A DAIRY LABORATORY GUIDE 5 



THE BABCOCK TEST 



The Babcock test is a test for the per cent of fat 

 in milk and its products. It was invented by Dr. 

 S. M. Babcock, chief chemist for the experiment sta- 

 tion at Wisconsin, and a description of the test was 

 published in a report of 1890 from that station. 

 The instrument used to measure the milk is called 

 a pipette and holds up to its graduated mark 17.6 

 cc. Since milk is somewhat viscous, the pipette 

 will deliver on an average 17.44 cc, which is for 

 all practical purposes 18 grams. In using the 

 pipette the milk is drawn above the 17.6 cc. mark 

 and the soft part of the index finger placed quickly 

 over the pipette. The column of milk can be 

 easily controlled and allowed to flow out until it is 

 on a level with the 17.6 cc. mark. The pipette 

 should always be held so that the 17.6 cc. mark is 

 on a level with the eye. The sample to be tested 

 is measured into a special bottle with a graduated 

 neck, holding a column of melted fat which is a 

 definite per cent by weight of the 18 grams of milk 

 taken. In adding the milk to the bottle the latter 

 should be held in a slanting position, so that the 

 milk will run down the lower inside of the bottle 

 neck and will not be forced out by the outcoming 

 air. 



After measuring the milk into the bottle, 17.5 

 cc. of sulphuric acid (H2SO4) of a specific gravity 

 of 1.82 to 1.83 is added and the milk and acid at 

 once thoroughly mixed. The acid burns up (by 

 moist combustion) everything in the milk except- 

 ing the fat. The same precautions should be ob- 

 served in adding the acid as in adding the milk, 

 namely, to slant the bottle, and the bottle should be 

 revolved as the acid is poured in, so that all of 



