106 



MANUAL OF MILK PRODUCTS 



:=-10 



drop at a time just to the mark. Any drops of liquid adhering 

 to the inside walls of the neck must be removed, using con- 



Oveniently a strip of blotting or filter paper. 

 The tester is then slowly lowered into the neck 

 of the test bottle until the liquid rises halfway 

 between the two sections of the instrument, 

 when the upper surface of the liquid should be 

 at the 5 per cent mark, if the scale is correct 

 to this point. If the surface of the liquid is 

 above or below the 5 per cent mark, then the 

 scale is incorrect to that extent. After the 

 accuracy of the 5 per cent mark is tested, 

 the instrument is then lowered into the bottle 

 until the liquid rises about one-eighth of an 

 inch above the top of the upper section of the 

 tester. If the upper surface of the liquid is 

 level with the 10 per cent mark, the graduation 

 is correct at that point. The graduation of 

 the scale is regarded as correct, if the tester 

 shows the 5 and 10 per cent marks to be 

 correct. 



"In explanation of the use of this form of 

 bottle-tester, it is to be remembered that the 

 neck of the milk bottle is so graduated as to 

 hold 2 c.c. between the and 10 marks ; hence, 

 the volume between the and 5 marks should 

 be 1 c.c. and that between the 5 and 10 marks 

 should be also 1 c.c. The brass plunger is so 

 made that each section displaces, or forces up 

 into the neck, 1 c.c. of liquid, the whole instru- 

 ment displacing 2 c.c. This tester therefore gives two tests 

 of the scale, one at the 5 per cent mark and the other at the 

 10 mark. 



" Some of these instruments are made to test the 4 and 8 per 



Fig. 5. — De- 

 vice for testing 

 accuracy of milk- 

 bottle. 



