7i6 THE POPULAR SCIENCE MONTHLY. 



cannot live without the aid of the oxygen of the air. Furthermore, 

 they fix this oxygen upon the alcohol contained in the wine according 

 to the following equation : 46 parts, by weight, of alcohol unite with 

 32 parts of oxygen to form 60 parts of acetic acid and 18 parts of wa- 

 ter. The combustion which results from the taking ujj of these 32 

 parts of oxygen is such that the whole surface of the liquid to a certain 

 3epth shows a temperature several degrees higher than that of the 

 deeper portions ; clouds of vapor rise above the cask, clouds formed 

 mainly of steam, mingled with a few odorous products and some vapor 

 of acetic acid. Little by little all these external phenomena diminish 

 and finally cease entirely, and the mycodermic pellicle falls inert to 

 join the preceding ferment at the bottom of the reservoir. And now 

 instead of a reservoir of wine we have a reservoir of vinegar, in which 

 our learned colleague may again see, at his leisure, and still sentimen- 

 tally, a result of divine foresight, in the form of a final cause. 



But let us continue. Our task that is, the determination of the re- 

 turn of the organic matter to the atmosphere and to the soil has been 

 very little furthered by the second phase of the phenomena which we 

 have just described; the alcohol, 100 parts of which contain more than 

 52 parts of carbon, more than 13 parts of hydrogen, and nearly 35 

 parts of oxygen, all coming from the original sugar, has indeed disap- 

 peai-ed and given place to the acetic acid, but the matter has not be- 

 come gaseous, it has not returned to the atmosphere as it partly did at 

 the beginning. All the carbon of the alcohol has remained in the 

 newly-formed acetic acid. 



Notice what now takes place in our immense reservoir of vinegar, 

 at the bottom of which lie heaped together the stems, the pellicle, the 

 pits, the cells, the parenchyma of the fruit, and our two ferments, the 

 wine-yeast and the vinegar-yeast. The quiet of wliich I spoke, and 

 which was established a moment ago, has not lasted long : the ferment 

 of the vinegar (and the fact is very curious) which has just fallen to 

 the bottom of the cask, exhausted by the immense chemical work 

 which it has produced, rendei'ed inert by the sharp combustion of 

 which it has been the seat, reappears, little by little, on the surface of 

 our acid liquid, always in the form of a very thin pellicle; and, little 

 by little, again the upper strata of the vinegar heat, and again clouds 

 rise above the liquid. These clouds are no longer composed solely of 

 the vapor of water; the latter is still very abundant in them, but it is 

 mingled with torrents of carbonic-acid gas, and this remarkable phe- 

 nomenon continues as long as any acetic acid remains in the liquid ; 

 in other words, after the vinegar ferment, an aerobic ferment one 

 needing air has burned the alcohol and turned it into water and 

 acetic acid, it burns the latter and turns it into water and cai'bonic 

 acid. It also bui'us the original acids of the grape. 



This time, that is, in the third phase of the phenomena, the return 

 to the atmosphere has gone on raj^idly: all the carbon, all the hydro- 



