56 MARKET DAIRYING 
5. Use nothing but clean, soft water in filling the 
bottles. 
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. De 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. 
Cleaning Test Bottles. As soon as the test is read, 
the bottles are emptied by shaking them up and down so 
as to remove the white sediment. Next wash them in 
hot water containing some alkali, and finally rinse them 
with hot water. Occasionally the bottles should be rinsed 
with a special cleaning solution, which is made by dis- 
solving about one ounce of potassium bichromate in one 
pint of sulphuric acid. A small brush should also oc- 
casionally be run up and down the neck of the bottle. 
Testing or Calibrating Milk Bottles. Fill the bottle 
to the zero mark with water, or preferably wood alco- 
hol to which a little coloring matter has been added. 
Immerse the lower section of the tester, shown in Fig. 19, 
in the contents of the bottle. If the bottle is correct, the 
contents will rise to the 5% mark. Next immerse both 
sections of the tester which will bring the contents to 
the 10% mark if the bottle is correctly calibrated. 
