the water made use of, is rain water that has flowed from shingle roofs, and is of a dirty, yellowish color. Usually, this color disappears after being passed through the generator the second or third time, but when this fails to remove the color, it is usual to cover the false bottom of the generator to the depth of five inches, with rice, and then packing on this the usual quantities of sand, as before described. The liquid that has been filtered through rice, is beautifully transparent, but when the rice filtration is not practicable or cannot be made available without difficulty, this objectionable color in the vinegar will have to be concealed by coloring it with burned sugar, same as for cider vinegar. The novice will recollect to add the coloring in minute quantities, otherwise the vinegar might become too highly colored.
What has been said about adulterating vinegar, only applies to the cheap vinegar. Pure vinegar can be manufactured by the use of the generators, at such an astonishing low price, that adulteration would appear useless.
Colored and flavored vinegars have but recently r appeared in commerce. They are usually made of sulphuric acid diluted with water, and colored to suit the fancy. The aromatizing articles consist of the oils of wintcrgreen, lemon, orange, almonds, vanilla, ambergris, cil of rose»; &c., &c. Perfumed vinegars are generally colored, and are usually found in five to ten gallon kegs.
Adulterations of Vinegar.—The principal foreign substances which vinegar is liable to contain are sulphuric and sulphurous acids, certain acrid substance* copper and lead derived from improper ves-seli^used in its manufacture ; muriatic and nitric acids are but rarely present. Chloride of calcium Will detect free sulphuric acid when boiled with the vinegar, without causing the least precipitate with the minute quantity of sulphates always present in the liquid. Chloride of barium is not a suitable test here, as it will cause a precipitate with these sulphates, when no free sulphuric acid is present. Sulphurous acids may be detected and estimated by first precipitating the sulphates and free sulphuric acid, by baryta water, next acting 011 the vinegar with arsenic acid, wiiich converts sulphurous acid into sulphuric acid ; and, finally, precipitating the newly-formed sulphuric acid by chloride of barium from the sulphuric acid in the last precipitate. Its equivalent of sulphurous acid is easily calculated. Muriatic acid may be discovered by adding to a distilled portion of the suspected vinegar a solution of nitrate of silver which will throw down a curdy white precipitate, if nitric acid be present—an improbable impurity. It may be detected by its producing a yellow color when boiled with indigo. The acrid substances usually introduced into vinegar are red pepper, long pepper, Guinea pepper, pelli-tory, and mustard. These may be detected by evaporating the vinegar to an extract, which will have an acrid, biting taste, if any one of these substances should be present.
By far the most dangerous impurities in vinegar are copper and lead. The former may be detected b}r a brownish precipitate on the addition of ferro-cvanuret of potassium to the concentrated vinegar. The latter by a blackish precipitate with sulp'nuret-ed barium, and a yellow one with iodide of potassium.
P|re vinegar is not discolored by sulphureted hydrogen.
The essential ingredients of pure vinegar arc acetic acid and water ; but, besides these, it contains various other substances derived from the particular vinous liquor from which it may have been prepared. Among these may be mentioned coloring matter, gum, starch, gluten, sugar, a small portion of alcohol, and frequently malic and tartaric acids, with a minute proportion of alkaline and earthy salts.
Che method pursued in making Wine Vinegar in b mce, where it is manufactured iu the greatest pt fection, is as follows! Casks are employed of about the capacity of eighty-eight wine gallons ; those being preferred which have been used fcr a similar purpose. They are placed upright in three rows, one above the other ; each cask having an opening at the top of about two inches in diameter. Iu summer, no artificial heat is required ; but the wine intended to be converted into vinegar is kept in separate casks containing beech shavings, on which the lees are deposited. Twenty-two gallons of good vinegar, boiling hot, are first- introduced into each vinegar cask, and at the end of eight days about two galloas of the wine, drawn off clear, are added ; and the same quantity is added every eight days until the casks are full. After this the vinegar takes about fifteen days to form. At the end of that time only half tho contents of each cask is drawn off; and it is filled .ip again by the addition of two gallons of wine every eight days as at first. In some cases, however, the quantity of wine added, and the intervals between the successive additions, are greater or less than those here indicated. The variations in this respect depending upon the progress of the fermentation to deiarmine this point, the operator plunges a stave into the cask, aad upon withdrawing if they find it covered with froth, they judge that the fermentation is going on properly, and accordingly add more wine.
When the infusion of malt is employed in the manufacture of vinegar, the process is as follows: The infusion of malt, when properly cooled, is put into large fermenting tuns, and by the addition of yeast the liquid is fermented for four or five clays. It is then distributed into smaller vessels, and placed in a room heated by means of a stove, and kept, there for about forty days, or until the mass has soured. It is then transferred to common barrels, which are placed in the open air, the bung-holes being covered with a tile to keep out the rain. In this situation they are allowed to remain for several months, or until vinegar is formed.
The process is then completed in the following manner : Large tuns are prepared with false bottoms, on which is put a quantity of the refuse of raisins and other fruits, technically called rape. These tuns are worked in pairs, one being filled with the vinegar from the barrels, and the other tun only three fourths filled. In the latter, the fermentation takes place more rapidly, and the process is'rendered more active, alternately, in one or the other tun, by filling up each daily from the other until the process is completed.
Vinegar is often made from cider. The cider is placed in barrels with their bung-holes open. These barrels are exposed during the summer to the heat of the sun. The acetification is completed in the course of about two years. The progress of the fermentation must be watched, and as soon as perfectly formed it should be drawn off into clean barrels.
Without this precaution the acetous fermentation would pass into the putrefactive, and the whole of t^e vinegar would be spoiled.
Malt Vinegar has a yellowish-red color. Tno strongest kind, called "Proof Vinegar," contains from four to five per cent, of acetic acid : that of British manufacture usually containa.;sulphuric acid. The law allows the addition of the one thousandth part of this acid.
Wine Vinegar is nearly one sixth stronger than pure malt vinegar. It is of two sorts, the white and the red, according as it is prepared from white or red wine.
to distinguish WniTE WLNE from malt vineg1r.
¿.dd one ounce of water of ammonia to the surne quantity of the vinegar, which, if it is white wine, will produce a purplish inuddiness, and a purplish precipitate ; and malt vinegar produces eitnor no effect, or a dirty brownish precipitate.
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