PHYSICAL AND CHEMICAL EXAMINATION OF MILK 157 



fat should remain warm and should be shaken frequently until the 

 alcohol is saturated with butter. 



In carrying out the Babcock test the procedure is as follows: 



1. Mix the sample. If lumps of fat appear on the surface 

 heat the milk to about 100° F. to melt the fat. 



2. Measure 17.6 c.c. of the sample in a Babcock pipet. The 

 milk should flow into the bottle without loss. This is done by 

 inchning the bottle and allowing the milk to flow down the side 

 of the neck. 



3. Measure in the graduate 17.5 c.c. sulphuric acid. Pour 

 the acid slowly down the inside of the neck to avoid choking the 

 opening. 



Fig. 44. — Reading of percentage of fat by using dividers. (Bull. No. 202, Nov., 

 1914, Agri. Exp. Sta. of Colorado Agri. College.) 



4. Mix the acid with the milk by a rotary motion (Fig. 43). 

 The fluid becomes yellow, turning darker until a dark brown has 

 been reached. Allow to stand for a few minutes and then mix again. 



5. Place the bottles in a centrifuge and whirl for four or five 

 minutes. 



6. After the centrifuge has ceased revolving, add enough hot 

 water to bring the fat into the lower part of the neck and whirl 

 again for two minutes. 



7. Add more water to bring the fat column within the gradua- 

 tion of the neck and whirl again for one or two minutes. 



8. Read the percentage of fat at a temperature of 120° to 130° 

 F. by counting the dividing lines between the top and bottom of 

 the fat column. The use of dividers facilitates correct reading. 

 After the dividers have been spread to measure the distance from 

 the top to the bottom of the fat column, place one point exactly on 

 zero of the graduation and measure the length of the column 

 (Fig. 44). 



