200 ESSAY XVII. 



mucilaginous matter. We have only then to separate all 

 these heterogeneous bodies from the acid in order to obtain 

 it as pure as possible. Distillation would indeed be the 

 shortest way, but this will not answer ; for, though some 

 vestiges of an acid appear in the receiver, which acid is a 

 kind of very weak vinegar, and the cause of the sourish 

 smell of the whey, almost all the acid remains in the retort ; 

 and if the heat be increased, this acid will be decomposed ; 

 I therefore make use of the following process : 



SECTION VIII. 



I evaporated sour whey till one-eighth only remained. 

 The cheesy part being then perfectly separated, I strained 

 the acid. In order now to obtain the animal earth, as I 

 knew that this kind of earth is precipitated by lime-water 

 (Sec. VIL), I saw no other way than to saturate the acid with 

 lime. I then filtered the solution, and diluted it with a 

 triple quantity of water. To separate the lime again from 

 its solvent, the acid of sugar was a most excellent medium. 

 I therefore dissolved a quantity in water, and afterwards 

 added this solution to the solution of lime, till no more 

 saccharated lime precipitated, observing carefully not to add 

 more acid of sugar than was requisite, which I could easily 

 discover by means of lime-water. There now remained the 

 other substances to be separated from the acid of milk. For 

 this purpose I evaporated it to the consistence of honey, 

 then dissolved it in highly rectified spirit of wine, and thus 

 separated from it both the sugar of milk and the remaining 

 heterogeneous substances. The acid alone being thus dis- 

 solved in spirit of wine, I filtered it, and then mixed some 

 pure water with this acid solution ; and after separating the 



