f2 MAINE AGRICULTURAL EXPERIMENT STATION. 



and the second set can stand while the first is being whirled. 

 It is much better to make 12 tests at a time than to make a 

 larger number. Twelve are about all one can easily read before 

 the fat begins to cool and contract in volume. 



Precautions. That good results and clear separations can be 

 obtained by the previously described modifications, the writer 

 and others connected with the College have fully demonstrated. 

 It is necessary, however, that certain details be strictly observed 

 to attain success, and to make those points more prominent 

 they are repeated as precautions. 



The acid must be of the proper strength: 1.82 specific gravity 

 at 60" F.j is more universally successful than a stronger acid, 

 though 1.825 may be used in some cases. With very rich milk, 

 20 to 21 cubic centimeters of acid of 1.82 specific gravity works 

 much better than a smaller quantity of stronger acid, probably 

 because there is less water in rich milk to properly dilute the 

 acid than in poor milk. Rather thin milk will give good results 

 with acid of quite varying strength. If the acid is too strong, 

 the fat will be blackened, or black particles will appear in the 

 lower part of the fat column. If the acid is not strong enough, 

 the fat will appear cloudy, and white particles of curd will collect 

 at the lower part of the column so that an accurate reading can- 

 not be made. 



The milk should not be colder than 70 : F.. or warmer than 80 3 

 F. when the acid is added. If the milk is too cold, the curd will 

 not all be dissolved in the time allowed, and the fat will appear 

 cloudy with white particles in the lower part of the column 

 which will interfere with the reading. If the milk is too warm, 

 the action of the acid will be too violent, the fat will be burned, 

 and the whole column appear blackened; or if only slightly 

 burned, black particles will appear in the lower part of the 

 column. 



The acid and milk must be thoroughly mixed together and 

 the mixture stand not less than 5 minutes before hot water is 

 added; otherwise a clear separation will not be obtained. It 

 is also best to shake the bottle again slightly, just before adding 

 the hot water, to dissolve any particles of curd that have risen 

 with the fat. 



