GERBER'S METHOD 



187 



the case of performing the test with a number of 

 samples, be warmed to 60° to 65° C. for a few minutes 

 in the water-bath (Fig. 27) prior to being centrifuged. 

 When the centrifuge is fitted with a heating arrange- 

 ment, this preliminary warming is not necessary. 



Fig. 27. — Water-bath for heating Gerber test-bottles. 



The centrifuge containing one or more test-bottles 

 is then revolved at a speed of about 1000 revolutions 

 per minute for four minutes, the test-bottles removed 

 and placed in the water-bath at 60° to 65° C. for 

 several minutes. By holding the test-bottle in an 

 inverted position and carefully screwing in the rubber 

 stopper, the lower level of the fat column, which is 

 usually of a light yellow colour, is adjusted to the zero 

 mark, and the percentage of fat read off directly on 

 the graduated scale. 



