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Vinegar, Pickles, and Pickling: Distilled

To Clarify Vinegar. -To clarify vinegar for bottling, draw it off into a clean cask or other vessel and throw into it a handful more or less of VINEGAR, PICKLES, AND PICKLING shredded isinglass. Let it stand for few days and filter through a cheese cloth. a Distilled Vinegar. - Vinegar is distilled by heating in an ordinary retort by means of a sand bath, about 7 pints being carried over from each gallon. No lead or pewter can be used in any part of the retort or condenser, as the acetic acid acting upon these metals produces a poisonous compound. Distilled vinegar is weaker than the ordinary commercial article for the reason that water boils at a lower temperature than acetic acid.

Hence more water than acetic acid is carried over. Distilled vinegar is used principally by druggists.

Sub- To Decolorize Vinegar. stances recommended for this purpose are ivory black, bone black or ordinary charcoal, all of which have the property of absorbing the various coloring matters so as to reduce ordinary cider, red wine, or other highly colored vinegar to a limpid and transparent whiteness.

Mix with each gallon of red wine or cider vinegar about 6 ounces of pure bone charcoal, from which, by means of a coarse sieve, all loose dust and small grains have been removed.

Place the whole in a glass or earthenware vessel and shake or stir from time to time until the color has been removed.

Or the charcoal, in the same proportion, can be thrown into an ordinary cask, and the contents stirred occasionally.

Or if the cask is bunged up, the cask may be rolled or rocked, or ended up from time to time, to bring the charcoal in contact with all parts of the vinegar.

Or a double bag of any desired size may be made of coarse linen and lined with a layer of charcoal 2 or 3 inches in thickness. This should be quilted sufficiently to prevent the charcoal from settling or bunching up. Vinegar may be decolorized by straining through this.

Strength of Vinegar. -The strength of vinegar or the amount of acetic acid which is contained in different specimens, differs greatly. To determine the proportion of acetic acid, suspend 4 or 5 ounces, by weight, of broken pieces of fine marble in 16 ounces, by weight, of vinegar. The acetic acid will attack the marble and will be gradually neutralized.

Let stand overnight. Remove the marble, rinse it in cold water, dry it thoroughly with gentle heat on top of the stove (but take care not to melt it), and weigh it carefully, of its loss in weight is the quantity of actual acetic acid contained in the sample. And from this amount the proportion of acetic acid can be readily obtained.

Good vinegar should contain about 5 per cent of absolute acetic acid.

The commercial test is the number of grains of pure carbonate of potassium that will exactly neutralize 1 fluid ounce of vinegar. If 20 grains of carbonate of potassium are required, the sample is known as 20 grains' strength.

Purity of Vinegar. -Various mineral acids, as sulphuric, nitric, hydrochloric and others, are sometimes added to vinegar as adulterants to increase its acidity, and for other purposes. Red pepper, mustard, and other acrid substances are also used, and traces of copper and lead are sometimes derived from the vats or kettles in which the vinegar is prepared.

Test for Sulphuric Acid. Stir into a sample of suspected vinegar a small quantity of potato starch and bring to a boil. Remove from the fire and let stand until entirely cold. Add slowly, drop by drop, a solution of iodine. If the vinegar is pure, the iodine solution will produce the blue color of iodide of starch, but if sulphuric acid is present the starch will have been converted by boiling into dextrin, and the blue color will not appear.

Or dip a piece of writing paper in the vinegar and heat it over the stove; if the vinegar is pure, the paper will not be charred, but the presence of 2 per cent or more of sulphuric acid will char it. Or a more delicate test consists in bringing to a boil a solution of ounce of sugar in 16 ounces of water and when it reaches the boiling point dipping into it a china cup or saucer.

If a drop of vinegar is let fall on this china surface while moistened with sirup at the temperature of boiling water (212° F.) if pure it will produce no perceptible effect. But if it contains the slightest trace of sulphuric acid it will produce a spot of color ranging from pale green to a darker brown or black in proportion to the quantity of free sulphuric acid present.

Test for Hydrochloric Acid. - To test for hydrochloric acid use the boiled potato-starch and solution-ofiodine test for sulphuric acid; the reaction will be the same.

Or add to the suspected sample a little silver nitrate, which, if hydrochloric acid is present, will produce a white precipitate.

Test for Nitric Acid. - To test for nitric acid, add a solution of indigo to the sample of vinegar and bring to a boil. The nitric acid can be detected by a yellow color. Tests for Other Adulterants. - To discover the presence of red pepper, mustard, etc., boil down the vinegar until all the water it contains has been evaporated, when, if these substances are present, the resulting extract will have a sharp, biting taste. To test for copper, add potassium ferrocyanide, which will give a brown precipitate.

To test for lead, add hydrogen sulphide, which will give a black precipitate, or potassium iodine, which will produce a yellow precipitate.

To Strengthen Vinegar.

To strengthen a quantity of weak vinegar, boil down a gallon of good vinegar to 2 quarts, and let it stand in the sun for a week or ten days. Add this to about six times its own bulk of weak vinegar. The whole will be strengthened and given an agreeable flavor.