76 



FARM ARITHMETIC. 



191. Four cans contain milk as follows : 100 pounds, 

 and tests 5,4 per cent ; 80 pounds, 4.3 per cent ; 84 pounds, 

 3.8 per cent ; and 180 pounds, 3.1 per cent. What per cent 

 is the mixture ? 



192. In a can is a certain quantity of milk that tests 

 5 per cent; in another can is a certain quantity that tests 

 3 per cent. The amount of butter fat in both cans is 40 

 pounds, one-fourth of which is in the first can. How 

 much milk is there in each can? 



Babcock Milk Tester. 

 A small tester for four samples. An outfit like this ought to be in every school. 



The Babcock Tester. The Babcock test was discov- 

 ered by Dr. Babcock of Madison. Wisconsin. The test 

 is made as follows : By use of a pipette 17.6 cubic centi- 

 meters of milk are put into a test bottle, then sulphuric 

 acid of the correct strength is measured in a graduate, 

 and 17.5 cubic centimeters of it carefully poured down the 

 side of the test bottle into the milk. The acid and the milk 

 should be thoroughly mixed by being gently shaken with 

 a rotary motion. The mixture becomes hot and has a 

 dark color. The bottles are put in the tester, and the 



