456 MICROBIOLOGY OF SPECIAL INDUSTRIES. 



the batteries runs directly to filters, thence to a pasteurizer, and finally 

 to the storage casks. 



The output of these batteries is from two to five times as great per 

 square meter of acetifying surface as that of the old method; the cost 

 of the operation is considerably less, the loss by evaporation much 

 reduced and the quality equal and much more under control of the 

 manufacturer. 



GERMAN METHOD. In all the methods described, the surface of the 

 liquid exposed to air, where alone acetification occurs, is small compared 

 to the volume of the liquid. In order to hasten and therefore cheapen 

 the process, various devices for increasing the surface in contact with 

 air have been devised. The simplest of these is one sometimes employed 

 in wine-making countries. The pressed pomace of red wine is broken 

 up and placed loosely but uniformly in a tall narrow vat. In a few days, 

 acetic fermentation commences in all parts of the mass. Wine is then 

 sprinkled periodically on top and trickling down over the pomace, it is 

 changed to vinegar by the bacterial film which encases every particle of 

 the mass. The "quick" or German method of vinegar-making is based 

 on this principle. 



The apparatus used in this method consists of a tall cylindrical or 

 slightly conical wooden vat provided with a perforated false head a few 

 inches from the bottom and another, similar in structure, at the same 

 distance from the top. The space between these two false heads is filled 

 with long thin chips or shavings of beech wood which have been 

 thoroughly extracted, first with water and then with good strong 

 vinegar (Fig. 90). 



In operation, the liquid to be acetified is distributed over the top 

 false head intermittently in small amounts. This intermittent supply 

 is accomplished by various automatic devices. If the supply is continuous, 

 the liquid tends to run in streams or currents in certain parts of the vat 

 and much of the acetifying surface is lost; if too rapid, the bacterial film 

 is removed from the upper part of the mass of beech chips and only the 

 lower part is effective. 



From the false head, the liquid passes through numerous small holes 

 to the mass of beech chips, over which it trickles slowly and is acetified 

 by means'of the bacterial film which covers them. By the time it reaches 

 the lower false head, the alcohol is in greater or less amount converted into 

 acetic acid. Usually the liquid must pass through from two to five 



