346 



ELEMENTS OF AGRICULTURE 



After all the samples of milk to be tested have been measured, 

 the acid should be added. Fill the acid measure to the 17.5 cc. mark 

 with acid that is neither very cold nor hot. Pour this into the bottle 

 with the milk, holding the bottle in a 

 slanting position. The acid will then carry 

 down any milk left in the neck and follow 

 the glass surface to the bottom of the bot- 

 tle and form a layer under the milk. 



Hold the bottle by the neck and give it 

 a circular motion for a few minutes, mix- 

 ing the milk and acid until no milk or 

 clear acid is visible (Fig. 177). By this 

 time, the contents will be dark-colored 

 and hot. This change is clue to the acid 

 dissolving all 



FIG. 176. Putting the milk 

 into the test bottle. The pi- 

 pette is held at an angle with 

 the test bottle and its point 

 against the inside of the neck. 



FIG. 177. Mixing milk and 

 acid. A rotary motion with 

 the bottle not pointed toward 

 the face. 



the solid constituents of the milk except 



the fat, which it does not affect. 



Whirling the Bottles. The bottles are 



whirled to separate the fat so that it can 



be measured. They should be hot when 



whirled. If necessary, they may be heated 



by standing in hot water before being 



put into the machine. A steam machine 



is easily kept hot when in use. Other 

 kinds should have 

 boiling hot water placed in them. 



Place the bottles in the machine so that each 

 one will have another directly opposite, to keep 

 the machine in balance. Whirl the bottles five 

 minutes at the proper speed for the machine in 

 use (Fig. 178). Then stop it, and, with the 

 pipette or other convenient means, add hot water 

 to each bottle until the contents come up to the 

 bottom of the neck. Whirl two mintues. Add 

 hot water enough to bring the top of the fat 

 nearly to the top of the graduations on the neck 

 of the bottles. Whirl one minute. The fat should 



then form a clear column in the neck of the bottle. 



Reading the Percentage. Keep the fat warm so that it will be in a 



fluid condition. Hold the bottle by the upper end of the neck, letting 



FIG. 178. 

 Whirling the samples 



