8 A DAIRY LABORATORY GUIDE 



also coming into common use. These bottles give 

 the reading direct without any computation. In 

 testing 9 grams one would naturally use one-half 

 the usual amount of sulphuric acid. On account, 

 however, of the large proportion of fat present, the 

 acid is liable to char the fat ; and for this reason it 

 is better to add approximately 9 grams of water 

 and then add a little less than the usual amount of 

 acid. 



The fat column in the neck of a cream bottle is so 

 large that its volume is affected by temperature. It 

 is necessary to read the bottles at some constant tem- 

 perature and the most accurate readings are ob- 

 tained at temperatures from 130° F. to 140° F. In 

 order to obtain the proper temperature the bottle 

 should be allowed to stand for at least three minutes 

 in a water bath, care being taken to have the water 

 in the bath as high as the fat column in the bottle 

 neck. 



The meniscus on the fat column of a cream bottle 

 is large and is not constant so that no rule for in- 

 cluding it in the reading can be formulated. The 

 practice is, therefore, followed of removing the 

 meniscus by adding a few drops of glymol (white 

 mineral oil) to the top of the fat column after the 

 test is completed. This flattens the top of the fat 

 column and gives the best results of any method 

 yet devised. The glymol is easier to use if colored 

 pink with alkana root. 



Butter is tested in the cream bottles, from 3 to 4 

 grams being used for the test. Enough warm 

 water is added to bring the sample up to approx- 

 imately 18 grams, and from 10 to 12 cc. of the sul- 

 phuric acid are used. 



Cheese is also tested in the cream bottle, 4 to 5 

 grams being used. The cheese must first be minced 



