388 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



it directly with oxygen in a eudiometer. The results are 

 shown below : 



ALCOHOL. ETHER. 



Lavoisier, de Saussure. Calculated. de Saussure. Calculated. 

 Carbon . 28*5 52*0 52*2 68*0 64*9 



Hydrogen 17-4 137 13-0 14-4 13-5 



Oxygen . 54-1 34-3 34*8 17-6 21 '6 



The vapour densities of alcohol and ether were deter- 

 mined by Gay-Lussac in 1815 (Ann. de Chimie, 1815, 95, 



Lavoisier's work on vinous fermentation (1789). 

 More important than the isolated analysis of spirit of wine 

 is Lavoisier's complete investigation of the process of vinous 

 fermentation, as described in his Treatise, in 1789 (Works, 

 I. 100-108) Lavoisier was able to show that 



" The effects of fermentation reduce themselves to a sep- 

 aration of the sugar, which is an oxide, into two portions, 

 oxygenating one portion at the expense of the other to form 

 carbonic acid ; deoxygenating the other in favour of the first 

 to form a combustible substance, which is alcohol ; so that, 

 if it were possible to recombine these substances, alcohol and 

 carbonic acid, sugar would be reproduced " ( Works, I. 107). 



Lavoisier took 100 Ib. of sugar, 400 Ib. of water and 10 

 Ib. of yeast-paste containing about 7 Ib. of water. At the 

 end of some days 35 Ib. of carbonic acid had escaped, 

 carrying with it 14 Ib. of water. There remained 460 Ib. 

 of liquor, containing 409 Ib. of water, 58 Ib. of alcohol, 

 2 Ib. of acetic acid, 4 Ib. of sugar and i Ib. of (dry) yeast. 

 Lavoisier worked out a balance-sheet as follows : 



Before Fermentation : 



Hydrogen. Oxygen. Carbon. Nitrogen. Total. 



Water . 6i.i.3 l 346. 2.4 = 407. 3.7 



Sugar . 8.0.0 64. o o 28. o.o = 100. o.o 



Yeast . 0.4.5 1. 10. 2 0.12.5 0.0.5 = 2.12.1 



69.6.0 411.12.6 28.12.5 0.0.5 = 510. 0.0 



1 8 gros=i ounce, 16 ounces = i pound; the grains have been 

 omitted from the table. 



