Chap, 6.] Vinous Fermentation. 63 



detached, and the atom finks by its own weight* 

 The nature of the air which is difengaged was not 

 imderftood till the modern experiments on aeriform 

 fluids afforded fo much afiiftance to chemical fcience* 

 It is now afcertained to be the carbonic acid gas, or 

 fixed air, which, being heavier than atmofpheric air, 

 forms a ftratum in the upper part of the veffel in 

 which the fluid is fermenting, where it may be per^ 

 ceived from its greater denfity. This air, contained 

 in the fermenting vats of brewhoufes, frequently pro- 

 duces the moil fatal effects on the workmen j and a 

 candle dipped into it is as certainly extinguished as if 

 plunged into water. During the time that the fer- 

 mentation is going on, the bulk of the liquid is 

 augmented, Another phenomenon is the production 

 of a gentle heat, equal to about feventy-two degrees 

 of Fahrenheit's -thermometer. After fome days, the 

 number of which varies according to the dilution 

 of the fubftance and the degree of heat, the motion 

 in the fluid diminifhes, the warmth abates, and the 

 cmiffion of air is leffened j the liquor becomes clear, 

 and the fcum, which confifts of the more folid par- 

 ticles and air, becomes heavier in proportion as the 

 air efcapes, and at laft finks. The liquor has now 

 undergone a great change ; it has acquired a pungent 

 and pleafant tafte and fmell, and an inebriating quality, 

 and has loft its fweetnefs. If the liquor is now dif- 

 tilled, inftead of an infipid matter, we obtain an ar- - 

 dent fpirit, and a four, grofs fluid remains behind *. 



By 



The phenomena of fermentation have long been known ; but 

 it remained for Lavoifier to afcertain with accuracy what happens 

 in that procefs. I fhall therefore extract his experiments and con- 

 clufions, as Hated by hirofelf, ia his Elements of Chemiftry. 



T A E L. E 



