504 EXPERIMENT STATION RECORD. [Vol.43 



sodium peroxid to convei't the organically combined bromin Into broniids and 

 then in sulphuric acid solution with potassium permanganate to liberate the 

 bromin. 



Tke bromin set free is led into a flask containing a definite volume of a 0.1 

 per cent fuchsin solution decolorized by sulphurous acid. The amount of 

 bromin is determined by matching the violet color produced in the reagent with 

 standards of gentian violet, methylene blue, or fuchsin. 



It is stated that with this method 0.2 mg. of bromin in 50 gm. of animal 

 organs can be estimated with accuracy. 



Note on the solubility of benzidin sulphate in water, C. S. Bisson and 

 A. W. Christie (Jour. Indus, and Enyin. Chem., 12 {1920), No. 5, pp. .'f85, JfS6). — 

 The solubility of benzidin sulphate at different temperatures has been deter- 

 mined by agitating an excess of the purified salt with distilled water in a con- 

 stant temperature thermostat, and eitlier evaporating a measured volume of 

 100 or 200 cc. to dryness in a platinum dish on the steam bath, drying at 100° C, 

 cooling in a desiccator, and weighing, or by titrating a measured volume of the 

 solution with n/20 potassium permanganate after the addition of 5 per cent 

 of sulphuric acid. 



The two methods gave concordant results at all temperatures except 80°, tliB 

 solubility increasing from 0.049 and 0.04S gm. per liter at 0° C. to 0.141 and 

 0.149 gm. at 50° as determined by the gravimetric and volumetric methods, 

 respectively. These results are thought to indicate the necessity of using a 

 minimum amount of cold water in washing the benzidin sulphate in quantita- 

 tive determinations of sulphate. 



Chemical soil analysis, P. Mxjntee {Landw. Vers. Sta., 9Jf {1919), No. S-4, 

 pp. 18 1-1 S9).— Thin is a study of the efficacy of various concentrations of hydro- 

 chloric acid at different temperatures as solvents for silica, Iron, aluminum, 

 potash, and phosphoric acid in soils. 



The best results in general were obtained with the digestion of the soils in the 

 cold with concentrated HCl (25 to 30 per cent). Hot concentrated HCl gave 

 slightly better results for potash and phosphoric acid. 



As a general method of extraction the author recommends that 300 gm. of 

 the sample be mixed with 900 cc. of concentrated HCl and shaken occasionally 

 for 48 hours. The solution is then decanted and filtered and 300 cc. of the 

 filtrate evaporated with ammonium chlorid on a water bath. 



A protein color reaction, S. Edlracher {Hoppe-Seylcr's Ztschr. Physiol. 

 Chem., 105 {1919), No. 5-6, pp. 240, 2Jfl).— On shaking a protein solution with 

 sodium hydroxid and dimethyl sulphate until the latter is decomposed, and 

 then adding concentrated sulphuric acid to form a layer at the bottom of the 

 tube, a bluish red color zone is said to form at the juncture of the two liquids. 

 The color is caused by tryptophan and resembles somewhat the glyoxylic re- 

 action for tryptophan. The test is considered to be more delicate than the 

 bromin test for free tryptophan. 



The esteriflcation of alpha amino acids, H. A. Shonle and H. H. Mitchell 

 {Jonr. Amer. Chem. Soc, 42 {1920), No. 6, pp. 1265-1277).— The authors discuss 

 the methods which have so far been used in following the rate of esteriflcation 

 in the analysis of proteins, and describe experimental work leading to a satis- 

 factory modification of the titrimetric method which invoh'cs the use of the 

 Sorensen formaldehyde titration of amino acids. 



In the method as finally adopted, the free amino acid acidity in samples with- 

 drawn from the esterification flask is titrated together with the free mineral 

 acid acidity after the destruction of the amino groups and ammonium salts 

 with formaldehyde. The determination of the free and combined HCl (the 

 only mineral acid present) is obtained by a Volhard chlorin titration, and the 



