534 EXPERIMENT STATION RECORD. 



"(8) Magnesia reagent. — Dissolve 13 gm. of magnesium chlorid, M g Cl 2 .6H 2 0, and 

 20 gm. of ammonium chlorid, X11,CI, in about 900 cc. of water, add 50 cc. of strong 

 ammonia water (sp. gr. 0.9) and dilute to 1 liter. One cubic centimeter of this 

 solution will precipitate 3.5 mg. of P 2 5 . 



"(9) Filter paper. — This must be free from silica. Schleicher and SchiilPs No. 589 

 or 590, 7 cm. has been found to be very satisfactory for this colorimetric work." 



The determination of citric-acid-soluble phosphoric acid in Thomas slag, 

 0. Bottcher {Ztschr. Angew. Chem., 17 {1904), No. 29, pp. 988-990).— -The author 

 defends his method against Sorge's criticism (E. S. R., 15, p. 1051), claiming that if 

 the method is carried out as expeditiously as it should be there is no error due to 

 solution of the ammonium-magnesium phosphate. 



The action of water upon the phosphates of calcium, F. K. Cameron and 

 A. Seidell {Jour. Amer. Chem. Soc, 26 {1904), No. 11, pp. 1454-1463).— A series of 

 studies are reported from which "it appears that tricalcium phosphate and mono- 

 calcium phosphate are alike in their conduct toward water in that both are very 

 much hydrolyzed and decomposed. 



"With tricalcium phosphate, former study in this laboratory (E. S. R., 16, p. 222) 

 makes it appear improbable that final equilibrium conditions were Obtained in the 

 work here described, but with the monocalcium phosphate there can be but little 

 doubt that the results here given do represent final conditions, and that it is safe to 

 say that with both tri- and mono-calcium phosphate the amount of decomposition and 

 the concentration of the resulting solution at the temperature employed is dependent 

 upon the proportion of the mass of solid phosphate to the mass of water. 



" Dicalcium phosphate is unlike the mono- and tri-compounds, in that it is, rela- 

 tively speaking, but slightly decomposed by water, and appears to dissolve mainly 

 as such. In other words, it is the only phosphate of calcium which is stable in water 

 under ordinary conditions." 



The gravimetric determination of calcium, E. Kettler {Ztschr. Angew. Chem., 

 17 {1904), No. 21, pp. 685, 686). — The author calls attention to the unreliability of 

 the process of converting calcium oxalate into carbonate or oxid and proposes the 

 use of sulphuric acid to convert the lime into sulphate as a more accurate procedure. 



The gravimetric determination of calcium, O. Bruck {Ztschr. Angew. <'hem., 

 17 {1904), No. 2S, pp. 953, 954). — The author states that the conversion of lime pre- 

 cipitates into sulphate before weighing, as proposed by Kettler, is unnecessary, as 

 accurate results can be obtained by conversion into carbonate by heating with 

 ammonium carbonate. 



The gravimetric determination of calcium, E. Kettler {Ztschr. Angew. Chem., 

 17 {1904), No. 39, pp. 1488, 1489). — The author points out that his conclusions 

 regarding the unreliability of the method of converting lime precipitates (oxalate) 

 into oxid or carbonate by ignition were based upon a series of comparative tests, 

 which are enumerated. 



The determination of potash in soils, A. Levi {Staz. Sper. Agr. Ital., 37 {1904), 

 pp. 595-599; abs. in Chem. Chitbl, 1904, II, No. 17, p. 1255).— A form of the ordinary 

 process is described. 



Improvement of the old Benning's method for determining the clay con- 

 tent of soils, Emmerling {Chem. Ztg., 28 {1904), No. 79, p. 940).— It is stated that 

 the addition of a coloring matter (malachite green or methyl violet) to the solution 

 containing the soil in suspension facilitates the separation of the clay. 



The determination of nitrogen in organic compounds, H. C. Sherman and 

 M. J. Falk {Jour. Amer. Chem. Soc, 26 {1904), No. 11, pp. 1469-1474)— -This article 

 reports the results of comparisons on benzamid, betain hydrochlorid, acetanilid, 

 naphthylamin, diphenylamin, and cinchonin sulphate, of the Kjeldahl-Wilfarth 

 method, with and without potassium permanganate, the Gunning method, and the 



