58 DAIRY LABORATORY GUIDE 



by addition of anhydrous alcohol-free ether. Decant 

 the ether and repeat until the fat has all been dis- 

 solved. Allow the residue to dry in the air and 

 weigh. Cover the crucible and heat gently at first, 

 gradually raising the temperature to just below red- 

 ness. The cover may then be removed and the heat 

 continued till the contents of the crucible are white. 

 The loss in weight of the crucible and contents repre- 

 sents casein, and the residue in the crucible mineral 

 matter. In this mineral matter, dissolved in water 

 slightly acidulated with nitric acid, chlorine may be 

 determined gravimetrically with silver nitrate, or 

 volumetrically after dissolving in water only, using 

 potassium chromate as an indicator. From the 

 amount of chlorine, Cl, present the quantity of salt, 

 NaCl, may be calculated or it may be determined 

 as follows: 



DETERMINATION OF SALT 



Weigh in a counterpoised beaker from 5 to 10 

 grams of the butter. The butter is placed, in por- 

 tions of about 1 gram at a time, in the beaker, these 

 portions being taken from different parts of the 

 sample. Hot water is added (about 20 c.c.) to the 

 beaker containing the butter, and after it has melted 

 the liquid is poured into the bulb of a separating 

 funnel. The stopper is inserted and the contents 

 shaken for a few moments. After standing until the 

 fat has all collected on top of the water, the stopcock 

 is opened and the water is allowed to run into an 

 Erlenmeyer flask, care being exercised to let none of 



