112 GRADING AND TESTING MILK AND CREAM 



and dry separatory funnel must be weighed, and this as well as the 

 other weighings involved must be done with care. This weight 

 once found will suffice for all determinations made with that par- 

 ticular funnel, unless by accident some of the glass should be 

 chipped off. A slight scratch made with a file can serve to iden- 

 tify the funnels. A paper label should not be used. If requested 

 at the time of ordering we will number them without additional 

 charge. 



" Each time, before using the separatory funnels, 'they should 

 be lubricated with a properly prepared stopcock lubricant which 

 we supply with directions for its use. 



" I. Weighing the Charge. Counterpoise the small beaker 

 on the balance and carefully weigh out 20 grams of the sample 

 mixed as directed. 



" II. Transferring the Charge to the Separatory Funnel. 

 Place the beaker containing the charge on a radiator or steam 

 pipe until the butter is melted. (This may. also be accom- 

 plished by adding a small quantity of boiling water.) Next 

 pour the charge into the funnel kept in an upright position in the 

 wooden rack. No part of the charge must be lost in transferring. 

 With a fine stream of hot water rinse down the sides of the 

 beaker and pour the rinsings into the funnel. (If the salt is to 

 be determined, distilled water must be used. See directions 

 under ' Salt Test.') Repeat this, using not more than a tea- 

 spoonful of water at a time until the funnel is full to within 

 about one-quarter of an inch of the shoulder. The rinsing can 

 be done very conveniently with the arrangement on many steam 

 centrifuges for filling the 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. 



