AGRICULTURAL CHEMISTRY — AGROTECHNY. 811 



cose and almoud trinitril glucosid, and amygdalinase, which fnrther splits the 

 almond trinitril glucosid into benzaldehyde, glucose, and hydrocyanic acid. 



Note on Kjeldahl's process, V. Edwards and D. Chads (Cfieni. News, 103 

 (1911), No. 2G7S, p. 138; abs. in Jour. Soc. Chem. Indus., 30 (1911), No. 7, p. 

 451). — If granulated tin Is used instead of granulated zinc to prevent bumping, 

 very little frothing is produced. 



New method of determining nitrites, E. Rupp and F. Lehmann (Arch. 

 PJiarm., 2^9 (1011), No. 3, pp. 214-211; ahs. in Pharm. Jour. [London], 4. ser., 

 32 (1911), No. 2485, p. I4I; Merck's Rpt., 20 (1911), No. 8, p. 232).— The 

 method proposed rests on the fact that nitrous acid is oxidized quantitatively 

 by bromin to nitric acid. 



The estimation of small quantities of mang'anese, especially in the ash of 

 plants or of animal organs, G. Bektband (Bui. Hoc. Chim. France, 4- ser., 9 

 (1911), No. 8, pp. 361-370; Ann. Chim. Analyt., 16 (1911), No. 8, pp. 285-294; 

 abs. in Analyst, 36 (1911), No. 424, pp. 369, 370).— The material under exami- 

 nation is incinerated at a dull red heat until all the carbon is apparently burned 

 off. The ash after cooling is moistened with hydrochloric acid and placed on a 

 water bath. A little sulphuric acid is added, the mixtui'e evaporated to di-yness, 

 and the contents of the dish again heated at a red heat. The manganese is then 

 estimated in the ash by the persulphate method (colorimetrically), in the 

 presence of silver nitrate as follows: 



" Dissolve the plant ashes in 10 cc. of nitric acid (specific gravity l.OS), add 5 

 drops of a 10 per cent solution of siher nitrate, and at least 0.1 gm. of potassium 

 persulphate. . . . The mixture is heated gently until the pink color shows no 

 further increase in intensity. The temperature is then raised to boiling to 

 destroy the excess of persulphate, and maintained at the boiling temperature 

 until oxygen ceases to be evolved. The cooled liquid is made up to exactly 10 

 cc, and its color matched by that of a standard solution of manganese sulphate 

 which has been oxidized in a similar manner." 



A modifi^ed procedure for the detection of silicates, fluorids, and fluosilicates, 

 P. E. Browning (Amcr. Jour. Sci., 4. ser., 32 (1911), No. 190, pp. 249, 250). — 

 As the usual methods for detecting silica and fluorin often yield unsatisfactory 

 results in the hands of inexperienced persons, the author sought to obtain 

 methods which were more trustworthy. The following method is recommended : 



"A small lead cup about 1 cm. in diameter and depth was made by running 

 the melted metal into a mold, and a flat piece of lead with a small hole in the 

 center was used as a cover. Into this cup a small amount of finely powdered 

 calcium fluorid, generally about 0.1 gm., was placed together with the silicate, 

 and the mixture covered with a few drops of concentrated sulphuric acid, added 

 by means of a medicine dropper or fountain pen filler. Upon the upper side 

 of the cover a piece of moistened black filter paper was placed and upon this 

 a small moistened pad of ordinary filter paper was laid to keep the black paper 

 moist during a heating of about 10 minutes upon a steam bath. At the con- 

 clusion of the heating a white deposit was found on the underside of the black 

 paper over the opening in the cover, if silica was present in appi-eciable amount." 



The converse of the above method can be employed for the detection of fluo- 

 rids, but here it is not quite so delicate, although good results can be obtained 

 if 1 mg. of fluorin is present. 



The valuation of chemical fertilizers of the superphosphate industry, 

 (Ztschr. Offentl. Chem., 17 (1911), No. 14, pp. 262-265).— This includes the 

 rules for sampling and the permissible limits of accuracy in analyses as to what 

 constitutes a just demand for determining low-grade fertilizers, etc., as com- 

 piled by the Association of Commercial Analytical Chemists and the Fertilizer 

 Manufacturers' Association of Germany. 



