316 EXPERIMENT STATION RECORD. [Vol. 36 



in the speed of sugar formation, together with the high ratio of amyloclastic 

 to saccharogenic power, indicate that this amylase is a more active catalyst of 

 the earlier than of the later stages of the hydrolysis." 



The data submitted indicate that " Lintner soluble starch is well adapted to 

 its purpose as substrate for testing the activities of the different amylases, 

 and that its use leads to conservative estimates of the diastatlc powers of 

 purified preparations." 



An examination of certain methods for the study of proteolytic action, 

 H. C. Sherman and Doea E. Neun (Jour. Amer. Chem. Soc, 38 {1916), No. 10, 

 pp. 2199-2216, figs. 4). — The Mett method for determination of total nitrogen 

 of digestion products, the measurement of the increase of amino nitrogen by 

 the Van Slyke method, the titration of the acidity of digestion products, the 

 increase of electrical conductivity, the polariscopic method, and the biuret and 

 ninhydrin reactions for determining the proteolytic activity were studied in 

 detail. The experimental results are submitted in tabular form. 



It is indicated that in general the quantitative determination of the total 

 nitrogen or the amino nitrogen of the digestion products appears to be more 

 delicate as a means of detecting proteolysis than either the biuret or the nin- 

 hydrin reaction, and more delicate, accurate, and generally applicable than any 

 of the other quantitative methods studied. " The results emphasize the im- 

 portance, in quantitative comparisons, of so limiting the amount of enzyra 

 preparation and the time of its action as to keep within the region in which the 

 velocity of hydrolysis is directly proportional to the enzym concentration." 



Nitrog'en determinations by direct nesslerization, O. Folin and W. Denis 

 (Jour. Biol. Chem., 26 (1916), No. 2, pp. 473-506). — Five papers are presented. 



I. Total nitrogen in urine (pp. 473-489) . — A colorimetric procedure is described 

 in detail. For the digestion of the sample a mixture of phosphoric and sul- 

 phuric acids (3:1) is recommended on account of its markedly reducing the 

 amount of sulphate in the digested material and thus obviating the possible 

 precipitation of the colored mercury ammonium compound in the color com- 

 parison. 



Comparative analytical data with the standard Kjeldahl method indicate the 

 accuracy of the micro-procedure. 



Notes on the destructive digestion of urine, Nessler's reagent, the neutraliza- 

 tion and dilution of the digestion mixture, standard ammonium sulphate solu- 

 tions, the use of Ostwald pipettes, and the use of the colorimeter are included. 



II. Nonprotein ntirogen in blood (pp. 491-496). — Metaphosphoric acid (so- 

 called "glacial" phosphoric acid) has been found to be an excellent protein 

 precipitant. It is indicated as being better than colloidal iron and fully as 

 good as trichloroacetic acid. 



The determination of nonprotein nitrogen is described as follows : To 20 cc. 

 of water in a 50-cc. volumetric flask 5 cc. of blood is added, and then 3 cc. of a 

 25 per cent metaphosphoric acid. The liquid is thoroughly mixed and allowed 

 to stand for from 1 to 24 hours, after which the flask is filled to the mark, 

 thoroughly agitated, and the contents filtered through a dry filter. It is im- 

 portant that the mixture be allowed to stand for a sufficient time before filtration. 

 An aliquot, corresponding to 1 cc. of blood, of the perfectly clear and colorless 

 filtrate is used for determining the nitrogen, the procedure being essentially the 

 same as that used in urine samples. 



III. Ammonia in urine (pp. 497-499). — A procedure in which blood charcoal 

 (ammonia-free) is used to remove the creatinin and other reducing substances 

 found in urine, so that the nesslerized filtrates remain clear for several hours, 

 is described, A small amount of metaphosphoric acid is added to insure the 



