RlRAL Sen (JUL Leai-'let. 



689 



Fig. 26. — Test 

 bottle. 



Lesson XL 



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. 26), one pipette to measure the milk 

 (Fig. 27), one acid measure (Fig. 28), about one pint of 

 sulfuric acid with specific gravity between 1.82 and 1.83. a 

 few ounces of milk, and some hot w^ater. 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 thoroughlv mixed just before the 

 sample is taken, to make sure that the fat 

 or 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 w'ith 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. 29) . 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 wath the pipette. 



It is best always to make this test in dupli- 

 cate ; hence two bottles are needed for each lot of 

 milk. 



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



jf,,i^) handled with great care. If any gets on the hands, face or 



C — !^' clothing, it should be washed ofif quickly and water should 



Fig. 28.— always be ready for this purpose. Do not leave the acid 

 And weas- , , ., , ^ . 



ttyg where young children can r/et if. 



IK 



Fig. 27. — 

 P i p cttc 

 or milk 

 measure. 



