180 AGRICULTURE. 



and are run by steam-power. The bottles 

 should always be arranged so that the machine 

 will be balanced before running- it. 



The speed at which these machines are to be 

 run depends upon the size of the revolving 

 wheel, but the rim should, as a rule, move from 

 60 to 70 feet per second. 



(5) Sampling Milk. — In testing milk the 

 greatest care is necessary to get a fair sample 

 of the lot to be tested. The entire amount 

 should be poured from one vessel to another 

 several times if possible, or, if this cannot be 

 done, it should be stirred thoroughly from top 

 to bottom. Many errors are made by not secur- 

 ing the correct average sample. 



(6) Making the Test. — {a) Mix the milk thoroughh', 

 and measure sample into test-buttie. (l>) Add measure 

 of acid by pouring carefully down side of bottle held at 

 slight angle from perpendicular.* (r) Mix thoroughly 

 by shaking with a rotary motion until the liquid be- 

 comes an even chocolate brown color. (^/) Run in a 

 centrifugal machine five minutes at correct speed. (<?) 

 Stop and fill to base of neck with hot water or distilled 

 water, 150" F. or above. (/) Whirl 3 minutes, then fill 

 with hot water to 7 or 9 per cent. mark, (g) Whirl 2 

 minutes and make reading. 



(7) Reading the Test. — Care must be taken 

 to keep the contents of the test-bottle hot and 

 the fat entirely liquid. It is at times necessary 



* Care should be taken not to allow the acid to come in contact 

 with the fingers or clothing. 



