212 



MILK HYGIENE 



celerate the motion three times, by drawing the strap. 

 [With some patterns of centrifuge, those that have a 

 velocity of 800 to 1000 per minute, the whirling is com- 

 pleted in 3 to 4 minutes.] After centrifuging, the bottle 

 is taken out and placed in a water bath at 60 C. (140 

 F.). The fat forms a clear layer in the top of the tube. 

 Through shifting the stopper, the lower border of the 



Fro. 22. 



Test bottles and pipettes used in connection with Gerber s method for fat-determination. 



fat layer can be brought into the same plane with one of 

 the division lines and the thickness of the layer of fat 

 can be read off. One should read from the lower part 

 of the curved upper line. The upper, narrow part of 

 the tube is divided in 90 parts, each line corresponds to 

 0.1 per cent, fat; for example, if the fat layer reaches 

 line 35, then the fat content of the milk is 3.5 per cent. 



