AGEICULTURAL CHEMISTRY AGEOTECHNY. Ill 



substance was found which, when used in small amounts and with brief diges- 

 tion produced filtrates wherein the end point came out sharply and perma- 

 nently. Blood charcoal, thoiigh slightly absorbing arsenic acid from acid 

 solution, will again release it quantitatively, but more or less oxidized to 

 arsenic acid. When the charcoal is washed this finding may be of considerable 

 A'alue in the determination of both arsenious and arsenic acid in a variety of 

 substances. A test w.is made of its decolorizing power on a sample of London 

 purple with good results. 



See also a previous note (E. S. R., 31, p. 11.'')). 



A substitute for potassium pennanganate to liberate foi-maldehyde gas 

 from, a water solution, S. G. Dixon {Jour. Amer. Med. Assoc, 64 {1915), No. 

 5, p. 4-'^9). — The formaldehyde solution shipped in combination with sulphuric 

 acid when exiwsed to extremely low temperatures in winter was not found 

 sufficiently stable for northern climates. By adding 1^ fluid oz. of glycerin 

 to the formula a solution was obtained which is moderately stable at low 

 temperature and will withstand polymerization. The following formula is 

 now used: "Sodium dichromate, 10 oz. avoirdupois; saturated solution of 

 formaldehyde gas, 1 pint; sulphuric acid, commercial, IJ fluid oz. ; glycerin, 

 14 fluid oz." 



It was also found that when the acidulated solution became cloudy on ac- 

 count of low temperatures it could be made clear and potent by gently warm- 

 ing it for a long period of time. 



See also a previous note (E. S. R., 3.3, p. 12). 



An improved method for the estimation of inorganic phosphoric acid in 

 certain tissues and food products, R. M. Chapin and W. C. PowiCK (Jour. 

 Biol. Chem., 20 {1915), No. 2, pp. 97-11-',).— The method, which was designed 

 for and effectively used in the determination of inorganic phosphorus in eggs 

 and in meats, is said to possess a sufficient number of advantages to make it 

 superior to the methods of Emmett and Grindley (E. S. R., 17, p. 887), Sieg- 

 fried and Singewald (E. S. R., 17, p. G35), and Forbes et al. (E. S. R., 23, 

 p. 303). "The Emmett and Grindley method falls short by the use of a 

 neutral solvent and of heat; the Siegfried and Singewald method, by failure 

 to remove the protective colloids, by exposure of the organic phosphorus to th^-^ 

 action of the phosphate precipitant, and by the long duration of the initial 

 filtration ; and the Forbes method, by the use of heat and the necessity for a 

 double filtration. Finally, Collison's modification of the Forbes method of 

 extraction is open to the criticism that the proteid superficially coagulated by 

 the strong alcohol interferes with the further penetration of the tissue by the 

 solvent." 



In the method proposed picric acid solution containing a small amount of 

 hydrochloric acid is used for extractijig the phosphorus. " The extraction Is 

 complete ; bacterial action is prevented, and the proteids are effectually coagu- 

 lated by the reagent, while the danger of chemical or enzymatic changes is 

 minimized by the low temperature and the rapidity of the extraction. The 

 extract is easily filtered and is practically free from organically combined 

 phosphorus, while by the use of an aliquot of the filtrate for further work, a 

 tedious washing of the precipitate is avoided." 



In the method an initial px-ecipitation is made with magnesia mixture and 

 the final precipitation by means of an ammonium molybdate. The phosphoric 

 acid is finally estimated gravimetrically by weighing the ammonium phospho- 

 molybdate by the Lorenz method (E. S. R., 13, p. 14) as modified by jSTeubauer 

 and Liicker (E. S. R., 27, p. 503). Several modifications of the method are 

 also presented. 



