FABRICATION OF WINE- VINEGAR. 191 



previously mentioned, is an indication of the fluid now containing 

 a comparatively large amount of acetic acid and of the slow oxi- 

 dation of the remaining alcohol. In order to maintain the most 

 favorable conditions for the efficacy of the vinegar ferment and 

 to smoothly and rapidly complete the process the workroom is 

 now so heated as to show a constant temperature of 86 F. as long 

 as the fluid remains in the vats. 



Side by side with the observation of the statements of the 

 thermometer a chemical examination of the fluid has to be carried 

 on, this examination gaining in importance the further the forma- 

 tion of vinegar progresses. If the content of alcohol in the wine to 

 be worked is known, the test is up to a certain stage limited to the 

 determination of the acetic acid, but if the process has so far 

 advanced that to judge from the content of the fluid it contains 

 scarcely 1 per cent, of alcohol, the latter has also to be determined 

 by means of the ebullioscope. From this moment on the course 

 of the process must be very carefully controlled and interrupted 

 when still 0.15 or at the utmost 0.2 per cent, of alcohol is present ; 

 this small amount of unchanged alcohol exerts a favorable effect 

 upon the quality of the vinegar, acetic ether being formed from it 

 and a corresponding quantity of acetic acid during the time the 

 vinegar has to be stored. 



The interruption of the process is best effected by separating 

 the fluid from the layer of ferment floating upon it. The stop- 

 cock H, Fig. 42, is opened and left open as long as fluid runs out. 

 A layer of vinegar about f to 1 inch deep upon which floats the 

 vinegar ferment, remains in the vat, and the stop-cock being closed 

 a fresh supply of alcoholic liquid is introduced through the funnel 

 R until it begins to run out through g. The process then com- 

 mences anew in the manner above described. 



Theoretically unlimited quantities of wine could be converted 

 into vinegar by means of such an apparatus, as the vinegar fer- 

 ment which floats upon the fluid remaining in the vat, rapidly 

 augments upon the fresh supply of wine and converts it into 

 vinegar. In practice an occasional short interruption of the pro- 

 cess is, however, necessary. During the conversion of the wine 

 the greater portion of albuminous substances held in solution in 

 it separates as flakes, and, further, a portion of the vinegar ferment 



