16 MILK ANALYSIS 



and public exhibition all the rapid centrifugal methods except 

 the De Laval, is sometimes called the "Beimling" method, 

 but Beimling was merely a patentee of a crude form of cen- 

 trifugal machine, and had no part in devising the mixture for 

 freeing the fat. The distinctive feature is the use of fusel oil, 

 the effect of which is to produce a greater difference in surface 

 tension between the fat and the liquid in which it is suspended, 

 and thus promote its readier separation. This effect has been 

 found to be heightened by the presence of a small amount of 

 hydrochloric acid. 



The test-bottles have a capacity of about 30 c.c. and are 

 provided with a graduated neck, each division of which repre- 

 sents o.i per cent, by weight of butter fat. 



15 c.c. of the milk are measured into the bottle, 3 c.c. of a 

 mixture of equal parts of amyl alcohol and strong hydro- 

 chloric acid added, mixed, the bottle filled nearly to the neck 

 with concentrated sulfuric acid, and the liquids mixed by 

 holding the bottle by the neck and giving it a gyratory mo- 

 tion. The neck is now filled to about the zero point with a 

 mixture of sulfuric acid and water prepared at the time. It 

 is then placed in the centrifugal machine, which is so arranged 

 that when at rest the bottles are in a vertical position. If only 

 one test is to be made, the equilibrium of the machine is main- 

 tained by means of a test-bottle, or bottles, filled with a mixture 

 of equal parts of sulfuric acid and water.. After rotation for 

 from one to two minutes, the fat will collect in the neck of the 

 bottle and the percentage may be read off. It is convenient to 

 use a pair of dividers in making the reading. The legs of these 

 are placed at the upper and lower limits respectively of the fat, 

 allowance being made for the meniscus; one leg is then placed 

 at the zero point and the reading made with the other. Ex- 

 perience by analysts in various parts of the world has shown 

 that with properly graduated bottles the results are reliable. 

 As a rule, they do not differ more than o.i per cent, frorn. 



