122 METHODS OF ANALYSIS. 



curd free from adhering liquid, transfer to a small flask, and macerate for 

 several hours (preferably overnight) in about 50 cc of ether, the flask being 

 tightly corked and shaken at intervals. 



(1) DETECTION OF ANNATTO (IN THE ETHER EXTBACT). 



Decant the ether extract as obtained above into an evaporating dish, place 

 on the water bath, and evaporate the ether. Make the fatty residue alkaline 

 with sodium hydroxid, and pour upon a very small wet filter while still warm. 

 After the solution has passed through, wash the fat from the filter with a 

 stream of w r ater and dry the paper. If, after drying, the paper is colored 

 orange, the presence of annatto is indicated. Confirm by applying a drop of 

 stannous chlorid solution, which, in presence of annatto, produces a character- 

 istic pink on the orange-colored paper. 



(2) DETECTION OF ANIL1N ORANGE (IN THE CURD). 



The curd of an uncolored milk is perfectly white after complete extraction 

 with ether, as is also that of a milk colored with annatto. 



If the extracted fat-free curd is distinctly dyed an orange or yellowish color, 

 anilin orange is indicated. To confirm the presence of this color, treat a lump 

 of the fat-free curd in a test tube with a little strong hydrochloric acid. If the 

 curd immediately turns pink, the presence of anilin orange is assured. 



(3) DETECTION OF CARAMEL (IN THE CURD). 



If the fat-free curd is colored a dull brown, caramel is to be suspect* 

 Shake a lump of the curd, as in (2), with strong hydrochloric acid in a tt 

 tube and heat gently. In the presence of caramel the acid solution will gradi 

 ally turn a deep blue, as will also the white, fat-free curd of an uncolored 

 milk, while the curd itself does not change color. It is only when this blue 

 coloration of the acid occurs in connection with a brown colored curd, which 

 itself does not change color, that caramel is to be suspected, as distinguished 

 from the pink coloration produced at once under similar conditions by anilin 

 orange. 



(b) LYTHGOE'S TEST FOB ANILIN ORANGE. PROVISIONAL. 



Treat about 10 cc of the milk with an equal volume of hydrochloric ac-id 

 (sp. gr. 1.20) in a porcelain casserole and give the dish a slight rotary motion. 

 If an appreciable amount of anilin orange is present, a pink color will at once 

 be imparted to the curd particles as they separate. 



CREAM. 



Most of tho methods for milk analysis may bo applied to cream, properly 

 diluted. For accurate work the dilution should in most rases l>> made after 

 the cream has been weighed (not measured) for the determination, si nco cream | 

 tends to separate quickly from water. In the Habcock centrifugal method 

 cream should always bo weighed into the test bottle before diluting. 



CONDENSED MILK. PROVISIONAL. 



1. Preparation of Sample. 



Mix thoroughly by transferring the contents of the can to a large evaporating 

 dish and stirring it with a pestle until homogeneous. Weigh 40 grams of tbe 

 mixed sample in a 100 cc flask, or transfer thereto by washing, and make up I 

 to the mark with water. 



