336 PRODUCTIVE FARMING 



Let this milk flow gently down the long neck into the 

 test bottle, M. Do not spill any. Blow in the last drop. 

 The steps thus far are the most particular and should be 

 practised with water a few times or until the work can be 

 done well. Always make the test in duplicate to avoid 

 error, using two bottles. 



Adding the Add must be done carefully. Be ready to 

 wash up any spilled acid quickly, as its burns are serious. 

 Use water freely and add soap or soda if needed. The acid 

 is measured up to the 17.5 cc. mark, in the little cylinder 

 or acid measure, A. Pour it into the milk sample in the test 

 bottle, holding the bottle in a slanting position to let the 

 acid pass by the outgoing air. 



Mixing the milk and acid is now done by holding the 

 bottle by the neck and giving it a circular motion for a few 

 minutes. Do not point the mouth towards yourself nor 

 any one else. Mix until the contents are dark colored 

 throughout. The action of the acid makes it very hot. 



Whirling. — Place the test bottles in the whirling machine 

 in pairs, directly opposite each other, to perfectly balance 

 the machine. The speed to run the machine depends on its 

 diameter and is usually marked on the machine. Run it 

 five minutes. Stop and add hot water to fill each test bottle 

 up to the bottom of the neck. Whirl two minutes. Add 

 hot water to bring the top of the fat nearly to the top of the 

 scale (graduation) on the neck. Whirl one minute. During 

 all the whirling and the reading the test bottles must be 

 kept hot by putting hot water into the machine under the 

 bottles. 



Reading the Result. — Take the bottle by the top of the 

 neck and hold the scale level with the eye. Read the marks 

 at the extreme top and bottom of the fat. The difference 

 between these is the percentage of fat in the sample. For 

 example, if the bottom reads 3 . 2 and the top reads 7 . 4 the 

 percentage of butter fat would be the difference, or 4.2. 



