1&2 ILiLINOIS STATE DAIRYMEN'S ASSOCIATIOiN. 



top, and that a fair sample is one in which the fat is evenly 

 distributed throughout the whole sample. It should also be 

 remembered that in mixing a sample of milk for testing, the 

 fat has a tendency to separate or to be churned out by any 

 violent agitation during its mixing. 



SOME MILK-TESTING DIFFICULTIES. 



As perviously stated, the dairy student often finds that 

 although he may have tested milk at factories for some time, 

 he has not detected the cause of certain difficulties that he 

 may have met with in his work. A little investigation in milk- 

 testing will often show that, as in other departments of 

 science, there is always a cause for an effect. 



A correct graduation of the neck of the test bottle in 

 which the fat is measured, and the exact measuring of the 

 milk with a pipette of proper capacity are two of the funda- 

 mental principles of accurate milk-testing. The necessity of 

 these two standards being exact is so obvious that their dis- 

 cussion is superfluous. These points should be forgotten, how- 

 ever, in case there is a disagreement in the results obtained by 

 two operators. 



Assuming that the glassware has been correctly made, the 

 next point worthy of inspection is its cleanliness. The film of 

 grease that clings to glassware becomes most apparent in test- 

 ing samples of very thin skim milk. Before testing a sample 

 of skim milk it is often instructive to make a complete test of 

 a sample of clean water. The operator often finds that a 

 few drops of fat will collect in the neck of /the bottle and 

 that this is sometimes enough to condemn a separator, al- 

 though the water which has been tested has not been near a 

 separator. The natural and proper inference for such a test 

 is, that either the pipette or the test bottle had not been 

 thoroughly cleaned of every trace of fat before they were 

 used. 



The unseen fat that clings to glassware is generally not 

 sufficient to be noticed in the results obtained by testing dif- 

 ferent samples of whole milk, but in skim milk testing it 

 plays quite an important part. Boiling hot water will gen- 

 erally clean the grease from glassware for a while, but all 



