Colouring Matter for Dairy Produce. 391 



The apparatus is based on the prrysiological property that 

 the air-bubble at the blunt end of the egg increases in size 

 with the growth of the embryo. "When the egg is placed in 

 liquid it has consequently an increasing tendency to become 

 vertical, with the blunt end uppermost. The apparatus itself 

 consists of a glass vessel, bearing at the back lines drawn at 

 various angles, each line being marked with the age. The 

 vessel is filled with some harmless liquid, in which the eggs 

 to be tested are laid. Each egg will take up a certain posi- 

 tion, and. according to its age, its longer axis will be more 

 or less inclined to the horizon. The direction of this axis is 

 compared with the lines at the back of the vessel, and the age 

 of the egg read off at the line to which its axis is parallel. 



A new-laid egg lies horizontally at the bottom of the 

 vessel. An egg three to five days old raises itself from the 

 horizontal so that its axis makes an angle of about 20 deg. 

 At eight days old this angle has increased to about 45 deg. 

 at fourteen days it is 60 deg., at about three weeks it is 

 75 deg., and after four weeks it stands upright on the pointed 

 end. A bad egg, or one more than five wee&s old, floats. 

 With practice it is stated that the age can be told to a day. 



The most commonly used colouring matter for dairy 



produce is annatto, a vegetable extract 



Colouring- Matter f r0 m Bixa ordlana. This, and certai 1 

 for 



Dairy Produce. other y ellow colouring matters of vege- 

 table origin 'turmeric, saffron, etc.), have 

 generally been considered harmless in the quantities 

 employed, but they are gradually being superseded by coal- 

 tar yellows, the action of which upon the human system is 

 not fully known. Butter from Holland, Australia, and the 

 United States is very frequently coloured with coal-tar 

 yellows. A large number of margarines are also so coloured. 

 The coal-tar yellow most frequently employed for dairy 

 produce and margarine is known commercially as " butter 

 yellow," its chemical title being " Dimethyl-amido-azo- 



