on the surface of a fresh liquid and kept at a proper temperature the development of the ferment again begins and continues with great rapidity.

Duclaux says: "These little beings reproduce themselves with such rapidity that by placing an inperceptible germ upon the surface of a liquid contained in a vat having a surface of one square meter (about one square yard), we may see it covered in from twenty-four to forty-eight hours. with a uniform velvety veil. If we suppose that there are three thousand cells in a square millimeter, this will give us for the vat three hundred millions of cells produced in a very short time."

As the result of many experiments, the conditions most favorable for the production of the vinegar ferment and the conversion of the largest quantity of alcohol into acetic acid are well known. These are:

1. A fluid which, besides alcohol and water, contains nitrogenous bodies and alkaline salts.

The quantities of

these must, however, not exceed a certain limit.

2. The fluid must be in immediate contact with the air. 3. The temperature of the fluid and the air surrounding it must be within certain limits (68°-95° F.) The substances used for the manufacture of vinegar are quite numerous. All wines and fruit juices, molasses, beer, solution of glucose, and in fact any fluid containing fermentable sugars. The methods employed in the various processes of manufacturing vinegar belong to one of two classes, the old process of self fermentation, and the new or quick process.

Depending on the material used, many slight modifications are introduced into the old process, the resulting vinegar showing quite different qualities as regards odor and flavor.

Vinegar obtained from dilute alcohol will show a difference in odor depending on the material used in the preparation of the specific alcohol.

Potato alcohol always contains fusel oil and in the oxidation of the alcohol by the vinegar ferment, this oil is oxidized, giving characteristic flavor to the vinegar. Vinegar

prepared from wine, fruit, beer and glucose also possesses definite properties as regards odor, flavor, etc.

In preparing vinegar by the old process the first step is the alcoholic fermentation. In case of cider the juice is allowed to stand in casks until it has undergone alcoholic fermentation, and active fermentation has stopped. In most cases it is then racked off into other casks and left exposed to the air till sufficient acidity has developed to render it suitable for use. The above is a long, slow process, several months being required for the preparation of the finished article it being a well-known fact that the vinegar ferment required free access of air. Schützenbach in 1823, conceived the idea that if he greatly enlarged the surface which was exposed to the air, the process of acetification would be greatly hastened. His experinents were successful, and the so-called "quick process" was soon adopted. The process consists in allowing alcoholic liquid to trickle slowly through beechwood shavings packed into a cylindrical tower, so arranged as to allow a current of air to pass through it. This arrangement presents in a high degree all the conditions required for the formation of vinegar. The vinegar ferment being spread evenly on the surface of the shavings enables the process to take place simultaneously on many thousands of square feet, instead of the limited area of the tank as in the old process. The term quick process is very appropriate; it differs from the old process only in the time required for its execution, the chemical changes being the same in both cases. In carrying on the quick process, each manufacturer introduces slight modifications suggested by his experience or convenience, but the following description will give a general idea of the process.

Cider Vinegar.—The cider is put in large store vats and left quiet until the vinous fermentation has taken place. It is then what would be called hard cider and contains alcohol and some acetic acid. It is then known as "stock." When the stock is ready for the generator it is pumped into the filter. This may be of sand, sawdust or other fil

tering material, its object being to remove any sediment or floating organic matter which would otherwise clog the converters. From the filters it runs into the generators. The liquid is run through a screen at the top of the generator to break it up into drops and distribute the liquid evenly over the surface of the shavings. The generator consists of a round tank of wood six to ten feet high, with a diameter of 35 inches at the top, and 45 inches at the bottom, thus giving it the form of a truncated cone. The generator is divided into three parts one above the other; the upper one containing a screen to distribute the alcoholic liquor; the center one containing beech shavings, and the lower one serves for the collection of the vinegar. Air is let in by holes bored through the sides of the tank below the false bottom on which rest the beech shavings. The amount of air is regulated by wooden stoppers placed in these holes. After passing through the generator, if it contains any unconverted alcohol, the vinegar is passed through a second time, and then is finished vinegar. Many substances have been prepared for filling the generators, but at present beechwood shavings are considered the best. They are now made especially for this purpose, being cut and curled by machinery. They are prepared for the generator by being washed in water and steamed to remove the woody taste and impurities which they would otherwise give the vinegar. The shavings are dried and saturated with old vinegar and are then ready for use.

Brannt states that the surface exposed in a generator three feet by six, filled with shavings, is over 22,000 square feet.

Material for Vinegar Making.- The substances from which vinegar is made at the present time are beer, wine, glucose, alcohol, molasses, and fruit juices. Wine vinegar is chiefly used in Europe. It is made from grape juice, inferior wines and from the second and third pressings of the grapes called "lees." Wine vinegars vary in color from pale yellow to red, and have a specific gravity of from 1.014 to 1.022. Most of the vinegar used in Great Britain is derived from the fermentation of a wort made

from a mixture of barley and malt. Malt vinegar is of a decided brown color, and in specific gravity varying from 1.017 to 1.019, the strongest known as proof vinegar, containing from 4.6 to 5 per cent. of acetic acid. Glucose vinegar is prepared from a mixture of glucose and water, by allowing it to undergo alcoholic fermentation, and then running it through the generator in the usual way. The vinegar sometimes contains large quantities of dextrine and sulphate of lime, left in the glucose as an impurity during the process of manufacture.

Molasses vinegar is made in the same way as glucose vinegar.

The larger part of the vinegar now on the market is made from a dilute alcohol. This vinegar as it comes from the converters is colorless as water. It is colored by the addition of burnt sugar (caramel) and sold as cider vinegar.

Evapor

Characteristics of Different Vinegars.- Cider vinegar should have a yellow color and a cider-like odor. ated to dryness on a water bath it leaves a dark brown residue, having a taste of burnt apples. The amount of extract is from 1.5 to 5 per cent., depending on the age of the sample and method of manufacture. Cider vinegar made by the old process contains malic acid, and on the addition of acetate of lead gives a heavy yellowish precipitate of malate of lead. The ash from cider vinegar contains considerable quantities of alkaline phosphate. The residue from wine vinegar contains the salts found in wine. It is distinguished from other vinegars by containing cream of tartar. According to the Edinburgh Pharmacopoeia, it may be distinguished from malt vinegar by adding ammonia in slight excess, which causes in wine vinegar a purplish muddiness and slowly a purplish precipitate, but in malt vinegar no precipitate or only a slight one.

Spirit vinegar made from dilute alcohol should leave only a very small residue; if caramel has been added to color it the residue will be of a dark black brown and leave no ash on burning.

Beer vinegar is yellow and has an odor of sour beer.

contains as much as 6 per cent. of solids on evaporation. Beer vinegar does not contain more than 2.5 to 3 per cent. of acetic acid and requires to be fortified by the addition of a stronger vinegar. Glucose vinegar has the taste and smell of fermented grain. It usually contains considerable impurities, such as dextrine, sulphate of lime and sometimes sodium chlorides.

Adulteration of Vinegar.- Blythe classifies the adulteration of vinegar as follows:

1, Water; 2, mineral acids, usually sulphuric, rarely hydrochloric or nitric; 3, metallic adulterations; or, more properly, impurities as they are introduced from the apparatus. There are arsenic, derived from the sulphuric acid; copper, lead, zinc and tin from the solvent action of the acetic acid on any metallic surfaces with which they may come in contact; 4, Pyroligneous acid; 5, various organic, such as coloring agents, capsicum, etc.

The chief adulteration is the addition of whiskey vine. gar to cider vinegar, or the coloring of whiskey vinegar with caramel, and selling it for cider vinegar.

The analysis of a sample of vinegar consists in a determination of the specific gravity, the amount of acid present and total solids. The specific gravity is taken by a Westphal balance. To determine the acidity 20 c. c. are measured into a beaker, 100 c. c. of water and a few drops of phenol-phthalein (in alcoholic solution) are added, and the acid titrated with a normal alkali solution. The solids are found by evaporating 20 c. c. to dryness at 100° C. (212° F.) Thus far no free acid other than acetic or other impurities have been found in Wisconsin vinegar.

The following table gives the analyses of vinegar examined: