626 TESTING FOR BUTTERFAT 



Experienced testers are able to secure correct readings without 

 glymol by reading to the bottom of the upper meniscus, but the use 

 of glymol is urged for maximum accuracy. 



Glymol should be used in the reading of the cream test only; 

 the milk test should be read without glymol, otherwise the results 

 of the milk tests would be too low. Experimental results by Hun- 

 ziker 1 have indicated that in the milk test the meniscus compensates 

 for the loss of residual fat. It therefore must be included in the 

 reading. In the cream test the proportion of residual fat lost is 

 very small and is amply compensated for by the usual impurities in 

 the fat column. 



Coloring Glymol. Some operators prefer the use of colored 

 glymol, though equally satisfactory results are obtained with the un- 

 colored glymol. Glymol is best colored with an aniline dye. A dye 

 that is sold under the trade name "oil red" proves highly satisfactory 

 for this purpose. Add 1 gram of oil red to 4 gallons glymol. 



Abnormal Appearance of Fat Column. When the cream test 

 has been properly performed the fat column in the neck of the bottle 

 is clear, translucent and free from milky, curdy and charred matter 

 in or below the fat. Any tests in which the fat column is not free 

 from visible impurities, or in which the fat column rests on a layer 

 of non-fatty material, or of which the reading is otherwise indistinct 

 or uncertain, should be rejected. See also abnormal appearance of 

 fat column of milk tests. 



Testing Skim Milk, Buttermilk and Whey for Butterfat 



Test Bottles. For the Babcock test of skim milk, buttermilk 

 and whey use bottles with double necks, which are especially con- 

 structed for this purpose. The graduation of these bottles varies 

 somewhat with the make of bottle. In some bottles the total gradua- 

 tion is .25 per cent and the subdivisions represent .01 per cent. In 

 others the total graduation is .5 per cent and the subdivisions repre- 

 sent .05 per cent. 



Making the Test. Measure the properly mixed skim milk into 

 the test bottles with the 17.6 cc. pipette used for milk testing. Add 

 20 cc. of sulphuric acid. For best results add the acid in several 

 installments and shake until all the lumps of curd have completely 

 disappeared. Whirl in tester for 10 minutes. 



1 Hunziker, Indiana Agricultural Experiment Station Annual Report, 1914. 



