68 MAINE AGRICULTURAL EXPERIMENT STATION. 



first there is a precipitation of curd, but this rapidly dissolves. 

 There is a large amount of heat evolved by the chemical action, 

 and the solution, at first nearly colorless, soon changes to a 

 very dark brown, owing to the charring of the milk sugar and 

 perhaps some other constituents of the milk or cream. 



Whirling the Bottles. The test bottles containing the mixture 

 of the milk and acid should be placed in the machine, and 

 whirled directly after the acid is added. An even number of 

 bottles should be whirled at the same time, and they should be 

 placed in the wheel in pairs opposite to each other, so that the 

 equilibrium of the apparatus will not be disturbed. When all 

 of the test bottles are placed in the apparatus, the cover is placed 

 upon the jacket, and the machine turned at the proper speed for 

 about five minutes. The test should never be made without 

 the cover being placed upon the jacket, as this not only pre- 

 vents the cooling of the bottles when they are whirled, but in 

 case of the breakage of bottles will protect tne face and eyes of 

 the operator from injury by pieces of glass or hot acid. Man- 

 aged in this way, no extra heat is required, as that caused by the 

 chemical action is sufficient to keep the fat liquid. If the bottles 

 have stood, after the acid is added, until the contents are cooled, 

 they should be warmed to about 200 F. by placing them in hot 

 water before whirling. The machine should be frequently 

 examined to make certain that there is no slipping of belts or 

 frictional bearings which may cause too slow motion and result 

 in an imperfect separation of fat 



Filling the Bottles. As soon as the bottles have been suf- 

 ficiently whirled, they should be filled to near the top of the 

 graduated part of the stem with hot water. If practicable, dis- 

 tilled or rain water should be used for the purpose. The bottles 

 are most easily filled by means of the apparatus described on 

 page 64. If only a few tests are to be made, the water can be 

 added with the pipette or glass cylinder. The cover should then 

 be replaced and the machine turned for about one minute, after 

 which the fat may be measured. 



Measuring the Fat. The fat when measured should be warm 

 enough to flow readily, so that the line between the acid liquid 

 and the column of fat will quickly assume a horizontal position 

 when the bottle is removed from the machine. Any tempera- 



