ESSAY XVII. 



ON MILK AND ITS ACID. 1780. 



SECTION I. 



IT is well known that milk contains butter, cheese, sugar of 

 milk, some extractive matter, and a little salt ; the rest is 

 water. But we are yet far from having a just chemical 

 knowledge of this substance. I shall first consider a little 

 the separation of the cheese from the serum, etc., and after- 

 wards inquire into the acid, and the properties which whey 

 or milk acquires in a warm place. 



SECTION II. 



(a) If any vegetable or mineral acid be mixed with milk, 

 it is well known that the separation of a cheesy matter 

 ensues. This cheese becomes perfect, if the mixture be 

 assisted by the application of heat, since in this case the 

 cheesy particles all coagulate into one mass. Mineral acids 

 yield less cheese than the vegetable. 



(&) If you put into boiling milk as much of any neutral 

 salt as will dissolve in it, the cheesy parts will also separate 

 from the serum or whey. The same thing happens with all 

 earthy and metallic salts, and likewise with sugar and gum- 

 arabic. 



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