METHODS OF TESTING BUTTER FOR WATER 123 



end downward and the amyl reagent 

 in the bulb agitated in order to rinse 

 down any water adhering to the sides 

 of the bulb. (9) After cooling the 

 tube and contents the percentage of 

 water is read directly from the scale, 

 when a lo-gram sample is used. The 

 water is in the lower part of the tube. 

 The reading is made to the lower part 

 of the meniscus. When any amount 

 of butter other than 10 grams is used, 

 a corresponding correction must be 

 made. 



The accuracy of the results obtained 

 by the Gray method depends upon 

 several factors, chief of which are the 

 following: (i) The graduation must 

 be correct. (2) The amyl reagent 

 must be pure. (3) The manipulation 

 as described must be followed strictly, 

 (a) Too rapid heating must be avoided 

 in order to avoid the danger of driv- 

 ing water-vapor into the air from the 

 upper end of the condensing-tube. (b) 

 The rubber stopper B (Fig. 3/b) must 

 fit the neck of flask A perfectly and 

 must be free from cracks. A loose- 

 fitting stopper may allow loss of water 

 either by escaping into the air or by FIG. 3;b 

 collecting between the neck of the flask GRAY 's APPARATUS 

 and^ the stopper. Repeated heating 

 causes the rubber stoppers to crack IN BUTTER. 



