932 Rural School Leaflet. 



Lesson XI 



THE BABCOCK TEST FOR BUTTER-FAT IN MILK 



By R. a. Pearson 



Object. — To become familiar with a quick and accurate method of 

 showing the richness of milk, which means its percentage of fat. 



Utensils. — A hand-power centrifugal tester, at least two 

 milk test-bottles (Fig. 48), one pipette to measure the milk 

 (Fig. 49), one acid measure (Fig. 50), about one pint of sul- 

 furic acid with specific gravity between 1.82 and 1.83, a few 

 ounces of milk, and some hot water. All the 

 necessary apparatus and acid can be purchased 

 for about five dollars from any dairy supply com- 

 pany. They can be ordered through a hardware 

 dealer. Sulfuric acid is sold also at drug stores. 

 Sampling the milk.— The milk to be tested 

 should be. thoroughly mixed just before the 

 Fig. 48. — sample is taken, to make sure that the fat 

 Test bottle ^^ cream is evenly distributed. This can best 

 be done by gently pouring back and forth between two vessels 

 several times. The milk should be neither very cold nor hot. 

 Place the small end of the pipette at the center of the milk 

 and suck the milk up above the 17.6 cc mark. Quickly put 

 the index finger over the upper end of the pipette and by 

 releasing the pressure allow the milk to run out until its upper 

 surface is even with 17.6 cc mark when the pipette is held 

 straight up and down. 



Place the point of the pipette a short distance into the 

 test-bottle neck, holding it against the glass and with both 

 pipette and bottle at an angle (Fig. 51). Remove the finger to 

 allow the milk to flow into the bottle. Be sure to get every 

 drop of the milk, taking care to drain the pipette and to blow 



the last drop into the bottle. A little practice ^ 



should make anyone proficient with the pipette. 



It is best always to make this test in dupli- Pipette 



cate; hence two bottles are needed for each lot of ^^ ^^^^ 

 ... measure 



milk. 



Using the acid. — The acid is very strong and must be 

 handled with great care. If any gets on the hands, face or 

 clothing, it should be washed off quickly and water should 



Acid meas- always be ready for this purpose. Do not leave the acid 



ure where young children can get it. 



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