This section is from the book "The Manufacture Of Liquors, Wines, And Cordials, Without The Aid Of Distillation", by Pierre Lacour. Also available from Amazon: Manufacture of Liquors, Wines, and Cordials, Without the Aid of Distillation.
A Test for Arsenic. - Nitrate of silver, forty-four grains; dissolved in water, one ounce; add gradually, weak water of ammonia, till a mere trace of the undissolved nitrate of silver remains. A few drops of this added to a solution, composed of two parts of sulphuric acid and one of distilled water, or water entirely free of impurities, such, for instance, as recent rain water, and if any traces exist of arsenic, it will be indicated by a pale, yellow precipitate, or a chocolate red.
If a few drops of the test yield no color, an additional quantity should be added, and then examine closely for traces of arsenic.
Sulphuric acid is largely employed in adulterating vinegar; for giving to it the necessary sharpness or acidity. Vinegars prepared upon a cheap scale for auctions, in all large commercial cities, will exhibit, upon analysis, an astonishing amount of free sulphuric acid - a small volume of acetic acid being added to conceal a taste peculiar to the sulphuric acid when in solution - and also to furnish the necessary odor of vinegar. This acid is also used in the manufac ture of lemon syrup, and the acidulated syrups generally, cherry brandy and cherry bounce, in the different brands of bitters, to prevent the fermentation that would otherwise ensue, owing to a deficiency of alcohol in these bitters when prepared upon a cheap scale.
Take a long glass case, or arrange any kind of a box that admits the heat and light, and arrange shelves in it a few inches apart, one above the other; on them place plates, or flat earthenware, or wooden dishes - taking care that the dishes are not glazed with red lead - then fill these dishes with alcohol, and suspend over each dish a portion of platina black; then hang strips of porous paper in the case, with their bottom edges immersed in the spirit to promote evaporation. Set the apparatus in a light place, at a temperature of from 68° to 86° Fahr., for which purpose the heat of the sun will be found convenient. In a short time, the fermentation of vinegar will commence, and the condensed acid vapors will be seen trickling down the sides of the glass, and collecting at the bottom. We shall find, during this process, produced by the mutual action of the platina and the vapor of alcohol, there will be an increase of temperature which will continue till all the oxygen contained in the air inclosed in the case is consumed, when the acetification will stop. The case must be open for a short time, to admit of a fresh supply of air, before the operation will re-commence.
With a case of twelve cubic feet content, and six ounces of platina powder, one pound and one eighth of absolute acetic acid can be produced from one pound of alcohol; and if we estimate the product by the strength of vinegar, the product will be great. From twenty-five pounds of platina powder, and three hundred pounds of alcohol, three hundred and fifty pounds of the pure acid may be produced daily.
The platina powder does not waste, and the most inferior spirit may be employed.