MILK. 225 



& Co., Little Falls, N. Y., are, in the author's opinion, the 

 best hand-machines on the maiket at the present time. 

 Steam turbine machines are to be recommended for factory 

 use; they should always be provided with a speed indicator 

 so as to avoid too slow or too rapid whirling: several acci- 

 dents have happened where the bottles were unable to 

 stand the pressure caused by too rapid whirling. 



In Sharpies' Russian Babcock Tester (a steam turbine 

 test r.anufactured by Elgin Mfg. Co., Elgin, 111.) the bot- 

 tles used can be filled with hot water while the machine is 

 in motion ; the test bottles used are arranged for half the 

 usual quantity of milk. 



Points to be watched in making tests by the Babcock 

 method : 



The strength of the acid used is very important; its 

 specific gravity should not go below 1.82 or above 1.84 ; if 

 the acid is somewhat too strong less may be taken, and a 

 little more if it is rather weak. It is, however, not possible 

 to make a satisfactory test with acid of a specific gravity 

 below 1.82. Keep the acid bottle corked when not in use, 

 as the acid will otherwise take up moisture from the air. 



In testing separator skim-milk use a somewhat larger 

 quantity of acid than usual, and whirl 5 to 6 minutes; this 

 will insure a nearly perfect separation of all the fat present 

 in such milks. The two-necked so-called Ohlsscn bottles 

 are recommended for testing separator skim-milk ; the 

 results should be increased by .05 per cent with these as 

 with other test bottles, in testing separator skim-milk. 



The centrifugal machine should run at a rate of about 

 800 to 1000 revolutions per minute; if its diameter is small, 

 whirl 1000 or 1200. 



Soft or rain-water is used in filling up the bottle after 

 boiling, or hard water may be used if some drops of sulfuric 

 acid have been added to it before the boiling. 



In adding the acid the bottle should be held at an angle, 

 so as to cause the acid to follow the inside of the wall. Mix 

 the milk and acid at once, or within a short time, and pro- 

 ceed with the test without delay. 



Read off results before the fat begins to crystallize. If 



