124 MODERN METHODS OF TESTING MILK 



and they are then liable to collect and retain water in 

 the cracks ; this trouble may be remedied to some ex- 

 tent by rubbing the stopper thoroughly with amyl re- 

 agent before use each time, (c) The sample must be 

 heated long enough to remove all water not only from 

 the butter but from the flasks as well. Comparative 

 tests reported by some workers indicate that more 

 accurate results are obtained by heating the butter 

 until black or nearly so. 



One serious objection to the apparatus is that it is 

 easily broken. This objectionable feature has been 

 obviated in the Mitchell- Walker test (Eastern Dairy 

 School, Kingston, Ontario, Can.), which utilizes es- 

 sentially the principle of the Gray test; most of the 

 parts are of metal and the manipulation is compara- 

 tively simple. 



