THE BABCOCK TEST 



49 



(2) Testing with special bottle-tester. The quick- 

 est method of testing the accuracy of the graduation 

 of a test-bottle is to use a special device, which is es- 

 sentially a simple brass plun- 

 ger (Fig. 19). This instru- 

 ment is divided into two equal 

 portions, each part being 

 made of such size as to dis- 

 place exactly one cubic centi- 

 meter of liquid. This bottle- 

 tester is used as follows: 

 The test-bottle is filled to the 

 zero mark with milk, or one 

 may use water or, better, 

 wood alcohol, imparting color 

 to the water or alcohol by 

 adding some black aniline or 

 carmine ink. Fill the bottle 

 nearly to the zero mark and 

 then finish with a pipette or 

 dropper, adding a drop at a 

 time just to the mark. Any 

 drops of liquid adhering to the 

 inside walls of the neck must 

 be removed, using conven- 

 iently a strip of blotting or 



FIG. IQ FIG. 20 



MILK-BOTTLE TESTING nlter paper. The tester is 

 TESTER ACCURACY OF then slowly lowered into the 



MILK-BOTTLE , - ^ ,1^1 .-i 



neck of the test-bottle until 



the liquid rises half way between the two sections of 

 the instrument, when the upper surface of the liquid 

 should be at the 5 per cent, mark (Fig. 20), if the scale 



