LABORATORY EXERCISES 347 



it hang in a perpendicular position, on the level with the eye. Read 

 the mark or graduations at the extreme top and bottom of the fat 

 column. The difference between these is the percentage of fat in the 

 milk. Most test-bottles are made to read as high as 10 per cent. Each 

 percentage has its number marked on the glass and there are five 

 small spaces, each representing .2 per cent between these principal 

 marks. Thus, if the top of the fat column is even with the third short 

 mark above the 7 mark, the top reading would be 7.6; and if the bot- 

 tom is half way between the first and second short marks above the 

 3 mark, the bottom reading would be 3.3; the difference is 4.3, which 

 is the percentage of fat or number of pounds of fat in 100 pounds 

 of the milk tested. 



Xotes. One cc. means one cubic centimeter, or about twenty 

 drops. 



If the fat column is clouded with white specks, probably the acid 

 was not strong enough, or not enough was used, or the heat was not 

 high enough. ' 



If the fat column is clouded with dark specks, probably the acid 

 was too strong, or too much was used, or the heat was too great. 



Always keep the acid bottle closed when not in use or the acid 

 will lose strength. Remember that it is a poison and corrosive. 



Points to be Especially Noted in Making the Babcock Test. 1 (1) Be 

 sure to mix the sample of milk thoroughly before drawing it out with 

 the pipette. 



(2) When measuring a sample of milk with the pipette, keep the 

 index finger dry. 



(3) When measuring a sample of milk, keep the mark on the pipette 

 on a level with the eye. The same precaution should be observed 

 when reading the per cent of fat after the test is completed. 



(4) Do not try to measure a sample of milk by trying to draw the 

 milk just to the mark on the pipette. Draw the milk above the mark, 

 as directed. 



(5) W r hen adding milk or acid to the test-bottle, slant the bottle. 

 The liquid will then run down the lower inside of the neck of the bottle, 

 and will not be forced out by outcoming air. 



(6) Do not hold the bottle so that its mouth points toward your- 

 self or any one else. The action of the acid upon the milk produces 

 great heat. This heat often causes the contents of the bottle to spurt 

 out violently. 



A H. E. Ross in Cornell Rural School Leaflet 



