Useful Rules and Tests 359 



iron; the surface of the curd, melted by the heat, sticks to the iron, 

 and the remainder is carefully and gently pulled away. If the curd is 

 very immature, the melted part readily separates from that not affected 

 by the heat, but when more mature, numerous fine threads of casein 

 are drawn out when the two parts are separated, the length of these 

 threads depending upon the maturity of the curd, and commonly meas- 

 ured in terms of acid, thus, J-inch acid, 2-inch acid, etc. 



To CALIBRATE OR TEST THE ACCURACY OF GRADUATION OF 

 GLASSWARE USED IN THE BABCOCK TEST 



Observe that the graduations are at equal distances apart. Fill 

 the bottle carefully to the point with clean rain water, wipe out the 

 neck carefully, and add from a pipette or burette 2 c. c. water. It should 

 fill the bottle exactly to the 10 point. Or, weigh the bottle filled with 

 clean rain water to the point with delicate balances, fill to the 10 

 point and- weigh again. The difference in weight should be 2 grams. 

 Or, into a dry, empty bottle put 2 c. c. or 27.18 grams mercury, insert 

 a tight-fitting plug carefully to the 10 point, and invert the bottle; the 

 mercury should just reach to the point. The pipette should hold 17.6 

 grams of water, or 239 grams of mercury. Any piece showing a dis- 

 crepancy of 2 per cent should be discarded. 



To TEST BUTTER OR CHEESE WITH THE BABCOCK TEST 



Weigh out on a balance sensitive to .1 gram, from 4 to 8 grams of 

 the substance to be tested. Divide into small pieces and put into an 

 ordinary test bottle, or bottle with detachable neck, with about 10 

 c. c. of warm water. Add the acid, and complete the test in the ordinary 

 way. The percentage of fat will be found by the following proportion: 

 Weight of sample: 18 :: observed reading : per cent of fat; or 

 18 X observed reading 



TTT ~, ', = per cent of fat; 



weight of sample 



e. g.: 4.8 grams of cheese tested, showed a reading of 9.2 per cent 

 fat in the test bottle. The cheese contained: 



18 X 9.2 



- : = 34.5 per cent fat. 



4.o 



THE CORNELL BUTTER MOISTURE-TEST 



The apparatus used in the Cornell moisture-test is an alcohol lamp, 

 stand, asbestos sheet, hot-pan lifter, aluminum cup for holding the 



