638 TESTING BUTTER 



and instead of 9 cc. add 12 cc. of lukewarm water just before the 

 acid is added. 



Accuracy of Results. Hepburn, as the result of a comparison 

 of tests between the two 90 per cent butter test bottles and the 

 official, chemical analysis, and embracing work with 124 separate 

 samples of butter, finds the modified Babcock test, as described 

 above, applicable as a successful commercial method for estimating 

 the percentage of fat in butter. 



Other Modifications of the Babcock Test. Earlier attempts 

 to modify the Babcock test, so as to make it suitable for the rapid 

 determination of the fat in butter, resulted in the construction and 

 use of the Wright bottle and the Wagner bottle. In these bottles 

 the graduated portion of the neck has a very narrow diameter and 

 the bulk of the fat is assembled in a bulb which is a part of the 

 graduated neck. 



Tests with these bottles have proven very uncertain and unrelia- 

 ble, probably largely because even slight temperature changes, during 

 the reading of the test, caused very great expansions or contractions 

 of the fat column in the graduated portion of the neck, due to the 

 relatively large volume of fat affected in the bulb of the neck and 

 to the very narrow diameter of the graduated neck. This intensity 

 of expansion and contraction of the thin fat column that is directly 

 connected with the relatively large volume of fat in the bulb of the 

 neck rests on the same principle as the mercury column in the ther- 

 mometer. For these reasons, therefore, the use of these modi- 

 fied Babcock bottles, equipped with bulbs in the neck of the bottle, 

 is prone to yield entirely erroneous results and cannot be recom- 

 mended for the determination of the percentage of fat in butter. 



Gravimetric Determination. 



Indirect Method. Official. Dissolve the dry butter, obtained 

 in the moisture determination 2 in which no absorbent was used, in 

 absolute ether or petroleum ether, transfer to a weighed Gooch, with 

 the aid of a wash bottle filled with the solvent and wash until free 

 from fat. Dry the Gooch and contents at the temperature of boil- 

 ing water until the weight is constant and determine the fat. 



Direct Method. Official. 1 From the dry butter, obtained in 

 the determination of moisture, 2 either with or without the use of an 



1 Journal of the Association of Official Agricultural Chemists, Vol. II, No. 8, 

 November, 1916. 



a See Determination of Moisture in Butter (Official 



