AGRICULTURAL CHEMISTRY AGROTECTINY. 707 



dilutinir the milk 1 : KKt and 1 : "lOO, accordinji to the supposed pollution, niixiug 

 the milk and media on the phite. and, after solidification, placing; the plate in 

 the incuhator at 37° C. and making; the hacterial count at the expiration of 24 

 hours. 



Some mineral substances wliich give the peroxydase reaction, J. Wolif 

 (Compt. Rend. Acad. Sci. [Paris], lJi6 (1008), No. 3, pp. J.'i2-lJiJ,; abs. in Zentbl. 

 Agr. Chcin., 38 (1009), Xo. .'/, /)/). 278, 270). — Iron oxysulphate, even in dilutions 

 of 1 : 6,000,000, gives a coloration with gualac tincture which has stood for a 

 while. At concentrations of 100 mg. per liter this coloration is very intense. 

 Fres'hly prepared gualac tincture does not give the reaction, hut if liydrogen 

 peroxid is added the reaction heeomes very marked; if the diluted iron solution 

 is boiled with hydrogen peroxid, however, the reaction does not talvo place. 

 Small amounts of mineral acid retard the reaction. 



The retarding- of the rennin action by milk, K. Sciiern (Biocheni. Ztschr.. 

 20 (1000), yo. 3-5, pp. 23 l-2.'il).— It is shown by the results of fhis investiga- 

 tion that it is possible to detect milk of pathogenic animals, that is. animals 

 suffering from mastitis, etc., by testing the retarding action of such milk upon 

 rennet. 



The detection and estimation of formaldehyde in milk, J. C. Brunnich (Rpl. 

 Austral. Assoc. Adv. Sci., 11 (1001). pp. SJ/S, 3.'i0). — A critical study of various 

 methods employed for the detection and determination of formaldehyde in milk. 



"(1) For the qualitative detection of formaldehyde in fresh milk, Eury's or 

 Bonnet's morphin test may be applied to the samples direct, and tests with 

 Sehiff's reagent, resorcin. phloroglucin, gallic acid, and phenylhydrazin to the 

 distillate. (2) The qualitative detection of formaldehyde in old and sour 

 milks presents no ditiiculties. (.3) For the estimation of minute traces of 

 formaldehyde in fresh milk, colorimetric methods— either Bonnet's, with the 

 original samples, or 8chifE's reagent, with the distillate — may be used with 

 advantage. (4) In milks kept any length of time these methods will indicate 

 a less quantity of formaldehyde than was originally present, depending mainly 

 on the length of keeping." 



Detection of small quantities of benzoic acid, salicylic acid, and saccharin 

 in cream, G. W. Monier-Williams (Local Govt. Bd. [Gt. Brit.], Food Rpts.. 

 1000, Xo. 10, p. 33). — By this method 100 cc. of cream are acidified with 1 cc. 

 concentrated phosphoric acid and heated with constant stirring in a porcelain 

 dish on an asbestos gauze until all the water has been driven off, care being 

 taken not to heat over 120° C. The clear fat is then filtered through a dry 

 filter, allowed to cool to 60 or 70°, and shaken out with 50 cc. of a 5 per cent 

 solution of sodium bicarbonate, which has been previously heated to the tem- 

 lierature of the fat. The turbid alkaline extract is then filtered through a wet 

 filter, made acid with 1 cc. of hydrochloric acid, cooled, and extracted 3 times 

 with ether. The i-emainder of the procedure is that usually followed. 



The action of light on butter fat, M. Siegfeld (ililchu: Zentbl., .'/ (1008), Xo. 

 12, pp. 530-532; abs. in Molk. Ztg. [Hildesheim], 23 (1900), No. 31, p. 10.',5).— 

 Melted and filtered butter fat is very stable when stored in the dark, but when 

 exposed to the light it takes on a disagreeable odor and becomes bleached. 

 Among the changes which take place are a gain in weight and acidity, an 

 increase in the Reichert-Meissl. saponification, and Polenske numbers, and a 

 diminution in the iodin number. The volatile fatty acids of medium molecular 

 weight do not change perceptibly, but the amount of solid nonvolatile acid 

 becomes much higher. Oxidation is at once apparent. 



Does the presence of iron in butter indicate poor quality? 11. IIuft (Milchw. 

 Zentbl, 5 (1900), No. (1. pp. 250-252; abs. in Chem. Zentbl., 1000, II, Xo. 2, 

 15149— No. S— 09 2 



