LEFF.MAXN'S FAT DETEEMIXATIOX 213 



[The Lf;ffmau)i-Beam method (sometimes, improp- 

 erly, failed the Beimling test) was worked out in ad- 

 vance of the Gerber test, which resembles it. The fol- 

 lowing description is from Leffmann : ^^ "The dis- 

 tinctive 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 li(iuid in which it is suspended, 

 and thus ]»romote 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 'M) c.c. 

 and are provided with a graduated neck, each division 

 of which represents 0.1 per cent., bv weight, of butter 

 fat. 



" Fifteen c.c. of the milk are measured into the bot- 

 tle, .3 c.c. of a mixture of e(|ual parts of aiiiyl-alcohol 

 and strong hydrochloric acid added, mixed, the bottle 

 filled nearly to the neck with concentrated sulphuric acid, 

 and the liquids mixed by holding the bottle l)y the neck 

 and giving it a gyratory motion. The neck is now filled 

 to about the zero point with a mixture of sulphuric 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 Ite made, the equilibrium of the machine is 

 maintained ))y means of a test bottle, or bottles, filled 

 with a mixture of ecjual parts of sulphuric acid and 

 water. After rotation for from one to two minutes, the 

 fat will collect in the neck of the bottle and the percent- 

 age 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 



■''■■' Henry Luffmann, Atmlysis of Milk and Jlilk Products. Phila- 

 delphia, 10(15. 



