386 MILK AND ITS PRODUCTS 



1) Get milk near 60 F. ; mix thoroughly by pouring from vessel 

 to vessel. 



2) Fill pipette to the mark with milk. 



3) Empty pipette in test bottle. 



4) Fill the acid measure to the mark, and pour the acid into the 

 test bottle, washing down any milk hanging to the neck. 



o) Shake test bottle at once until the solution has a coffee color. 



6) Place an even number of test bottles in the pockets of the 

 machine and whirl five minutes. 



7) Add hot water (hot enough to make the fingers uncomfortable) 

 up to the neck of the bottles. 



8) Whirl one minute. 



9) Add hot water up to mark 7 or 8 on stem. 



10) Whirl one minute. 



11) Read the fat column at the temperature of about 130 F. 



There are many details in successful milk testing, which 

 can be mastered by observing the operation in a dairy. 

 Manufacturers of machines, too, inclose minute directions 

 with every outfit they sell. Only a few precautions are 

 given here : 



Do not get any acid on your fingers, or allow it to drop 

 on the floor. If some should fall on the woodwork of 

 the schoolroom, or get on the hands, wash with water at 

 once. Practice is needed in using the pipette. Be sure 

 the finger is dry, when allowing the pipette to drain to 

 the mark. In a small machine, especially in cold weather, 

 it may be necessary to fill the jacket on the outside of the 

 bottles with hot water. Each division on the stem of the 

 test bottle equals 0.2 per cent fat, but heat expands and 

 cold contracts this column. If white cheesy particles ap- 

 pear below the column of fat, the acid may have been too 

 weak or too little in quantity, or the milk may have been 

 too cold or not properly mixed with the acid. If black 

 particles appear, some of the opposite conditions must 

 have been present in too high a degree. White bubbles 

 at the top show that the water was too hard. All glass- 



