AGEICULTUKAL CHEMISTRY— AGROTECHNY, 705 



and medical. A chapter is also given in reference to recent bacteriological ap- 

 paratus. 



An iodimetric determination of phosphorus, P. Artmann {Ztschr. Analyt. 

 Chem., Jf9 {1910), ^o. 1, pp. l~2o). — After considering the acidimetric, oxydi- 

 metric, and precipitation methods, the author recommends the following iodi- 

 metric method for phosphorus determination in phosphates: 



One gm. of the substance is dissolved in about 30 cc. of water containing 

 (S to 10 cc. of nitric acid (density 12). and heated up to the boiling point, from 

 2 to 3 cc. of 1 : 1 hydrochloric acid being adde^l during the process. If sulphates 

 are present these are precipitated at the boiling point with barium nitrate. 

 The flask is then filled to the 250 cc. mark and filtered. Twenty-five cc. of the 

 filtrate is taken for the actual determination, there being added to it 4 gm. of 

 ammonium nitrate and 2 cc. of nitric acid, the mixture heated to 40° C, and 

 12 to 15 cc. of ammonium molybdate solution (previously heated up to 40°) 

 added dropwise. Tlie mixture is then stirred for 5 minutes at 40°. and after a 

 lapse of 15 minutes 5 cc. more of the molybdate solution is added. After heat- 

 ing at a temperature of 40° to 45° for from f to 1 hour, the solution is decanted 

 and filtered through a hardened 6 cm. filter with the aid of a filter jnimp and 

 wash water at 14°. The decantation is continued until 5 drops of the filtrate 

 give no definite brown coloration with potassium ferrocyauid. 



The precipitate which has been carried over on the filter is dissolved in 

 one-half normal sodium hydrate and washed into the original beaker with 

 water, the washing being continued as long as an odor of ammonium hydrate 

 is apparent. The precipitate which has remained in the beaker after the de- 

 canting process is dissolved by the aid of from 4 to 5 cc. of double normal 

 sodium hydrate solution. To the solution is added 20 cc. of an allialine bromin 

 solution which has been pi'eviously compared with thiosulphate, from 8 to 10 

 gm. of sodium hydrogen phosphate, and finally 1.5 gm. of potassium iodid. 

 This is acidified with 15 cc. fourth-normal sulphuric acid and titrated back with 

 tenth-noi-mal sodium thiosulphate. For calculating the results the following 

 a /\y p\ 



formula is used : x= Av-i^noo i • ^^ this, a^grams of iodin for 1 cc. of sodium 

 U.UloUoo.d 



thiosulphate solution, b = the number of cubic centimeters of sodium thiosulphate 



which represents 20 cc. of the alkaline bromin solution, c=the number of cubic 



centimeters of tenth-normal thiosulphate employed to titrate back, d=the 



amount of the original substance taken in gi'ams, and x=the percentage of 



phosphoric acid. 



The alkaline bromin solution is prepared by carefully adding 15 cc. of bromin 

 to 1 liter of normal sodium hydroxid solution amid stirring, keeping the sodium 

 hydroxid surroundeJ by ice water during the addition. The solution is diluted 

 once with water upon use. The author in a later work will report on the 

 application of the method to fertilizer and iron analyses. 



Determination of hypophosphoric, phosphorous, and hypophosphorous 

 acids in the presence of each, other and phosphoric acid, A. Rosenheim and 

 J. TiNSKEB {Ztschr. Anorgan. Chem., 6.'i (1909), Xo. >,, pp. 327-3-'fl; abs. in Jour. 

 Soc. Chem. Indus., 28 {1909), No. 2^, p. 1312). — Hypophosphoric acid may be 

 titrated accurately with potassium permanganate solution, and further, reacts 

 quantitatively with uranyl nitrate, gives a yellow precipitate with it, and is not 

 affected by heating the iodin solution. Phosphorous and hypophosphorous acids 

 are oxidized by both iodin and potassium permanganate, but give no precipitate 

 with uranyl nitrate. 



42556— Xo. 8—10 2 



