. Cyclopedia of farm crops. Farm produce; Agriculture. Fig. 268. The cutting or grinding mectiaiiism of a cider mill. organisms which are abundant in the soil and on the surfaces of the fruits themselves. For certain uses, or when only the acidity char- acteristic of the acetic acid is desired, " vinegar essence," containing high percentages of acetic acid in a relatively pure state, may be made from certain kinds of wood by a process of di-stillation. Undoubtedly much of the cheaper grades of vinegar for table use has its origin in this way. It is cheaper than the production of the
. Cyclopedia of farm crops. Farm produce; Agriculture. Fig. 268. The cutting or grinding mectiaiiism of a cider mill. organisms which are abundant in the soil and on the surfaces of the fruits themselves. For certain uses, or when only the acidity char- acteristic of the acetic acid is desired, " vinegar essence," containing high percentages of acetic acid in a relatively pure state, may be made from certain kinds of wood by a process of di-stillation. Undoubtedly much of the cheaper grades of vinegar for table use has its origin in this way. It is cheaper than the production of the acetic acid by fermenta- tion. By a proper admix- ture of ethers and flavor- giving bodies a solution may be made which simu- lates the product of the fermentation process, but never has the "bouquet" and the fine quality which characterizes the latter kind. Fermentation vinegar. Fermentation vinegar, or that properly used as a condiment, may be prepared from numerous kinds of alcoholic solutions, but especially from cider, wine or beer, through the agency of a class of bacteria generally known as the acetic bacteria. These little organisms have the power, under proper conditions of temperature and aeration, of oxidizing the alcohol to acetic acid and water in accordance with the chemical equation C2H5OH + 02 = + HoO Probably an intermediate substance, aldehyde, is formed sometimes, although it is not certain that this is always the case. In order to have this reaction proceed it is necessary to have (1) a lively and suitable micro- organism ; (2) solutions of relatively weak alcohol, as the organisms are poisoned by amounts much over 10 per cent, and, indeed, will not work rapidly in solutions approaching this concentration ; (3) an abundance of air; and (4) a well-regulated and favorable temperature. The acetic group of bacteria comprises a number of species, perhaps twenty of which have been iso- lated and described, all characterized by their power of oxi
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