During this process the alcohol of the previous vinous fermentation disappears, and its place is occupied by vinegar. Preparation and Description. The Germans have a quick method of making vinegar, by mixing certain proportions of alcohol, water, and honey, extract of malt or ferment, and which, by a certain process is exposed to the atmosphere by distributing it over beech-wood shavings in a large vat, that it may have an extensive surface for oxidation, and is thereby converted into vinegar in from 24 to 36 hours. Vinegar is likewise made by several other processes, some of which require a comparatively short time for its formation. These matters may be removed by boiling the vinegar, and then filtering it.
Good vinegar has a peculiar and grateful odor, and an agreeable sour taste.
The high-colored vinegars may be rendered colorless, by filtration through charcoal, or by distillation in a glass retort. Adulterations and their Detection. Consequently barium chloride, which precipitates the sulphates, is not a good testing reagent to detect free sulphuric acid in vinegar, but upon boiling the latter with calcium chloride a precipitate will show the presence of free acid, but not sulphates, in small amounts. When vinegar is free from sulphuric acid, acetate of lead has no action upon it. Copper may be detected by the addition of ammonia in excess, which renders the vinegar blue, nor should metallic copper be deposited on a clean, bright piece of iron immersed in it.