THE BABCOCK TEST 49 



a reading, because of the expanded condition of the fat, 

 while too low a temperature gives an uncertain reading. 

 Precautions in Making a Test. i. Be sure you have 

 a fair sample. 



2. The temperature of the milk should be about 60 

 or 70 degrees. 



3. Always mix twice after acid has been added. 



4. Be sure your tester runs at the right speed. 



5. Use nothing but clean, soft water in filling the 

 bottles. 1 



6. Be sure the tester does not jar. 



7. 'Be sure the acid is of the right strength. 



8. Mix as soon as acid is added to milk. 



9. Do not allow the bottles to become cold before 

 reading the test. 



10. Read the test twice to insure a correct reading. 

 The water added to the test bottles after they have been 



whirled should be clean and pure. Water containing 

 much lime seriously affects the test. Such water may 

 be used, however, when first treated with a few drops of 

 sulphuric acid. 



As stated before, skim-milk, buttermilk, and cream are 

 tested in the same way as milk, with the, exception that 

 the cream sample is weighed, not measured. (See p. 51.) 



Testing Cream. Accurate tests of cream cannot be 

 secured by measuring the sample into the bottle as is 

 done in the case of milk. The reason for this is that 

 the weight of cream varies with its richness. The richer 

 the cream the less it weighs per unit volume. This is illus- 

 trated in the following table by Farrington and Woll : 



