42 



Testing Milk and Its Products. 



generally sufficient to remove all grease and dirt, as 

 well as acid solution from the inside of the bottles. 

 The apparatus shown in fig. 13 will be found convenient 

 for this purpose. After the bottles have been rinsed a 

 second time, they may be placed in an inverted posi- 

 tion to drain, on a galvanized iron rack, as shown in 

 fig. 14, where they are kept until needed. The outside 



of the bottles should 

 occasionally be wiped 

 clean and dry. 



47. The amount of 

 unseen fat that clings 

 to test bottles used 



FIG. 14. Draining-rack for test bottles. for testing milk or 



cream, is generally not sufficient to be noticed in test- 

 ing whole milk, but it plays an important part in test- 

 ing samples of separator skim milk. It may be readily 

 brought to light by making a blank test with clean 

 water in bottles used for testing ordinary milk, which 

 have been cleaned by simply draining the contents and 

 rinsing once or twice with hot water; at the conclusion 

 of the test the operator will generally find that a few 

 drops of fat will collect in the neck of the bottles, some- 

 times enough to condemn a separator. 



Boiling hot water will generally clean the grease from 

 glassware for a time, but all test bottles should, in ad- 

 dition, be given an occasional bath in some weak alkali 

 or other grease-dissolving solution. Persons doing con- 

 siderable milk testing will find it of advantage to pro- 

 vide themselves with a small copper tank, fig. 15, 

 which can be filled with a weak alkali-solution. After 



