1916] AGRICULTURAL CHEMISTRY AGROTECHNY. 615 



335). — The experimental data demonstrate that ammonium salts of weak acids 

 react positively with ninhydrin in concentrations of 1 per cent. In very high 

 concentrations the ammonium salts of strong mineral acids give a positive 

 ninhydrin reaction. Reducing agents increase the sensitiveness of the ninhy- 

 drin reaction with ammonium salts. 



" In the presence of pyridin and in a concentration of 1 cc. = 0.05 mg. of 

 nitrogen, all ammonium salts react positively with triketohydrindene hydrate. 

 The amount of decomposition of the ammonium nitrogen was found to be inde- 

 pendent of the acid radical attached and possessed a constant value of 0.018 

 mg. nitrogen ; the blue coloration is due to the ammonium salt of diketohydrin- 

 dylidene-diketohydrindamin." 



A theory as to the meelianism of the reaction with amino acids and am- 

 monium salts is sug.L,'ested. 



The ninhydrin reaction with am.ins and amids, V. J. Harding and R. M. 

 MacLean {Jour. Biol. Chem., 25 {1916), No. 2, pp. 337-350). — "The ninhydrin 

 reaction is given by organic bases of the type RCH2NH2, and R2CHNH2 where 

 one radical is negative in character. Other bases which readily yield ammonia 

 or are readily oxidized give the ninhydrin reaction. With the fatty amins and 

 in the presence of pyridin the strongest reaction is given by the simplest mem- 

 bers. Amids give no reaction with ninhydrin. Guanidin and its derivatives 

 give a negative test." 



The nonspecificity of the ninhydrin reaction for amino acids, especially in 

 vary small amounts and in the presence of large amounts of ammonium salts, 

 is emphasized. 



On the determination of phytosterol in animal fats according' to Bomer's 

 acetate procedure with the separation of the stearins by precipitation with 

 digitonin, B. KuHN, P. Bengen, and J. Wewekinke {Ztschr. Untersuch. Nahr. 

 u. Genussmtl, 29 {1915), No. 8, pp. 321-329) .—The authors outline a modified 

 procedure as follows : 



Fifty gm. of fat is heated with 100 cc. of alcoholic potassium hydroxid (200 

 gm. KOH dissolved in 70 per cent alcohol and made up to 1 liter) for 15 min- 

 utes on a water bath. The clear soap solution is diluted with 150 cc. hot water 

 and then 50 cc. hydrochloric acid (specific gravity 1.124) is addeil. The clear 

 fatty acids are then separated from the KCl-glycerin mixture by filtration. To 

 the warm liquid acids 25 cc. of a 1 per cent solution of digitonin in 96 per cent 

 alcohol is added, and the mixture is thoroughly stirred and allowed to set on 

 the water bath at a temperature of 70° C. for from 0.5 to 1 hour, according to 

 the amount of stearins present. To the mixture, from 15 to 30 cc. of chloro- 

 form is now added and the precipitate carefully filtered on a Witte plate with 

 gentle suction. The precipitate is washed from three to five times with chloro- 

 form and in the same manner with ether. When free from fatty acids it is 

 dried for ten minutes at from 90 to 100°. The precipitate is now strongly 

 boiled with from 3 to 5 cc. of acetic anhydrid for about five minutes, in which 

 time the reaction is usually complete. Four volumes of 50 per cent alcohol are 

 now added and the mixture cooled. After from five to ten minutes the pre- 

 cipitated acetate is filtered through a small filter, washed with 50 per cent 

 alcohol, and then recrystallized from ether solution. 



Analytical data of the melting points of stearin acetates obtained from 75 

 different samples of fats and mixtures are submitted. 



The determination of stearins by means of digitonin, O. Pfeifer {Ztschr. 

 Untersuch. Nahr. u. Genussmtl., 31 {1916), No. 2, pp. 38-^0). — The procedure 

 modified by Kiihn et al. (see previous abstract) was found to yield excellent 

 results. 



