804 EXPERIMENT STATION RECORD. 



method was made. The results obtained are essentially in agreement with those 

 of Heubner, noted above. 



" Gregersen's modification [K. S. R., 20, p. Ill] to overtitrate the dissolved 

 yellow precipitate with 0.5 normal H2SO4, with a view to remove the carbon 

 dioxid present by boiling, and then titrate back with 0.5 normal NaOH, while in 

 principle correct, is inconvenient, since it increased the time required for each 

 individual analysis. Instead of Gregersen's modification, it is best to run a 

 blank analysis — or, better, several blank analyses — ^which compensates the 

 errors due (a) to impurities (phosphorus) present in the reagents employed, 

 (b) to carbon dioxid contained in the liquids to be titrated, and (c) to the 

 acidity caused by the action of the boiling standard alkali on the filter paper. 

 The figure secured for the blank analysis is to be subtracted from the acidi- 

 metric analysis proper. With uniform work the same blank may be applied 

 to one or even several series of phosphoric-acid estimations." 



An extremely delicate colorimetric method for detecting and estimating 

 nitrates and nitrites, E. A. Letts and Florence W. Kea (Jour. Chem. Hoc. 

 [London], 105 (1914), No. 618, pp. 1151-1161). — For detecting nitrates and 

 nitrites 0.5 cc. of the solution under examination is mixed with 1.3 cc. of 

 sulphuric acid in a small porcelain crucible, and, after mixing with a glass rod, 

 0.5 cc. of diphenylbenzidin (0.01 gm. in 50 cc. of sulphuric acid) is added. A 

 blue color indicates either form of oxidized nitrogen. Details for the quantita- 

 tive determination are given. In the method the depth of color produced is 

 compared with that resulting in a nitrate solution of known strength. When 

 nitrites are in admixture with nitrates it becomes necessary to oxidize the 

 nitrous acid to nitric acid with potassium permanganate. 



Fat analysis in fat chemistry in 1913, W. Fahrion (Ztschr. Angew. Chem., 

 27 (1014), No. 40, Aufsatsteil, pp. 273-290). — An extensive review of the 

 literature on this subject. 



Determination of formic and acetic acids, E. Heuser (Chem. Ztg., 39 (1915), 

 No. 10-11, pp. 57-59, fig. 1). — The usual method of determining formic and acetic 

 acids by acidifying with sulphuric acid and distilling with steam requires too 

 much time for its execution. Furthermore if phosphoric acid is substituted 

 for sulphuric acids the results are influenced, since the former passes over into 

 the distillate. If, however, the vapors are passed through a llask filled with 

 glass beads and heated on a water bath satisfactory results can be obtained. 



The method proposed consists of mixing the sample with 50 cc. of water 

 and 50 cc. of phosphoric acid (specific gravity 1.2) and distilling at 44° C. and 

 56 mm. pressure until a volume of 500 cc. remains in the distillation flask. 

 Then 50 cc. more of water is added to the flask, and distillation is conducted as 

 before. Carbon dioxid is passed through the flask during the distillation. A 

 flask with glass beads is also necessary when acetic acid is being determined 

 in a solution containing both acetic and formic acids. Formic acid is oxidized 

 with potassium dichromate. 



The estimation of boric acid in substances, alimentary or otherwise, Jay 

 (Compt. Rend. Acad. Sci. IParis'], 158 (1914), No. 5, pp. 357, 358; abs. in Jour. 

 Chem. Soc. [London], 106 (1914), No. 617, II, p. 217).— A claim for priority 

 over the Bertrand and Agulhon methods. See also work previously noted 

 (E. S. R., 32, p. 206). 



Method for the exarhination of meat extracts, J. Smorodinzew (Hoppe- 

 Seylcr's Ztschr. Physiol. Chem., 92 (1914), No. 2, pp. 214-220; obs. in Ztschr. 

 Angew. Chem., 27 (1914), No. 91, Refer at enteil, p. 629).— The highest yield of 

 purins and carnosin was obtained by precipitating with mercuric sulphate. 

 Precipitating with phosphotungstic acid with an addition of sulphuric acid 



