110 EXPERIMENT STATION EECOED. 



course, in any case calcite wonkl be removed — ii fact which renders very diffi- 

 cult the determination of small quantities of this mineral in discolored soils." 



The strength of nitric acid, period of extraction, and ignition as affecting 

 the gravimetric determination of phosphoric acid in soils, O. L. Braueb 

 (Jour. Indus, and Engin. Cliem., 6 U9Vf), No. 12, pp. 100.',, 1005).— "Acid 

 weaker than 1 N to 2 N HNOs will not extract all the soluble phosphoric acid 

 from a soil. It is needless to extract with the acid for a longer period than 

 two hours on the steam bath. Ignition decreases the HNOs-soluble phosphoric 

 acid in the soils." 



The estimation of citric acid-soluble phosphoric acid in Thomas slag 

 powder, Neubaueb {Landw. Yers. Stat., 85 {19U), No. 3-5, pp. 238-2J,7).—A 

 report by the referee of cooperative work done with the methods for deter- 

 mining citric acid-soluble phosphoric acid given to the Association of Agri- 

 cultural Experiment Stations of Germany. The methods best suited for the 

 purpose, according to the referee, are the iron citrate method (B. S. R., 29, 

 pp. 409, 410) and the Lorenz method (E. S. R., 13, p. 14; 31, p. 112). Preference 

 is given to the latter method. Discussions of the report by members of the 

 Association are included. 



Estimation of water-soluble phosphoric acid in superphosphate mixtures, 

 Netjbaueb (Landw. Vers. Stat., 85 (19U), No. S-5, pp. 2J,8, 2^9).— The author 

 believes that better results are obtainable if the flask containing the sample 

 is filled up to the mark before rotation. This confirms the opinion of Pilz 

 (E. S. R., 30. p. 809). 



About the titrametric estimation of cyanamid, G. Grube and J. Krtjgeb 

 (Ztschr. Angew. Chem., 21 (191J,), No. 46, Aufsatzteil, pp. 326, 327; a6s. in 

 Chem. Ztg., 38 (1914), No. 114-115, Repert., p. .^88).— The authors conclude 

 that the Kappen method (E. S. R., 21, p. 419) and the Caro method (E. S. R., 

 25, p. 24) will yield identical results, provided the precipitation is done with 

 silver nitrate in a slightly acid (acetic) solution of the cyanamid and the 

 solution is subsequently made slightly alkaline with ammonia. A large excess 

 of amnioniacal salt or free ammonia must not be present. 



Examination, sampling, and guaranty of fertilizing lime, Neubauer 

 (Landw. Tcr>i. Stat., 85 (1914), No. 3-5, pp. 228-238). — In cooperative work 

 imder the auspices of the German Association of Agricultural Experiment Sta- 

 tions six limes were studied by the Tacke sulphuric acid titration (official) 

 method, the Forster hydrochloric acid titration method, and the Fresenius 

 method.'* 



The figures obtained by the Fresenius method were much more uniform 

 than those given by the Tacke method and the operation is more simple than 

 the latter method. Both methods, however, can be used only for comparatively 

 pure limes. The method of sampling in use by the association is deemed 

 inadequate. 



Blood charcoal as a purifying agent for arsenic solutions previous to titra- 

 tion, R. M. Chapin (Jour. Indus, and Engin. Chem., 6 (1914), No. 12, pp. 1002, 

 1003). — In assaying arsenical dipping fluids, of which an important ingredient 

 is an alkaline arsenite, it often becomes necessary to remove organic material 

 which interferes with the titration by iodiu. Organic matter, when present, 

 may absorb iodin and thus render the end points inaccurate and fugitive, and 

 it furthermore imparts color to the solution. Purified kaolin or infusorial 

 earth only obviates the disturbing factor moderately, but in blood charcoal a 



» Quantitative Chemical Analysis, by K. R. Fresenius, trans, by A. I. Cohn, 1904, vol. 2, 

 pp. 334, 335. 



