238 DOMESTIC ANIMALS, DAIRYING, ETC. 



in the milk. For practice, one learning to make the test may figure 

 the pounds of fat in 



25 pounds of milk testing 5.0% fat. Ans. 1.25 pounds of fat 



37 pounds of milk testing 4.0% fat. Ans. 1.48 pounds of fat 



70 pounds of milk testing 3.5% fat. Ans. 2.45 pounds of fat 



Cleaning the Test Bottles. Having read and recorded the per 



cent of fat from each test bottle, empty all of the bottles while still 



hot, and wash them thoroughly, using hot water and soda, washing 



powder, or soap, if necessary, to remove all of the fat. Finally rinse 



with clean water. Small specks left sticking to the inside of the 



neck can be removed with a brush such as is sold for the purpose or 



with a bit of cloth fastened to the end of the stick. 



The Appearance of the Fat Column. The color of the fat col- 

 umn at the end of the test should be light brown. If acid is added 

 when the milk is too warm, as when fresh from the cow, or if it is 

 too strong, or if too much is used, the fat column may be very dark, 

 or may contain black particles of curd which interfere with accurate 

 reading. Incomplete mixing or delay in mixing acid and milk may 

 cause similar trouble. In such cases the bottle must be washed and 

 the test repeated. The milk and acid should be at about 70 degrees 

 to get the 'best results, and if this is the case and the fat is still black, 

 a little less acid should be used in repeating the test. It is a good 

 plan to add the acid from the little measuring cylinder in several por- 

 tions, shaking well after each addition. If the acid is of the correct 

 strength, i. e., about 90 per cent pure, of specific gravity 1.82, as 

 usually sold for use in the Babcock test, no trouble will be had. 



Sometimes the fat column contains white or light colored par- 

 ticles resembling curd, at the end of the test, and in such cases the 

 acid used is too weak, or the amount used is too small, or the milk 

 and acid are too cold when mixed, as may occur in the winter time. 

 Hard water sometimes causes bubbles of foam at the top of the fat 

 column. To avoid this, use soft water in testing. 



Sampling and Testing Milk of Different Cows. In comparing 

 the amounts of butter fat produced by different cows, it is necessary 

 to weigh and test the milk regularly throughout the season. The 

 testing and weighing may be done once a month, twice a month, 

 weekly, or daily. Or the milk may be weighed daily, and tested as 

 often as convenient. 



Testing Skim Milk by the Babcock Test. Wherever cream is 

 sold the skim milk should be tested for fat occasionally, to make sure 

 that the cream separation is complete. To test skim milk, collect 

 the entire quantity of skim milk running from the separator in a 

 tub or barrel, mix it well by stirring. While the skim milk is still 

 in motion, measure with a pipette 17.6 cc. of milk, avoiding the 

 foam, into a special form of Babcock test bottle called a skim milk 

 bottle. Add acid and whirl at full speed for a few minutes longer 

 than usual, and keep the bottles hot, since it is hard to get out all of 

 the fat in testing skim milk. 



The ordinary milk test bottle reading 10 per cent on the scale 

 cannot be used for testing skim milk, because the column of fat 



