TESTING DAIRY PRODUCTS BY THE BABCOCK TEST. 



69 



=-«3 



ELo 



Fig. 5. 



ture between 110° F. and 150 F. will answer, but the higher 

 temperature is to be preferred. The slight difference in the 

 volume of fat due to this difference in temperature is not suf- 

 ficient to materially affect results. 



To measure the fat, take a bottle from 

 its socket and holding it in a perpendicular 

 position with the scale on a level with the 

 eye, observe the divisions which mark the 

 highest and the lowest limits of the fat. ~~ 

 The difference between these gives the per 

 cent of fat directly. The reading can 

 easily be taken to half divisions or in the 

 ordinary milk bottle to one-tenth per cent. 



The line of division between the fat and 

 the liquid beneath is nearly a straight line <L — 

 and no doubt need arise concerning the 

 reading at this point; but the upper surface 

 of the fat being concave, errors often occur 

 by reading from the wrong place. The 

 reading should be taken at the line where the surface of the fat 

 meets the side of the tube and not from the surface of the fat 

 in the centre of the tube nor from the bottom of the dark line 

 caused by the refraction of the curved surface. For instance in 

 fig. 5 the reading should be taken from a to b and not to c or d. 



The reading may be made with less liability of error by meas- 

 uring the length of the column of fat with a pair of dividers, one 

 point of which is placed at the bottom and the other at the upper 

 limit of the fat. The dividers are then removed and one point 

 being placed at the zero mark of the scale on the bottle used, 

 the other will be at the per cent of fat in the sample examined. 



Sometimes bubbles of air collect at the upper surface of the 

 column of fat and prevent a close reading; in such cases a few 

 drops of strong alcohol (over 90 per cent) put into the tube on 

 top of the column of fat will cause the bubbles to disappear and 

 give a sharp line between the fat and alcohol for reading. 

 Whenever alcohol is used for this purpose, the reading should 

 be taken directly after the alcohol is added, as after it has stood 

 for a time, the alcohol partially unites with the fat and increases 

 its volume. 



