152 STATE BOARD OP AGRICULTURE. 



Hold the test bottle in the left hand, also slightly inclined so that the 

 milk will run down the side of the neck of the bottle. This lets the air 

 escape as the milk goes in. Wait a second or two for the pipette to drain, 

 then blow out the last drop before removing from the bottle neck. 



Our plan is to throw away the first sample drawn into the pipette from 

 each lot of milk, the second sample being used, if exactly 17.6 cubic centi- 

 meters are indicated when the pipette goes into the test bottle. This 

 may make but a slight difference, but it helps secure that accuracy so 

 essential to a perfect test for butter fat. When we made our first tests 

 we practiced for some time in taking samples of water with the pipette. 

 It was quite diflQcult to secure a perfect sample of water, but by some 

 practice we readily succeeded. 



ADDING THE ACID. 



The most important part of the work is done when a correct sample of 

 milk is placed in each test bottle. The sulphuric acid may be imme- 

 diately added and the test completed, or several days may elapse before 

 this is done. When this is done and the milk becomes coagulated, the 

 curd should be broken up before adding the acid. 



Be sure to use fresh acid, if possible, having a tested specific gravity 

 of 1.82 to 1.83. Add 17.5 cubic centimeters to each sample of whole milk. 

 This is approximately using equal portions of both milk and acid. If 

 there is a slight variation in the amount of the acid used, of the above 

 specific gravity, it will not materially affect the result. 



When the acid is of greater strength, or too much is used, the fat itself 

 is attacked. If the acid is too weak, or not enough used, the casein is not 

 all held in solution during the process of testing. 



WATER TO BE USED. 



We use rain water, whenever possible, and have it boiling hot. When 

 we have used well or hard water it usually makes more or less difficulty 

 in reading the per cent of fat with the accuracy required. The carbonate 

 of lime in hard water sets free more or less carbonic acid, thus causing 

 considerable foaming and bothers the correct finding of the top of the fat 

 column in the bottle neck. Hard water, however, may be improved by 

 boiling. 



As soon as the acid is added, by turning into the bottles, held in an 

 inclined position, so as to run down the side of each bottle, the contents 

 must be shaken gently with a rotary motion. At first there is a precipita- 

 tion of curd from the milk, but this soon dissolves. A large amount of 

 heat is involved by the chemical action. When the whole contents 

 change to a dark brown color the bottle may be placed in a pocket of 

 the tester head. 



The test must now be comjjleted as soon as possible. A tester having 

 an even number of bottles is to be preferred. Place the bottles in pairs 

 in the head so as to maintain an equilibrium during the whirling jjrocess. 

 Place the cover on the jacket and whirl with a steady, even motion for at 

 least five minutes, keeping up the required speed given in the directions 

 sent out with each machine, of whatever pattern. 



