202 ESSAY XVII. 



(10) Lead was dissolved after some days' digestion; the 

 solution had a sweet astringent taste, and would not crystallise. 

 I observed afterwards a small quantity of a white sediment 

 in this solution, and found it to be vitriol of lead. Thus 

 there is likewise some vestige of vitriolic acid in milk. 



SECTION X. 



From these experiments it appears that the acid of milk 

 is an acid of a peculiar kind ; and though it expels the 

 vinegar from the acetated vegetable alkali, yet it seems 

 destined, if I may so speak, to be vinegar ; but from the 

 want of such substances as, during fermentation, produce 

 some spirituous matter, it seems not to be volatilised, though 

 a portion of it indeed arrives at this point, and really becomes 

 vinegar ; for without a previous spirituous fermentation, or 

 without brandy, there never arises any vinegar. But that 

 the milk enters into a complete fermentation, though there is 

 no sign of brandy present, appears from the following experi- 

 ment : If a bottle full of fresh milk be inverted into a vessel 

 containing so much milk that the mouth of the bottle reaches 

 below the surface, and if you expose this bottle to a degree of 

 heat a little greater than our summer heat, you will find, in the 

 space of twenty-four hours, that the milk is not only coagulated, 

 but likewise diminished in the bottle, and that in a couple of 

 days afterwards the aerial acid extricated from the milk 

 will have expelled the greater part of it out of the bottle. 

 I said above that the acid of milk cannot be converted into 

 vinegar, from the want of such substances as, during 

 fermentation, produce brandy. This appears to be evident 

 from this : If to a can of milk you add five spoonfuls 

 of good brandy, and expose the vessel, well corked, to heat, 



