106 VINEGAR, CIDER, AND FRUIT-WINES. 



The quantity of alcohol for the first effusion should be so chosen 

 that the fluid running off still contains a small quantity of un- 

 changed alcohol, this being an assurance that only alcohol and 

 not unfinished acetic acid has undergone an alteration. As long 

 as alcohol is present in the alcoholic liquid the vinegar ferment is 

 almost entirely indifferent towards acetic acid, but after the oxi- 

 dation of all the alcohol it attacks the acetic acid and decomposes 

 it to carbonic acid and water. This can be shown by a very 

 simple experiment. If finished vinegar, instead of alcoholic 

 liquid, be poured into a generator in full operation, the vinegar 

 running off shows a smaller percentage of acetic acid than that 

 poured in, the acetic acid wanting having been destroyed by the 

 ferment. 



To what an extent even smaller quantities than 14 to 15 per 

 cent, of alcohol or acetic acid exert a restraining influence upon 

 the augmentation and activity of the vinegar ferment can be seen 

 in generators charged with alcoholic liquid of different strengths : 

 those containing less concentrated liquid can in the same time 

 form a much larger quantity of acetic acid than those ill which a 

 liquid is used which already contains certain quantities of acetic 

 acid. Hence the greater the quantity of acetic acid already con- 

 tained in the alcoholic liquid the slower the conversion of the 

 alcohol still present into acetic acid. 



It may, therefore, be laid down as a rule that the manufacturer 

 should not strive to prepare vinegar with more than about 12 

 per cent, of acetic acid. Though in exceptional cases a product 

 with 13 per cent, can be obtained, it will also be observed that 

 the respective generators gradually yield a weaker product or that 

 their activity suddenly ceases to such an extent as to require them 

 to be placed out of operation.. 



The preparation of high-graded vinegar being undoubtedly 

 subject to greater difficulties than that of a weaker product, 

 the question might be raised whether the manufacture of weak 

 vinegar only would not be the most suitable. This must be 

 largely decided by local conditions. For a manufacturer whose 

 custom lies in the immediate neighborhood, for instance, in a 

 large city, the production of weak vinegar only would be advis- 

 able, but if he has to send his product a considerable distance, 



