Wine vinegar made according to this process obtains its peculiar bouquet from the wine em ployed and contains besides all the substances of the wine either unchanged or only partly transformed, some new ones, as acetic ether and other compound ethers. In a similar man ner malt and fruit vinegar may be made. The former contains the extractive substances of the malt, as, for example, dextrin, nitrogenous bodies, phosphates, etc., and the latter contains also malic acid. A very pure vinegar which oantains only a little acetic ether is made from a. =Wine of dilute spirits, some vinegar and a malt-infusion.
Schuetzenbach, perceiving that if the rela tiye surfaces of contact of the alcoholic liquid with air be greatly enlarged the formation of vinegar would be accelerated, in 1823 invented what is termed the anew° or °quick process.° Almost at the same time in England Ham, and Wagrnan in Germany, brought out similar prop ositions. By spreading the liquid over as much space as possible and allowing it to percolate slowly through and diffuse over,. a mass of shavings, mostly of beechwood (or similar material), a thin layer, presenting a large sur face, is formed, one gallon being spread out over 100 square yards. This arrangement favors the chemical appropriation of the oxygen in the current of air caused to pass through the shavings, which not only serves to divide the hquid but also to carry the vinegar ierment, dins hastening acetification. The shavings are first usoured° by soaking in strong vinegar for 24 hours. Cleansed charcoal in pieces the size of a walnut is better even than shavings.
In this process the generator, which is technically termed a 'xgraduator,° consists of a large vessel divided into three superimposed compartments of which the uppermost serves to divide the alcoholic liquid into many fine drops; in the middle compartment, which is die largest, acetification takes place, and the lower one is a reservoir for the vinegar formed. This appa ratus is built in various forms but the most practical is that of a truncated cone, as the alcoholic liquid in its descent can spread over a constantly increasing area, and continually comes in contact with fresh air, entering from below. Fir or other durable wood, except oalc, which contains too many extractive substances, is used. All metallic parts (hoops, etc.) must be well varnished, as heavy rusting will other wise be caused by die vapors of the acetic acid. Various sizes have been tried, but a generator which is about 10 feet high, and three and four feet in upper and lower diameter respectively, has been found the best. A well-fitting cover in which holes are bored closes the top. The current of air is regulated by opening or dos ing some of these holes, as may be necessary. The alcoholic liquid is generally introduced through a rotary sprayer. A thermometer is of course a necessary adjunct The liquid used in this process is usually a mixture containing four and one-half gallons of 42 per cent brandy, nine gallons of old vinegar and 27 gallons of water containing some bran and crushed rye.
Dr. Bersch of Vienna recently invented the automatic plate generator which is so arranged that a formation of aldehyde and the destruc tion of acetic acid already formed is impossible and that the evaporation of alcohol is almost wholly eliminated. By means of thin plates of
beechwood he is enabled to have the alcoholic liquid and the air in undisturbed continual con tact, so that vinegar is formed all the time. His geaerator has the shape of a prism eight feet high, having a base three feet square; the interior is fitted with 10 layers of very thin beechwood arranged in' such a way that the liquid can descend on both sides of the plates, while the air ascends between them undisturbed. Once acetification is induced it can be main tained for years, providing of course the influx of the alcoholic liquid and the. admission of air are properly regulated.
Theoretically 100 grams of alcohol will pro duce 130 grams of acetic acid and will require 300 grams of oxygen to oxidize the alcohol, but in actual practice the yield is less, the losses being in general due to evaporation of alcohol, caused either by imperfect apparatus, or by too rapid oxidation. In general such losses aver age 15 to 20 per cent, although they sometimes amount to 30 per cent. While it is true that rapid oxidation will produce vinegar quickly, yet it is also true that in such rapid oxidation too much of the alcohol evaporates and is not oxidized, so that what is gained in time is lost in matenal, which is the more expensive of the two. The fact that air which has passed a gen erator still contains three-fourths of its oxygen shows that four times the calculated amount of air is necessary in order to fully convert the alcohol into acetic acid. Inasmuch as the forma tion of vinegar is a process of combustion, it is self-evident that heat is developed. 'This fact must always be borne in mind by the vinegar manufacturer, because the vitality of the vine gar ferment depends upon the temperatures to which it is exposed. Its activity is greatest be tween 68 and 95" F. (20 to 35° C); if this limit is passed the formation of vinegar decreases rapidly, while at 104° F. (40° C.) it ceases al together, and 122° F. (50° C.) the 'ferment penshes. Lower temperatures do not affect the ferment as much as higher temperatares do, but , a change from one to the other is not beneficial for the development of the ferment Wood vinegar made by the distillation of wood is used to a large extent for the manufac ture of various acetates, esters, etc., and in dilu tion is sometimes used as vinegar for household and preserving purposes, which practice is, how ever, not advisable, as such vinegar is injurious to health on account of the numerous Secondary ingredients contained in the pyroligneous add (q.v.). The use of such vinegar in food is forbidden by law in some States.
In the household certain precautionary measures are to be followed in the use of vine gar. Vinegar or foods prepared in vinegar, should never t'ie allowed to stand long in copper, brass or tin vessels; even the enamel of ircfn and the glazing on earthenware vessels sometimes contain lead, which forms lead acetate in con nection with the vinegar. Glass or porcelain vessels are best adapted for this purpose.