in CHEESE 189 



behind, and the weight of fat left in the flask after the evapora- 

 tion of the ether-benzene is multiplied by 100, which gives the 

 percentage amount of fat in the sample of cheese. 



(b) PRACTICAL METHODS. 



Gerber s Test. 



Gerber's acid butyrometer test (p. 69) can also be used for 

 the determination of fat in cheese when the results do not 

 require to be scientifically correct. The method worked out by 

 Gerber is not as good as the modification proposed by Siegfeld, 1 

 so the latter only will be described here. 



About 2*5 grams of cheese are weighed out into a small flask 

 and dissolved in 10 c.c. of sulphuric acid (sp. gr. T5) by warming 

 over a naked flame and shaking. Solution having been effected, 

 the contents of the flask are transferred by means of a small 

 funnel, the lower end of which is cut off obliquely, into a Gerber 

 tube. The flask and funnel are washed out with small quantities 

 of the same acid until the volume of the liquid is 21 c.c. It is 

 advisable to have a special mark on the butyrometer tube for this 

 purpose. One c.c. of amyl alcohol is then added, the tube shaken 

 and warmed in a water-bath to 60-70 C., again shaken and 

 finally whirled in the centrifuge for 5-6 minutes. When the 

 tube is taken from the centrifuge it is again placed in the water- 

 bath, after which the column of fat can easily be read off. A 

 simple calculation is necessary, for the scale of the milk butyro- 

 meter is graduated for 11 c.c. milk ; which is equivalent to 

 11 '33 g., if the specific gravity of milk be taken as T03. All 

 that is required is to multiply the percentage of fat by 11'33 

 and divide by the weight of cheese taken. This is expressed by 

 the formula: 



, _ p. 11-33 

 J ' /,- 



where/ = the percentage of fat in the cheese, 

 p = the percentage of fat read off, 

 k = the weight of cheese taken. 



With skim milk cheese Gerber's method gives unreliable 



1 Mll<'h-Z<itii,Kj, 1904, No. 28. 



