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. 
