646 ANNUAL REPORT OF THE Off. Doc. 



plcU-ed over the iipiiei* end of the piijette before the milk ruus down 

 below the mark. A little practice will be required to do this. By 

 lightening the pressure of the finger on tiie end of the pipette, the 

 milk is allowed to flow out until it just reaches the marlc on the 

 stem. If the pipette is correctly made, the quantity of milk in 

 the pipette is just 17.(> cubic centimeters. 



81. Ruoning Milk Sample into Test Bottle. 



Having the pipette containing just IT.G c. c. of milk, we now hold 

 the pipette obliquely, placing its point in the neck of the test bottle 

 and the milk is allowed slowly to flow down the inside of the neck. 

 Not a drop of milk should be lost in (his operation. The portion of 

 milk remaining in the point of the pipetie is removed by blowing 

 through the pipette before removiiig it from the test bottle. The 

 pipette should never be held perpendicularly straight over the test 

 bottle, running the milk straight down in, since the neck may choke 

 up with milk and run over the top. 



82. Adding Acid to Milk in Test Bottle. 



(1.) Strength of Sulphuric Acid for Test. — The sulphuric acid to 

 be used in the Babcock test must have a strength corresponding to 

 a specific gravity not below 1.82 or above 1.83. If the acid is 

 stronger, the fat in the final part of the test will be dark in color and 

 its amount hard to read. If the acid is weaker than 1.82, there is 

 danger of some casein remaining undissolved and this will mingle 

 with the fat and make the test unsatisfactory. It is possible to 

 secure good results with strong acid by using somewhat less, but 

 it is best to purchase acid of just the right strength. The sulphuric 

 acid should be kept in bottles tightly stoppered with glass stoppers, 

 because it rapidly absorbs moisture and becomes too weak in time if 

 exposed to the air. 



(2.) Caution in Haudling Acid. — If, in handling, sulphuric acid 

 gets on the skin anywhere it should be immediately and thoroughly 

 washed with abundance of water. Too great care cannot be exer- 

 cised in handling this acid. 



(8.) Measuring Acid and Adding to Milk. — When one has the 

 samples of milk ready in the test bottles, then the acid measure is 

 filled to the 17.5 c. c. mark, and from this is poured ioto the test 

 bottles. The acid being much heavier than the milk sinks to the 

 bottom of the bottle without mixing, the milk floating on top. Much 

 care should be exercised in pouring the acid into the test bottle 

 containing the milk. This is best done by holding the bottle in an 

 inclined position, so that the acid will follow the inside walls down 



