96 Testing Milk and Its Products. 



always be balanced before being used and the weights 

 kept bright and clean. 



Carelessness in weighing may be the cause of very 

 inaccurate results, and the importance of a sensitive 

 scale cannot be over-estimated. Scales with a graduated 

 side beam are preferable to those that require the use 

 of small weights. Scales sensitive to .01 gram are now 

 on the market, which permit of 20 to 50 grams of butter 

 being weighed out for testing.^ 



103. Fat in butter. The Babcock test can be used 

 with a fair degree of accuracy for estimating the per 

 cent, of fat in butter, by weighing 9 grams of butter 

 into a test bottle graduated to measure 50 per cent. fat. 

 About 10 ce. of hot water is added to the butter, and 

 17.5 cc. of sulfuric acid of one-half the strength used in 

 milk testing. Mix the butter and acid until the curd 

 is all dissolved, add hot water to bring the fat into 

 the neck of the test bottle and whirl in a centrifuge. 

 When a clear separation of the fat is obtained the test 

 bottle is placed in water'of 140° F. up to near the top 

 of the neck and after standing a few minutes in this 

 water the fat column is read off ; the reading multiplied 

 by 2 gives the per cent, of fat. 



Accurate results can only be obtained by taking great 

 care in all the manipulations, especially in weighing the 

 butter and in reading the fat at the proper tempera- 

 ture. Small errors in making tests have a marked influ- 

 ence on the results, because the butter fat is such a 

 large per cent, of the butter. Tests should always be 

 made in duplicate.^ 



' See bull. 154, Wisconsin exp. sta., p. 10. 



^ Special bottles for testing butter for Its fat content have been put 



