102 MANUAL OF GENEEAL AGEICULTURI1. 



should be spilled on-^the^skin or clothing, it should be 

 quickly washed off with water. Color can be restored 

 to clothing by treating the spot at once with ammonia 

 water. 



(f) Whirling the Bottles. Place the test bottles with 

 the milk and acid properly mixed in the tester or centri- 

 fugal machine. The bottles should be arranged in pairs 

 at the opposite side of the center, so that they will balance 

 when rotating. It is better to put the bottles into a tester 

 directly after mixing the milk and acid, while the bottles 

 are hot. If, however, this should not be convenient, the 

 bottles may be allowed to stand an indefinite period, but 

 when they are placed in the machine, means should be 

 provided for heating them while rotating so as to keep 

 the fat in a melted condition. This is done in the steam 

 machine by turning on a steam jet provided for that pur- 

 pose or in the hand machine by placing boiling water in 

 the bottom of the tester and putting on the cover at once 

 to retain the steam. The bottles should be whirled for 

 five minutes at the speed marked on the machine, and 

 then the machine allowed to slowly come to rest for the 

 purpose of adding hot water. 



(g) Adding Hot Water. The object of adding hot 

 water is to bring the fat up into the graduated portion 

 of the neck where it can be measured. Boiling hot water 

 should be added by means of the pipette or a beaker. 

 Perfectly clear readings can be insured by adding the 

 water in two installments. First, add enough hot water 

 to bring the fat to, but not into, the neck of the bottle, 

 then whirl for two minutes. Stop, and add enough hot 

 water to bring the fat into the graduated part of the 

 neck, adding the water gradually so as not to overflow 

 the fat. Whirl a third time for one minute. With this 

 method a beautifully clear reading should result with a 

 layer of clear water below the fat. If the reading of the 

 fat is at all cloudy add a little hot water and whirl again. 

 It is desirable to use distilled water, rain water, or soft 

 water of any kind. 



