612 EXPEEIMENT STATION EECOED. 



of substances containing magnesium sulphate will, when ignited, consist of 

 magnesium osid. The quantity of magnesium sulphate in a substance^ con- 

 taining chlorids may be sufficient to cause the total loss of the chlorin on incin- 

 eration. 



Volumetric determination of copper, G. Zuccari (Ann. Chim. Appl. IRome], 

 2 (1914), Nos. 9-10, pp. 287-290) .—The solution of the salt is titrated with a 

 solution of a sodium nitroprussid which contains 46.S66 gm. per liter until a 

 filter paper moistened with ammonium sulphid becomes colored. One cc. of 

 the sodium nitroprussid solution=0.01 gm. of copper. Free acids or salts of 

 ferric iron, zinc (save in high concentration), tin, aluminum, lead, manganese, 

 and certain other metals do not affect the results, and the method can be applied 

 directly to solutions of copper which do not contain nickel or cadmium. 



Detection of vegetable fats in animal fats, M. Klostermann (Ztschr, 

 Vntersuch. Nahr. n. Genussmtl., 26 (1913), No. 9, pp. 433-437; abs. in Jour. 

 Soc. Chem. Indus., 32 (1913), No. 23, p. 1118).— The Marcusson and Schilling 

 method was not found always applicable, since digitonin precipitates only free 

 cholesterol and phytosterol and not their esters. 



" Saponification is essential, and the following method is recommended : One 

 hundred gm. of the fat is saponified with alcoholic potassium hydrosid, the soap 

 solution diluted with water, and the fatty acids liberated by hydrochloric acid 

 and extracted with 250 cc. of ether. The ethereal solution is washed with 

 water and shaken with 250 cc. of petroleum spirit and about 25 gm. of sodium 

 chlorid, which is subsequently separated by filtration through cotton wool. The 

 filtrate is heated and treated with a solution of 1 gm. of digitonin in 20 cc. of 

 90 per cent alcohol, and the crystalline precipitate separated after 15 minutes 

 and washed with ether until free from fat. It is then dried with filter paper 

 and acetylated with 20 to 30 cc. of acetic anhydrid. The excess of acetic 

 anhydrid is evaporated, the residue dissolved in 50 cc. of absolute alcohol, and 

 the solution treated drop by drop with water until crystals begin to separate. 

 More water, up to 25 cc. in all, is then added and the crystals filtered on cotton 

 wool, washed with 70 per cent alcohol, and dissolved in ether. The solution 

 is evaporated to dryness and the acetates are recrystallized from absolute 

 alcohol and examined in the usual way." 



The separation of sterins from fats with digitonin, P. Berg and J. Angee- 

 HAUSEN (Chem. Ztg., 38 (1914), No. 93, pp. 978, 979; abs. in Ztschr. Angew. 

 Chem., 27 (1914), No. 91, Referatenteil, p. 6^^).— The value of the Windaus 

 method for separating sterins with digitonin was studied. It was deemed 

 especially desirable to know whether the method could be employed for food- 

 control work, and, furthermore, whether the procedure could furnish new ways 

 for investigating the unsaponifiable constituents of fats. 



A modification of the IMarcusson and Schilling, Klostermann, and Fritzsche 

 methods (which utilize the Windaus principle) was finally decided upon. The 

 solvent employed was chloroform saturated with digitonin at 60 to 70° C. 

 Twice as much acetic acid anhydrid was employed for acetylation as is recom- 

 mended by Marcusson and Schilling. For quantitative purposes the Kloster- 

 mann procedure for separating the acetates is recommended. The sterin-free 

 portion of animal fats does not seem to possess optical activity, but in plant 

 fats and hardened animal fats optical activity of the sterin-free part is often 

 observed. In hardened fats the optical activities are dextrorotary. It is 

 thought that this optical property might eventually be employed for detecting 

 hydrogenated fats. 



Methods for the quantitative estimation of mannit, J. Smit (Ztschr. 

 Analyt. Chem., 53 (1914), No. 8, pp. 473-490; abs. in Ztschr. Angetc. Chem., 27 



