amer. Chem. Soc, 38 {1916), No. 10, pp. 1996-2000). — A rapid 

 and accurate modified procedure is described by the author, at the Iowa Ex- 

 periment Station, which consists essentially in removing the phosphorus as 

 phosphomolybdate from an acid solution of the ash and precipitation of the 

 calcium from the filtrate as calcium oxalate, either directly or after the re- 

 moval of the excess of molybdenum as sulphid. No advantage was found, how- 

 ever, in the latter process. 



Advantages claimed for the procedure as compared to the official basic acetate 

 method (E. S. R., 20, p. 512) are that it yields more accurate and concordant 

 results ; no attention need be given to the maintenance of exact neutrality of 

 the solution ; the volume of the filtrate resulting from the precipitation of phos- 

 phorus can be kept reasonably small, so that no evaporation is necessary ; the 

 time required for the determination is greatly shortened ; and phosphorus and 

 calcium may be determined in the same" aliquot. 



The method outlined by Shedd (E. S.'*R.,'27, p. 616) has been found to yield 

 excellent results with slight modifications, which consist essentially in boiling 

 the calcium oxalate precipitate for 30 minutes on a hot plate, filtering through 

 a Gooch crucible, and igniting to convert the oxalates into oxids instead of dis- 

 solving the precipitate with hydrochloric acid and reprecipitating with dilute 

 ammonia, which operation seems to be insufficient to remove completely ad- 

 hering traces of molybdenum. The ignited residue is then dissolved in dilute 

 hydrochloric acid, filtered, ammonium chlorid and ammonia added, and the 

 liquid boiled until the odor of ammonia is faint. The precipitated iron and 

 aluminum are removed and the calcium precipitated as oxalate. 



Modification of the Pratt method for the determination of citric acid, J. J. 

 WiLLAMAN {Jour. Amer. Chem. Soc., 38 {1916), No. 10, pp. 2193-2199). — After 

 a thorough study of the various steps in the method described by Pratt (E. S. 

 R., 26, p. 509) the following modified method is outlined: 



The pectins in the fruit juice or other plant material are precipitated by two 

 volumes of 50 per cent alcohol, and the precipitate, after settling, filtered 

 through filter paper on a Biichner funnel and washed twice with 65 per cent 

 alcohol. The filtrate is diluted with water to give approximately a 30 per 

 cent alcohol content by volume, and 5 cc. of barium acetate solution then 

 added. The barium citrate is filtered through asbestos in a Gooch crucible, 

 washed with 30 per cent alcohol, and dried in a water oven. The precipitate 

 is dissolved in hot 6 per cent phosphoric acid solution, using three portions of 

 20 cc. each and followed by hot water. The filtrate and washings (which 

 should be about 100 cc. in volume) are transferred to the oxidation flask, a 

 piece of glass tubing or glass beads added, if necessary, to prevent bumping, 

 and the solution oxidized with potassium permanganate as described in the 

 original method. The adapter of the condenser dips into 40 cc. of Deniges' 

 solution contained iu u 500 cc. Erleumeyer flask. After the oxidation is com- 



