II 



BUTTER 



portion (the capillary tube) is cut off about 5 cm. below the 

 point where the tube was drawn out. A couple of drops of 

 clear filtered butter fat are now put into the wider point of the 

 tube, and by manipulation are made to assume the position 

 shown in Fig. 58 a. After the butter has become quite solid, 

 which is done by placing the tube on ice for a couple of hours, 

 the latter is attached by means of a thin rubber band to the 

 thermometer ; the drop of fat being placed on a level with the 

 bulb. The thermometer and the tube are now fastened to a 

 retort stand and sunk in a small beaker 

 of water, which is heated slowly over a 

 small flame, the water being stirred con- 

 stantly. 



When the fat begins to appear translucent 

 the temperature is noted. This is the be- 

 ginning of the melting, and the drop of 

 fat then commences to run and take up the 

 position shown in Fig. 58 b. When the fat 

 is quite transparent the temperature is 

 noted, and this point is known as the end 

 of the melting. 



The melting point of pure butter fat, 

 which has no definite relation to the 

 Reichert-Meissl Value, Hehner's Value, or 

 Hiibl's Iodine Number (see below), varies 

 between 28 and 34'7 C. 



FIG. 58. Melting 

 Point Tube. 



(b) The Point of Solidification. 



To determine this a test-tube is filled to 

 the height of 3 or 4 cm. with clear melted 

 filtered butter fat, and a thermometer sunk into the fat 

 so that the bulb is entirely below the surface. The test- 

 tube is then attached to a retort stand and sunk in a beaker 

 of water having a temperature of 40-50 C., and the 

 water allowed to cool gradually. At first the temperature 

 sinks regularly, and after a time becomes constant. After it 

 has remained constant for a while the mercury begins to fall 

 rapidly. The temperature shown by the thermometer whilst 

 the column of mercury is at rest is the point of solidification. 

 As long as the solidification of the fat is taking place the 



