DETERMINATION OF CASEIN 57 



Cleaning the A-p-paratus 



Flask. The flask may be cleaned by washing 

 with soap, washing powder, or washing soda in hot 

 water. It is not absolutely necessary to wash the 

 flask after each determination; the residue may be 

 poured out and the flask wiped with a cloth or thin 

 paper. The flask must always be dry (free from 

 water) before making a determination. 



Graduated Tube. After making the test, empty 

 the tube C by holding the stoppered end downward, 

 removing the stopper and aUowing the contents to 

 flow out quickly. In this way the amyl reagent 

 runs out after the water and carries with it practically 

 all of the water, which might otherwise adhere to 

 the tube. The tube, after emptying, should be swung 

 in the manner described for separating water from 

 amyl reagent, which will almost completely empty it. 

 Following this plan it is not necessary to dry the 

 tube after each determination. Occasionally the 

 tubes should be washed carefully with a hot solution 

 of sodium carbonate (sal soda) or other good washing 

 powder and thoroughly dried before using. 



EXERCISE XIV 



Determination of Casein, Ash, and Salt of 

 Butter 



Carefully weigh a dry porcelain dish or crucible and 

 place thereon a sample of butter. Weigh and sub- 

 tract weight of dish. Dissolve ether extract (fat) 



