METHODS OF EXAMINING MILK 



239 





power machine making 800 to 1000 revolutions per min- 

 ute 3 to 4 minutes is sufficient. When the bottles are 

 removed from the centrifuge they should be submerged 

 in an upright position, with the stopper downward, in 

 a water bath at 60 C. (140 F.) until the reading is 

 taken, unless the samples are so few that they can all be 

 read in a few seconds. The fat collects in 

 a clear, yellow column at the top of the 

 fluid in the neck. The stopper is turned 

 sufficiently to bring the lower border of 

 the fat column on a level with one of the 

 main divisions of the scale and the per 

 cent, of fat is then read off. The read- 

 ing is taken from the bottom of the fat 

 column to the lower border of the menis- 

 cus at the top. After the reading is taken 

 the bottle should be emptied at once and 

 cleaned as directed for the Babcock bottle. 



A special bottle is made for testing 

 cream. The cream placed in the bottle is 

 weighed; otherwise the per cent, of fat in 

 cream is determined in the same manner 

 as that in milk. 



Lactoscope Test. It was proposed 

 some time ago to determine the per cent. 



FIG. 37. Feser's 



of fat in milk by measuring its transpar- iactosco pe . 

 ency. Several forms of apparatus have been devised for 

 this purpose, the simplest being Feser's Iactoscope (Fig. 

 37). This is a glass tube, contracted towards the bot- 

 tom. A vertical white-glass column, which is encircled 

 by six blaek horizontal lines, projects upward into the 

 contracted part. On the surface of the upper part of the 

 tube there is a graduated scale with a column of figures 



