AGEICULTUEAL CHEMISTRY AGROTECHNY. 11$ 



pi. 1). — Tlie Mattbaiopoulos method (E. S. R., 20, p. 705) has beeu modified 

 and simi)llfied iu so far that the results may be obtained more rapidly and are 

 more accurate. 



The metliod consists of diluting 17.5 cc. of milk with about 80 cc. of distilled 

 water in a 2()0 cc. flaslj. The milk is then neutralized with sodium hydrate 

 until a pink color is obtained with pheuolphthalein. (The authors find it ad- 

 vantageous to use a specially prepared color standard for this purpose.) The 

 casein is then precipitated at 65 to 75° F. with a standard acetic acid solution 

 (79.5 cc. normal solution diluted to 1,000 cc), adding this in 5 cc. amounts, 

 and agitating after each addition. When 25 cc. have been added the casein is 

 examined as to its flocculence and as to whether the fluid above it is compara- 

 tively clear. If this is not so 1 cc. more of acid is added and the process is 

 continued until the desired result is obtained. The number of cubic centimeters 

 of acetic acid solution used is recorded as (A). The flask is then filled up to 

 the 200 cc. mark with distilled water, well shaken, and filtered through a dry 

 filter into a dry beaker. The filtrate must be clear. Then 100 cc. of filtrate is 

 pipetted off and titrated with a standard alkali solution (79.5 cc. normal 

 solution hydroxid diluted to 1 liter) until a pink tint constant toward phe- 

 uolphthalein is obtained. The number of cubic centimeters of alkali used is 



A 



recorded as (B). The calculation is ^^—B= Percentage of casein in the milk. 



A rapid method of determining the percentage of casein in milk, T. B. 

 Robertson {Jour. Itidufi. and Eiiyiii. Cliciii., 1 (I'JOU), No. 10, pp. 723-72.5). — 

 The metho<I consists of precipitating 50 cc. of diluted milk with 75 cc. of tenth- 

 normal acetic acid, filtering off the precipitate, and washing it with distilled 

 water. After the precipitate is allowed to drain for 1 hour, it is taken, together 

 with the filter paper, and macerated with decinormal sodium hydroxid solution 

 until all the casein is dissolved. The solution is then filtered and the refrac- 

 tive index of the filtrate determined with the Pulfrich refractometer. The 

 readings are taken within 1 minute of the angle of total reflection at 20° C. 



The calculation is made by taking the refractive index of decinormal sodium 

 hydroxid as 1.33444, when the number of grams of casein in 50 cc. milk equals 



jj^ \ 33444 



'- , vvhere n is the refractive index of the final solution as obtained 



0.00152 



above. 



The influence of cold on constants of fat, H. Wagner and P. Bohbisch 

 (Ztschr. Untersuch. Xahr. u. Gcnussmtl., 18 {1909), No. 6, pp. 366, 367).— 

 Samples of lard, oleomargarine, mutton tallow, and artificial food fat were 

 exposed to temperatures of — 7 to — 10° C. It was found that practically no 

 changes were apparent in the chemical constants save a change in the iodin 

 number. The melting and solidifying points changed slightly. 



The influence of preservatives on the Reichert-Meissl number, C. Grimaldi 

 (Chcm. Ztfj., 32 (1908), Xo. 67, p. 7.9.}; ahs. in Ztschr. Untersuch. Nahr. ti. 

 Genussmtl., 18 {1909), No. 6, pp. 381, 382). — The presence of benzoic acid in 

 butter, oleomargarine, and coco fat increases the Reichert-Meissl number 

 slightly, the increase being proportional to the amount present. Salicylic acid 

 increases the Reichert-Meissl number in oleomargarine and coco fat, but less 

 so than benzoic acid, and decreases it in cow butter if the amount present is 

 over 0.5 per cent. 



The refraction of butter fat, margarin, lard, cocoa butter, and coco fat, 

 H. Matthes and F. Streitberger {Pharm. Zentralhalle, Jf9 {1908), No. 7, pp. 

 119-121; (iTjs. in Ztschr. Untersuch. Nahr. u. Genussmtl., 18 {1909), No. 6, 

 p. 380). — The differences between the refraction of the fat and the nonvolatile 

 fatty acids are for butter 11.2 to 11.5, margarin 13.2 to 13.7, coco fat 16.1 to 



