302 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



upon a small wet filter, wash the fat off the surface with 

 tap water and dry the filter. If the filter paper is colored 

 orange the presence of annatto is indicated. The appli- 

 cation of stannous chloride will change the color to a 

 characteristic pink if annatto is present. 



If the curd is colorless after it has been extracted 

 with ether no other coloring matter is present. If it 

 is orange or brownish the presence of analin orange or 

 caramel is indicated. The curd is then shaken in a test 

 tube with concentrated hydrochloric acid. If the solu- 

 tion immediately turns pink the presence of analin orange 

 is indicated. If it slowly turns blue, this points to the 

 presence of caramel and the following test should be 

 applied: About 120 c.c. of the milk and an equal quan- 

 tity of alcohol are mixed together and filtered. A small 

 quantity of subacetate of lead is added to the filtrate and 

 the precipitate produced is collected on a small paper 

 filter which is dried in an atmosphere free from hydrogen 

 sulphide. If caramel is present the precipitate is of a 

 dark brown color. If no caramel is present the pre- 

 cipitate will be white or straw color. 



