642 TESTING BUTTER 



Babcock test bottles, i. e., the rubber tube ending in a glass or metal 

 point and connecting with a water tank heated by steam. The point 

 must be fine, however. Should it be larger than three-sixteenths 

 of an inch it can be replaced with the tip of a small oil can. Should 

 this arrangement not be at hand one can easily be improvised from 

 a tin can, a rubber tube, and an oil-can tip. In transferring the 

 melted butter and rinsings the last drop may be prevented from 

 running down the outside of the beaker, by touching the lip of the 

 beaker to the neck of the separatory funnel. 



III. Centrifuging. "Insert the separatory funnel in the special 

 socket, allowing the stem to project through the hole in the bottom 

 and the handle of the stopcock through the open side. (Caution: 

 The socket must always be placed in the centrifuge with the open 

 side facing the direction in which the wheel revolves. This is very 

 important, for if the opening faces the reverse direction the stop- 

 cock will be thrown out and broken. ) Whirl one minute at the same 

 speed used in testing milk with the Babcock test. The centrifuge 

 must be kept warm. 



IV. Removing the Water. "Remove the separatory funnel 

 from the socket and allow the water to flow through the stopcock 

 until the fat (or curd) is within one-eighth of an inch of the stop- 

 cock. In this and subsequent operations involving the stopcock one 

 must be sure it does not stick. It must always be under control, and 

 it is best to give it frequent slight movements when the water or acid 

 is running through it to be sure that this control is maintained; 

 otherwise it might stick at a critical moment and the determination 

 be lost. The most of the salt and part of the curd are taken out by 

 the water. The remainder of the curd and all of the fat stays in the 

 funnel. 



V. Dissolving the Curd. "Measure out 9 cubic centimeters of 

 cold water, preferably condensed steam, with the glass graduate and 

 pour into the beaker. Add to this 11 cubic centimeters of sulphuric 

 acid of the same strength used in testing milk and cream (specific 

 gravity, 1.82-1.83) and mix by gently shaking. (Caution: Always 

 add acid to water and not water to acid, or a serious accident may 

 result.) While still very hot add the mixture to the contents of the 

 separatory funnel. Now dissolve the curd by giving the funnel a 

 circular motion with the hand grasping the neck. Centrifuge one 

 minute, as before. Draw off the acid solution till the fat layer is 



