AGRICULTURAL CHEMISTRY — AGROTECHNY. H 



Determination of starch in cereals by means of the Zeiss immersion 

 refractometer, L. M. Lai.in (Ztschr. Gcsam. Brauw., 32 (1909), pp. 231-233- 



abs. ill Jour. Soc. Chem. Indus., 28 {1909), No. 11, pp. 617, 618). The Zeiss 



immersion refractometer was employed to determine the refraction during the 

 various stages of the hydrolysis of starch. It was apparent that the coefficient 

 of refraction did not change with the enzymic action until a point was arrived 

 at in which iodin produced no reaction. Different starches were tested in this 

 relation, as well as Lintner's soluble starch. The diastase employed in these 

 tests was obtained by precipitating cold infusions obtained from a well-grown 

 malt rich in protein with ammonium sulphate. The concentration of the starch 

 solution varied between 1 and 5 per cent, and each gram of starch employed Wiis 

 found to be equivalent to 4 degrees on the scale of the refractometer. 



The method is as follows : Two or 3 gm. of material finely ground are tritu- 

 rated heavily in a mortar with a little water and transferred to a 100 cc. flask, 

 which is then filled up to about SO cc. To this is added 0.2 cc. of a 1 per cent 

 solution of the diastase, and the mixture heated for 5 minutes in the boiling 

 water bath and finally cooled to room temperature. A further addition of 

 0.2 or 0.3 cc. of diastase solution is made, the flask kept at 55 to 60° C. for 4 

 hour, then cooled and made up to the 1(X) cc. mark at 17.5°. A correction is 

 then made for the refraction of the soluble constituents of the cereal. This is 

 obtained by pulverizing 2 or 3 gm. in the mortar with small amounts of water, 

 introducing the mass into a 100 cc. flask, filling to the 100 cc. graduation with 

 watei', filtering after agitating well, and establishing the refraction at 17.5°, 

 The results obtained with the method compare closely with the figures obtained 

 by the Lintner polarimetric method. 



Detection of cruciferous oils in oil mixtures, D. Hoi.de and J. Marcusson 

 (Ztschr. Angeiv. Chem., 23 (1910), No. 21, pp. 1260-1262) .—The chief repre- 

 sentative of the oils of this order is rape oil. The reaction utilized by the 

 autliors is based on the precipitation of erucic acid and determining its molecu- 

 lar weight, as follows : 



From 20 to 25 gm. of the oil to be examined is dissolved in a double volume 

 of 96 per cent alcohol in a wide-mouth test tube, and cooled to —20° C. with 

 the aid of an ice-aud-salt mixture, stirring the oil during the cooling process. 

 The precipitate of fatty acids is collected on a cold funnel (such as is employed 

 in determining the paraffin content of oils according to the alcohol-ether 

 method), rendered dry with the suction pump, and washed with cold alcohol 

 two or three times. The filtrate is concentrated, and the residue taken up with 

 four times its volume of alcohol (75 volume per cent) and cooled to —20°. 

 If cruciferous oils are present, a precipitate forms upon stirring and after about 

 1 hour, which, upon washing with 75 per cent alcohol, appears white and con- 

 sists mostly of erucic acid. This is dissolved in benzol or ether on the filter, 

 the filtrate concentrated, and the molecular weight of the residue determined 

 by the titration method. The molecular weight, if rape oil or other cruciferous 

 oil is the substance employed, lies between 310 and 320, while that of pure 

 erucic acid is 338. 



The detection of rape oil in olive oil and other edible oils, M. Tortelli 

 and V. FoRTiNi (Cliem. Ztg., 3J, (1910), No. 78, pp. 689, 690).— The method is 

 based on the detection in the suspected sample of the erucic acid contained in 

 rape oil by three successive determinations, as follows: (1) The iodin number 

 of the fatty acids, which yield insoluble or only slightly soluble lead soaps; 

 (2) the melting point of the lead soaps; and (3) the critical solution tempera- 

 ture of the sodium salt which is obtained by the decomposition of the lead 

 soaps. See also the abstract noted above. 



