VINEGAR FERMENT AND ITS CONDITIONS OF LIFE. 31 



ditions will first be briefly enumerated and then the separate 

 points more fully discussed. 



For the vinegar bacteria to settle upon a fluid, and for their 

 vigorous augmentation the following factors are required : 



1. A fluid, which, besides alcohol and water, contains nitro- 



genous bodies and alkaline salts. The quantities of these 

 bodies must, however, not exceed a certain limit. 



2. The fluid must be in immediate contact with oxygen (at- 



mospheric air). 



3. The temperature of the fluid and the air surrounding it 



must be within certain limits. 



As regards the composition of the nourishing fluid itself, it 

 must contain all the bodies required for the nourishment of a 

 plant of a low order. Such substances are carbohydrates, albu- 

 minates, and salts. Alcohol must be named as a specific nourish- 

 ment of the vinegar ferment, provided the supposition that the 

 latter consumes the alcohol and separates in its place acetic acid 

 is correct. The quantity of alcohol in the fluid intended for the 

 fabrication of vinegar must, however, not exceed a certain limit, 

 a content of 15 per cent, appearing to be the maximum at which 

 acetous fermentation can be induced. But even a content of 12 

 to 13 per cent, of alcohol is not very conducive to the vegetation 

 of the vinegar ferment, and every manufacturer knows the diffi- 

 culty of preparing vinegar from such a fluid. Like a high con- 

 tent of alcohol, a large quantity of acetic acid in the nourishing 

 fluid exerts also an injurious influence upon the vinegar ferment. 

 Upon a fluid containing 12 to 13 per cent, of acetic acid, and 1 

 to 2 per cent, of alcohol, the ferment vegetates only in a sluggish 

 manner, and considerable time is required to convert this small 

 quantity of alcohol into acetic acid. 



That the vinegar ferment cannot live in dilute alcohol alone 

 may be shown by a simple experiment. By placing fully developed 

 ferment upon a fluid consisting of only water and alcohol, a very 

 small quantity of acetic acid is formed, but the ferment perishes 

 in a short time it starves to death. A fluid suitable for the 

 nourishment of the ferment must therefore contain the above- 

 mentioned nourishing substances, sugar, dextrine, or similar com- 

 binations occurring in wine, malt extract, beer, being generally 



