TESTING DAIRY PRODUCTS BY THE BABCOCK TEST. 6j 



air to escape without clogging the neck, and remove the finger, 

 allowing the liquid to flow into the bottle. After waiting a short 

 time for the pipette to drain, blow into the upper end to expel 

 the liquid held by capillary attraction in the point. If the 

 pipette is not dry when used, it should be first filled with sample 

 to be tested, and this thrown away before taking the test sample. 

 If several samples of the same lot are taken for comparison, 

 the material to be tested should be poured once from one vessel 

 to another after each sample is measured. Neglect of this pre- 

 caution may make a perceptible difference in the results. Per- 

 sons who have had no experience in the use of the pipette will 

 do well to practice a short time by measuring water into a test 

 bottle before attempting to make an analysis. 



Adding the Acid. After the sample has been measured into 

 the test bottle, the test may be proceeded with immediately, or 

 it may be left for a day or two without materially changing the 

 result; samples that have remained in the test bottles two or 

 three weeks, and which had commenced to mould before the 

 acid was added, have given the same amount of fat as samples 

 tested immediately after being measured. If the sample has 

 become coagulated, the curd should be broken up by shaking 

 the test bottle before the acid is added. It is advisable, when 

 possible, that the test be proceeded with immediately after the 

 samples are measured. 



The volume of commercial sulfuric acid required for a test 

 is 17.5 cubic centimeters. If too little acid is added, the casein 

 is not all held in solution throughout the test, and an imper- 

 fect separation of the fat results. If too much acid is used, the 

 fat itself is attacked. The acid need not be measured with great 

 accuracy, as small variations will not affect the results. 



When all of the samples of milk to be tested are measured 

 ready for the test, the acid measure is filled to the 17.5 cubic cen- 

 timeter mark with sulfuric acid, and then carefully poured into 

 a test bottle containing milk. The bottle is held in a slightly 

 inclined position, for reasons given in directions for measuring 

 the sample. The acid being much the heavier sinks directly to 

 the bottom of the test bottle without mixing with the milk 

 that floats upon it. The acid and milk should be thoroughly 

 mixed together by gently shaking with a rotary motion. At 

 5 



