BUTTER. 65 



of boiling water, until the weight is constant. 



Casein and Ash. — The crucible containing the res- 

 idue from the fat determination, consisting of the casein 

 and salts, is covered and heated, gently at first, and 

 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 the weight of the casein, and the residue in the 

 crucible, ash. 



A weighed paper filter may replace the Gooch 

 crucible. 



Antiseptic substances in milk may find their 

 way into the butter made from it. They will be dis- 

 solved in the water, and may be detected by separat- 

 ing this, by melting, and testing it as directed under 

 milk. 



Oleomargarin. — Under this term is now included 

 by act of Congress, any oleaginous substance, intended 

 as a substitute for butter, containing any proportion of 

 fat other than butter-fat. The term " margarine " is 

 employed in England,' under authority of an act of 

 Parliament, with the same significance. The principal 

 materials employed in the preparation of butter-sub- 

 stitutes are cottonseed oil, mutton fat and beef fat. As 

 usually manufactured, they are wholesome and econ- 

 omical. 



Butter fat, like most fats, consists of a mixture of the 

 ethers of tritenyl (Cg H^ ) but is peculiar among animal 



