110 EXPERIMENT STATION EECOED. 



The residue is talven up with 1 drop of a concentrated sodium carbonate 

 solution, free from potassium, and a few cubic centimeters of warm water. 

 The solution is evaporated and the residue heated until fusion of the sodium 

 carbonate has taken iilace. The cooled residue is approximately neutralized 

 with nitric acid, and any free acid which remains must be removed by evapora- 

 tion. The residue from this is then dissolved in about 5 cc. of hot water and 

 treated with 3 cc. of a 10 per cent cobalt chlorid solution and about 5 cc. of a 

 10 per cent sodium nitrite solution. After this the solution is evaporated to 

 dryness slowly (shaking occasionally during the process to avoid crust forma- 

 tion) at a temperature of from 80 to 90° C, and when cooled 3 cc. of a 10 

 per cent acetic acid is added to dissolve the excess of sodium cobaltic nitrite. 



On solution of the crust 10 cc. of water is added, and the crystalline residue 

 which remains is transferred to a Gooch crucible which holds a disc of hardened 

 filter paper. The precipitate on the filter is washed with small amounts of a 

 2i per cent solution of sodium sulphate. To the crucible and washed residue 

 contained in a beaker about 20 cc. of fiftieth-normal potassium permanganate 

 and 100 cc. of water are added, and the beaker and its contents is placed in a 

 water bath, the temperature of which is then gradually raised to the boiling 

 point. The beaker is shaken occasionally during the interim. If manganese 

 superoxid separates out, 25 cc. of dilute sulphuric acid is added drop-wise. 

 AVhen the yellow precipitate on the filter has dissolved the beaker is removed 

 from the water bath and an excess of fiftieth-normal oxalic acid solution is 

 added, and the excess of oxalic acid is titrated with fiftieth-normal potassium 

 permanganate solution (1 cc.=0.0001571 gm. of potassium oxid). 



This method can also be used for examining material containing large quanti- 

 ties of potassium. 



An improved Hollemann method for estimating phosphoric acid, E. 

 ViTORiA (Chcm. Zlg., 35 (1911), No. 123, p. 1152; abs. in Analyst, 36 (1911), 

 Ko. Jf29, p. 605). — "When a superphosphate is boiled for a few hours in a cold 

 saturated solution of ammonium nitrate, almost the whole of the phosphoric 

 acid goes into solution. About 2 gm. of the supen)hosphate, finely ground and 

 dried at 115 to 120° C, are vigorously boiled for about 10 hours with 100 to 150 

 cc. of ammonium nitrate solution, 10 cc. of sodium acetate solution, and 500 

 cc. of water; the water lost hy evaporation is replaced from time to time, and 

 the liquid is finally made up to 1 liter. Forty cc. of this solution are made 

 slightly alkaline with sodium hydroxid and shaken with 20 cc. of tenth-normal 

 silver nitrate solution; the silver phosphate is filtered off rapidly, and the ex- 

 cess of silver in the filtrate is titrated according to Volhard's method." 



Neutral ammonium citrate solutions, A. J. Patten and C. S. Robinson 

 (Michigan Sfa. Rpf. 1911, pp. 173-178, figs. 2). — The work here reported has 

 been previously noted (E. S. R., 26, p. 98). See also an article by Hall (E. S. R., 

 26, p. 109). 



The use of Busch's " nitron " for the determination of nitrate nitrogen in 

 soils and fertilizers, C. S. Robinson and O. B. Winter (MicJiigan 8ta. Rpt. 

 1911, pp. 178-181). — ^The authors conclude that "the 'nitron' method [E. S. R., 

 16. p. 945] seems to be generally inapplicable to the determination of nitrate 

 nitrogen in soils but can be used to advantage in the determination of this 

 form of nitrogen in fertilizers. The reason for its failure in the case of soils 

 is the presence of organic matter which either contaminates the precipitate 

 or holds it up." 



Practical hijits for determining the hygroscopicity of soils by the Rode- 

 wald-Mitscherlich method, G. von Romberg (Landw. Vers. Stat., 75 {1911), 

 No. 5-6, pp. 488, 4S-4). — This deals with some points in regard to the evacua- 



