THE BABCOCK TEST 



63 



before the reading is made. This usually needs to be 

 done in cold weather, when hand-testers are used, 

 especially if no hot water has been placed in the jacket 

 during the whirling. If the fat is above 150° F., it 

 should be allowed to cool to 140° F. or below before 

 reading the results. Too high temperatures give too 

 high results, because the fat-column expands. 



(3) The line of division between the fat-column and 

 the liquid beneath is nearly a straight line when the 

 testing is properly done, and one need have no doubt 

 about the reading of the scale at this point. But the 

 upper surface of the fat-column is 

 concave instead of straight, which 

 may cause some uncertainty as to the 

 exact point at which the reading 

 should be made on the scale. The 

 correct reading is taken at the line 

 where the upper surface of the fat- 

 column meets the sides of the neck, 

 the very highest point at which the 

 fat-column is seen. The reading 

 should not be made from the dark 

 line or meniscus lower down, which 

 is caused by the refraction of the 

 curved surface. The points at which 

 the readings should be made are shown 

 in Fig. 27, indicated as A and B. 

 Results read this way agree with those 

 obtained by gravimetric analysis. The 

 objection may be raised that we get too high results 

 by reading from the extreme top points of the fat- 

 column, just as if the upper surface were straight at 



FIG. 2"] 



MEASURING 



FAT-COLUMN 



