196 ESSAY XVII. 



SECTION III. 



Caustic alkalies will dissolve the curds by the aid of a 

 boiling heat; and it may be again precipitated by acids. 

 Hence one may easily be induced to conjecture that the 

 cheesy part is dissolved in the milk by means of an alkali. 

 In order to find out whether this was really the case, I 

 coagulated some milk with a little nitrous acid, filtered and 

 evaporated the whey, but not the least mark of nitre was 

 discovered in it, but only the common sugar of milk. The 

 coagulation of the milk by acids must consequently be 

 owing to some other cause. 



SECTION IV. 



(a) The curds obtained by means of mineral acids always 

 manifest signs of acidity. It is likewise partially soluble in 

 boiling water. 



(b) If with eight parts of water mixed with one part of 

 precipitated, but not dry curds, so much mineral acid be 

 mixed that the water acquires a sourish taste, and it be 

 afterwards boiled, the cheese will be dissolved. Vegetable 

 acids and the acid of milk dissolve little or nothing of the 

 curds. Hence it appears why more curds are obtained by 

 vegetable than by mineral acids (Sec. n. (a)). Hence it is 

 likewise evident why milk coagulates with acids. The curds 

 attract a certain quantity of acid, and this compound requires 

 much more water in order to be kept in solution than the 

 milk contains. 



(c) If milk be mixed with ten parts of water, no curds 

 are obtained by mineral acids. 



(d) If to these acidulous solutions of curds a small 



