16 EXPERIMENT STATION RECORD. 



reaction; and (6) the content of arsenic, asli, moisture, and impurities or 

 adulterations. 



The estimation of small quantities of manganese and chromium in min- 

 erals and rocks, M. Dittkich {Ztschr. Anorgan. Chem., 80 (1913), No. 2, pp. 

 171-173; a1)S. in Jour. Chem. Sac. [London], 104 (1913), No. 606, II, pp. 3U, 

 3^5), — It is pointed out that the colorimetric method for manganese Is often 

 difficult to use because of the presence of chromivmi which changes the color 

 of the solution. If, however, ammonia is added to the mixed solution of per- 

 manganate and chromate and the solution is warmed, all of the manganese 

 and iron are precipitated in the hydroxid form. The washed precipitate can 

 then be dissolved and oxidized and the manganese estimated with ammonium 

 persulphate in the usual manner. The chromium can be detei-mined colorimetri- 

 cally by comparing it with a standard solution of potassium chromate after 

 the removal of silver by sodium chlorid and concentrating. The method is not 

 entirely accurate. 



Drying in an electrically heated vacuum desiccator for determining the 

 hygroscopicity of soils, R. Hornberger (Landw. Vers. Stat., 82 (1913), No. 3-Jf, 

 pp. 303-307). — Certain defects are present in the Mitscherlich desiccating appa- 

 ratus. In this article the author relates his experiences with the apparatus 

 and suggests various contrivances for overcoming the difBculties. 



The determination of phosphoric acid in the soil, R. Hornbergee (Landw. 

 Vers. Stat., 82 (1913), No. 3-4, pp. 299-302) .—During the course of analyses of 

 the hydrochloric extract of forest soils (red sandstone) a small part of the 

 phosphomolybdate precipitate did not dissolve in ammonium hydroxid despite 

 the fact that thorough washing was done. This material remained on the filter 

 as a small white residue. The ommoniacal solution of the phosphomolj'bdate 

 was not clear after filtration and after a few days clarification set in with a 

 deposit of some whitish flalies. The deposit was found to consist of titanium. 

 Test, were then made with artificial mixtures to determine how this disturb- 

 ing factor could be removed. It is shown that when molybdic acid solution 

 and ammonium nitrate are added to a nitric acid solution of the phosphate, 

 some titanium is precipitated which remains insoluble when the phosphomolyb- 

 date is treated with ammonium hydroxid. A portion of this, which is present 

 in a fine state, passes through the filter into the filtrate. 



The titanium in the filtrate can be removed after allowing the solution to 

 stand for a time but it is advisable to add to the wash water some ammonium 

 chlorid in order to prevent the titanium from passing through the filter. The 

 total elimination of titanium was not possible, but the least contamination of 

 the ammonium phosphomolybdate precipitate takes place when the molybdate 

 solution is in excess and no hydrochloric acid is present; under these condi- 

 tions the percentage of phosphorus in the titanium precipitate is also the 

 smallest. Both of these errors can be prevented if the titanium residue from 

 the filtrate is fused with soda and the melt is extracted with water. The 

 phosphorus goes into solution, the titanium remains behind, and after driving 

 out the carbon dioxid the phosphoric acid can be determined in the usual 

 manner. 



Citrate-soluble phosphoric acid in. some crude phosphates, M. A. Stabo- 

 DXJBOWA and I. Y. Jakuschkin (7ct. Mosl-ov. Selsk. Khoz. Inst. (Ann. Inst. 

 Agron. Moscou), 19 (1913), No. 2, pp. 377-395) .—This investigation shows that 

 crude phosphates of all kinds can be decomposed with acetic acid. It 

 was furthermore noted that Wagner's reagent also attacks the most internal 

 nucleus of all raw phosphates and consequently is of no value for judging 

 adulterations in Thomas slag powders. Petermann's reagent can not be used, 

 especially at low temperatures, for decomposing crude phosphates which are 



