24 DAIEY CHEMISTRY 



bottle g. The automatic pipette is fastened to an 

 iron stand dd, which rests upon the table. Other 

 forms of apparatus are also in use. In ordinary 

 practice a strong glass vessel with a good lip for 

 pouring is the most satisfactory arrangement for 

 handling the acid. A white tile is excellent to have 

 on the table under the acid bottle. 



23. Composite Sample. In actual creamery prac- 

 tice the daily testing of each patron's milk, or in the 

 dairy, the testing of both morning's and evening's 

 milk from each cow is too expensive. To obviate 

 this daily testing, a composite or compound sample 

 is made up by saving a small sample of each milk in 

 a pint fruit can. At the end of one week or of two 

 weeks the compound sample is carefully mixed and 

 tested. Inasmuch as this test represents a propor- 

 tional part of each lot of milk, it gives the average 

 amount of fat in the milk for the period. In cream- 

 eries and factories, where milk is paid for by test, 

 the composite test when properly carried out gives 

 good results. 



The composite sample should be kept covered so 

 that the surface of the cream will not become dry 

 and leathery. The sample should also be kept in a 

 cool place to prevent fermentation. 



Various chemicals are used to keep the milk fresh. 

 Potassium bichromate has been found to give the 

 best satisfaction. About one half gram of potassium 

 bichromate will be sufficient to preserve a pint of 

 milk. Winton and Ogden state that a .22 pistol 



