1917] AGRICULTXTEAL CHEMISTRY AGEOTECHNY. 507 



quantity of extraneous material should be controlled by a simple method of 

 examination. 



The determination of gum in gum sirups, E. Luce {Ann. Falsif., 9 il916). 

 No. 92-9S, pp. 227-231). — The author briefly describes and comments on the 

 methods of Roussin, Bellier (E. S. R., 25, p. 109), and Rocques and Sellier 

 (E. S. R., 28, p. 206). Analytical results obtained show that either the pro- 

 cedure of Rocques and Sellier or that of Bellier is of practical value, the former 

 being slightly the more accurate. The presence of dextrin causes high results. 

 This, however, is a valuable indication of adulteration and a cause for the 

 rejection of the material as nonofRcial. 



The polariscopic examination of gum sirups before and after inversion is 

 deemed to be an excellent and accurate procedure. 



A new method for the determination of vanillin in vanilla extract, A. W. 

 Dox and G. P. Plaisance {Amer. Jour. Pharm., 88 0916), Xo. 11, pp. 481-/,84).— 

 The authors at the Iowa Experiment Station describe the following gravimetric 

 procedure based on the reaction of thiobarbituric acid and certain aromatic 

 aldehydes previously noted (E. S. R., 36, p. 318) for the determination of 

 vanillin : 



Twenty-five cc. of the extract is dealcoholized in the usual manner, trans- 

 ferred to a 50-cc. standard sugar flask, and filled to the mark with lead acetate 

 solution. After standing for several hours at about 37° C. the contents of the 

 flask are filtered through a dry filter, 40 cc. of this filtrate is transferred to 

 another 50-cc. flask, and suflicient hydrochloric acid added to bring the volume 

 to 50 cc. and the acidity to 12 per cent. After standing for a few minutes the 

 lead chlorid is filtered off and 40 cc. of the filtrate taken for the determination. 

 Thiobarbituric acid in 12 per cent hydrochloric-acid solution is added, and an 

 orange-colored precipitate results. The precipitate is allowed to stand over- 

 night, filtered on a Gooch crucible, washed with hydrochloric acid, and dried 

 at 98". A simple correction for slight solubility is necessary. Analytical data 

 submitted indicate the accuracy of the procedure. 



The method is not applicable, however, to extracts which contain caramel, 

 since the caramel contains furfural derivatives which react with thiobarbituric 

 acid. When caramel is present the filtrate after clarification is brown instead 

 of straw colored. A very delicate test was devised by the authors in which 

 after clarifying and removing the excess of lead as chlorid, phloroglucinol is 

 added. In the presence of caramel a brown precipitate is formed, and in its 

 absence the vanillin gives a delicate rose pink color or slight pink precipitate. 



The use of amyl alcohol in Gerber's method for the determination of fat 

 in milk, Orla-Jensen (Mcelkeritid., 29 (1916), No. 7, pp. 104-106).— From a 

 comparison of the Babcock and Gerber methods it is indicated that the latter 

 in general yields the higher results, the error increasing with the percentage of 

 fat in the milk. The necessity of using amyl alcohol of standard purity is 

 enipliasized. 



The biological method for judging the freshness of milk according to 

 Parashchuk (Paraschtschuk), P. Kalantaeov (Vtestnik Bald. Agron. Sta. V. K. 

 Ferrein, No. 21 (1914). pp- 84-98). — The author investigated the method pre- 

 viously noted (E. S. R., 31, p. 508), and found that all the strains of lactic 

 acid bacteria will grow well in the three grades of milk, very fresh, fresh, 

 and old. No evidence of any difference in action in the sense indicated by the 

 originator of the method was noted. 



Other experiments were carried on with various combinations of the micro- 

 organisms recommended in the original procedure, with the same negative 

 results. 



It is concluded that the method is absolutely impracticable and unreliable. 



