u6 MILK AND DAIRY PRODUCTS PART 



precipitate is about 2 c.c. ; where 50 per cent, is present, the 

 test-tube is almost completely filled with the precipitate. An 

 addition of less than 20 per cent, of goat's milk cannot be proved 

 with certainty by this method. Steinegger has modified his 

 method latterly, and now separates the milk in a small 

 separator, so that it contains less than 0'3 per cent, of fat. The 

 addition of ammonia now gives a precipitate which sinks to the 

 bottom of the tube, and it is much easier to distinguish it and to 

 estimate the amount. 



The method cannot be used for milk more than 24 hours old, 

 nor for colostrum, or milk mixed with colostrum. It cannot be 

 used either for the milk of sick and diseased animals, nor, in 

 fact, for abnormal milk of whatever origin. 



V. THE DETECTION OF ARTIFICIAL COLOURING. 



The Institute for Hygiene in Hamburg has worked out the 

 following method for the detection of artificial colouring matter 

 in milk or cream : One hundred to two hundred c.c. of milk or 

 cream are made faintly acid with acetic acid, or are allowed to 

 sour spontaneously, and then warmed to 80 C. The curd, which 

 contains fat and the colouring substance in addition to the 

 protein matter, is separated from the serum by filtration through 

 a cloth, digested twice with water to get rid of milk sugar, and 

 then well pressed. The moist curd is then boiled repeatedly 

 with alcohol until no colour remains, and the different lots 

 of alcohol used for the extraction are evaporated down to 

 10 or 20 c.c. To the residue an equal quantity of absolute 

 alcohol is added, and the whole left in the ice-chest for twelve 

 hours. At the end of this time the solution will only contain 

 a little fat, and any colouring matter which is present will 

 be noticeable. A strip of filter paper is now dipped into the 

 liquid, which rises slowly by capillary attraction to the height 

 of the edge of the beaker and then evaporates. 



When the milk is pure a faint yellow or brown band of 

 colour forms on the upper part of the paper., whereas any added 

 colouring matter causes a more pronounced shade, varying from 

 pink to deep orange, to form below the band given by pure 

 milk. The strip of paper is freed from fat by washing with 



