AGRICULTURAL CHEMISTRY AGROTECHNY. 607 



Experimental data indicate that very accurate results can be obtained with 

 the method. 



Experimental data com.paring the delicacy of diflEerent tests for hydrogen 

 peroxid in milk, I. T. Darlington (Jour. Indus, and Engin. Chem., 7 (1915), 

 No. 8, p. 676). — Of the various reagents in general use for the detection of 

 hydrogen peroxid, p-phenylenediamin and benzidin were found to give the 

 most delicate tests for its presence in raw milk. Quantities as low as 0.75 mg. 

 in 100 cc. of milk could be detected by these reagents. In the amounts ordi- 

 narily added to milk as a preservative, it could not be detected after 18 hours 

 standing. 



The apparent effect of acetic acid upon the constants of butter fat, C. 

 Bahljian (Jour. Indus, and Engin. Chem., 7 {1915), No. S, pp. 680, 681). — When 

 fats are separated from dairy products in the presence of strong acetic acid, 

 some of the acid is retained mechanically by the fat and affects the re- 

 fractometer reading, saponification value, and Reichert-Meissl value. Correct 

 values for these constants may be obtained with the acetic-sulphuric-acid 

 method by heating the fat at from 90 to 95° 0. for one hour before making 

 the determination. Hydrochloric and sulphuric acids, when used for the sep- 

 aration of the fat, are not retained to any appreciable extent and give correct 

 results. 



Chemical technology and analysis of oils, fats, and waxes, J. Lewkowitsch 

 (London: Macmlllan cC- Co., Ltd., 5. ed., rev. and enl., 191S, vol. 1, pp. XXIV -\- 

 668, figs. 59; 19U, vol. 2, pp. XIV+9U, flffs. 19; 1915, vol. 3, pp. VIII+483, figs. 

 27). — ^An entirely rewritten and revised edition of that previously noted (E. S. 

 R., 21, p. 518). New analytical methods have been incorporated and an endeavor 

 made to eliminate what has become antiquated. 



The quantitative deteiToination of creatin in muscle and other organs, 

 N. W. Janney and N. R. Blatherwick (Jour. Biol. Chem., 21 (1915), No. 3, 

 pp. 567-582). — This includes a study of the origin of creatin and creatinin, 

 combined with an investigation of previously described procedures for the 

 quantitative determination of creatin in muscle and organs. The authors 

 conclude that " creatin and creatinin are probably not to be regarded as exist- 

 ing in firm combination in liver and muscle, as acid hydx'olysis of such organs, 

 previously freed of these substances by extraction, fails to yield additional 

 creatin or its anhydrid." 



Criticisms on previously described methods are offered and improved pro- 

 cedures for the determination of creatin in muscle and other organs described. 



A method for the determination of chlorids in small amounts of body 

 fluids, F. C. McLean and D. D. Van Slyke (Jour. Biol. Chem., 21 (1915), No. 

 2, pp. 361-370). — The method was devised for using quantities of material as 

 small as 0.5 cc. and to obtain an accuracy of 1 part per 100. The determination 

 requires two steps: (1) Removal of proteins and (2) titration of chlorids. 



The proteins may be removed by coagulation or by ignition, the results being 

 identical by both methods. Coagulation is, however, simpler in routine work. 

 After removal of the proteins " the chlorids are precipitated in the presence of 

 nitric acid by standard silver nitrate solution, the silver chlorid is removed 

 by filtration, and the excess silver titrated with standard potassium iodid. 

 The titration is performed in the presence of nitrous acid and starch, so that 

 the first drop of iodid in excess of the silver present is changed to free iodin 

 and gives the blue starch- iodin color. The optimum acidity for the end point 

 is fixed by the addition of trisodium citrate in amount equivalent (one-third 

 molar) to the free nitric acid present. Under these conditions one drop of 

 excess fiftieth- normal iodid gives a color perceptible in 150 cc. of solution." 



