48 



MODERN METHODS OF TESTING MILK 



^^^ 



graduation a close-fitting cork or plug, cut off square 

 at the lower end. Turn the bottle upside down, caus- 

 ing the mercurv to run into the neck. The mercury 

 just fills the space in the neck between the o and lo 

 mark, if the graduation is accurate. The same 

 mercury can be used in the same way in test- 

 ing one bottle after another by 

 transferring all the mercury 

 from one bottle to another, which 

 may be conveniently done by 

 slipping a piece of elastic rub- 

 ber tubing over the ends of the 

 necks of the two bottles. In 

 using the same mercury for test- 

 ing one bottle after another, no 

 mercury must be lost in trans- 

 ferring, and none must be left 

 in the bottle last tested. The 

 inside walls of the test-bottle 

 must be dry and clean in order 

 to prevent any mercury adhering. 



(3) Testing zuith zcafcr. — The bottle to be tested 

 is filled with water, slightly colored with carmine ink, 

 or otherwise, up to the zero mark. The coloring of 

 the water makes easier the reading of the height of 

 the liquid. Any water adhering to the inside of the 

 neck is removed by a strip of blotting or filter paper. 

 Then one runs into the test-bottle 2 cc. of colored water 

 from a burette or pipette, graduated to twentieths of 

 a cubic centimeter. The upper surface of the liquid 

 should be on a level with the 10 per cent, mark if the 

 scale is correct. Any part of the scale can be similarly 



FIG. 21 

 BURETTE AND SUPPORT 



