This common article of consumption is frequently contaminated by copper. This deleterious quality it obtains from the mode of its manufacture, as well as from the articles from which it is manufactured. The usual way in which it is prepared is by boiling in a copper the residue left in the still of the vinegar manufacturer, with a decoction of the outer green shell of the walnut (previously prepared also by having been boiled in a copper, in combination with common salt;) together with a portion of allspice or pimento, pepper dust, (or cayenne pepper, should the manufacturer be a _man of taste_;) and garlic. The method of detecting the fraud is detailed at page 294 of Mr. Accum’s book: it is too long for insertion here. ISINGLASS. Isinglass, which is prepared from the air-bladders of the sturgeons, is the subject of sophistication. The dried bladders of horses, the skins of soles, and the intestinal membranes of calves and sheep are frequently sold for it. The fraud may be detected by boiling the shreds in water; when, if the article is adulterated, the spurious ingredients will obtain only an imperfect insolubility, whereas genuine isinglass is almost perfectly soluble in water. Isinglass to be good, should be white, perfectly transparent, dry, fibrous, and of a faint odour and insipid taste. The best variety occurs in the form of a lyre or horse-shoe; the worst, flat, in the form of a pancake. The saltish taste of fictitious isinglass is also another of the criteria for judging of its goodness. BLUE OR INDIGO. This article is subject to great adulteration by the introduction of foreign ingredients into its manufacture. The easiest and speediest test of its genuineness is by dissolving or cutting it. By the first method, if good, it dissolves easily, while that of a coarse or an adulterated kind dissolves with difficulty, and settles at the bottom of the vessel. By the second method, (and which is the best criterion of its goodness,) when cut with a knife, it exhibits a red copper-like appearance. Where this shade is absent or only very slight, the indigo is of an inferior quality.—Other signs of its goodness are that it should be light, of a close texture, break easily, float on water, be free from white specks or sand, and from white adhesive mould externally, and when rubbed with the nail, it should have a shining copper-like hue. SOAP. Soap is subject to great adulteration, as every person is aware who has had an opportunity of witnessing the specimens made twenty years ago, before “Messieurs les Artistes” had made their prodigious advances, as our “YANKEE” brethren across the Atlantic phrase it, “in the _progressing_ knowledge of the age.”