GERBER METHOD 67 



Leffmann-Beam Process. 15 c.cms. of the sample are 

 transferred by means of a pipette into a flat-bottomed bottle 

 provided with a narrow neck graduated into 80 divisions, 10 of 

 which correspond to 1 per cent of fat by weight. 9 c.cms. of 

 concentrated commercial sulphuric acid are then added in three 

 portions with thorough admixture after each, and finally, 

 3 c.cms. of a mixture of equal volumes of concentrated hydro- 

 chloric acid and amyl alcohol. After shaking, the bottle is 

 filled to the zero mark with hot dilute sulphuric acid (1 in 2) 

 and whirled in the centrifuge for 3 to 4 minutes. The fat rises 

 to the top of the liquid as a yellowish coloured layer and the 

 percentage is read off by deducting the reading at the junction 

 of the fat and acid from the reading at the extreme top of the 

 fat, not the bottom of the meniscus. 



Babcock Method. This method differs from the Leffmann- 

 Beam process in but a few details. The bottle neck is divided 

 into 50 divisions each representing 0.2 per cent of fat by weight 

 of the 17.6 c.cms. employed. The procedure is as follows: 

 the milk having been placed in the bottle 17.5 c.cms. of com- 

 mercial sulphuric acid are gradually added with constant agi- 

 tation until the caseinogen is dissolved. The bottle is then 

 placed in a centrifuge and whirled for four minutes at 600 to 

 1200 revolutions per minute, according to the diameter of the 

 machine; hot water is added until the bottle is filled to the 

 lower end of the neck, whirled for one minute, then filled to the 

 zero mark with hot water and whirled for one further minute 

 to bring the fat layer into the graduated neck. The per- 

 centage of fat is then read off as in the Leffman-Beam method, 

 care being taken that all readings are made between 130 and 

 150 F. when the fat is quite liquid. The author has found that 

 the indistinct line of demarkation between the fat and the acid 

 occasionally found with this process can be obviated by the 

 addition of 1 c.cm. of amyl alcohol after the addition of the acid. 



Gerber Method. This differs from the modified Babcock 

 described only in the size and type of bottle, and quantities of 

 acid and milk employed. 11 c.cms. of milk, 1 c.cm. of amyl 



