86 Testing Milk and Its Products. 



reading difficult. Such defects can usually be over- 

 come by placing the test bottles in hot water for about 

 ten minutes previous to the whirling, or by allowing the 

 fat to crystallize (which is done by cooling the bottles 

 in cold water after the last whirling) and remelting 

 it by placing the bottles in hot water. 



The error due to the expansion of the fat in case of 

 excessively hot turbine testers having no openings in 

 the cover as mentioned on p. 36, is especially noticeable 

 in cream testing, where it may amount to one per cent, 

 or more. In order to obtain correct results with such 

 testers, the hot cream test bottles must be placed in 

 water at about 140 F. for some minutes before the 

 results are read off. 



96. The subject of different methods of reading 

 cream tests has been studied by Webster and Gray/ 

 who conclude that correct results are obtained by 

 taking readings at 120 F., from the bottom to the ex- 

 treme top of the fat column, deducting four-fifths of 

 the depth of the meniscus from this result and adding 

 .2 per cent, to the figure thus obtained. The error due 

 to differences in the diameter of the necks of the test 

 bottles is thus done away with. In the case of tests of 

 9-gram samples, the reading is doubled before .2 per 

 cent, is added. While this method of reading does 

 away with the error "due to the varying depths of the 

 meniscus in bottles with narrow and wide necks, it re- 

 fers to reading the tests at a lower temperature than 

 is now generally practiced in factories, viz., at 120, in- 



1 Bull. 58, Bur. An. Ind., U. S. Dept. of Agriculture. 



