Vinegar is prepared from a variety of substances; but its common preparations are from wine, fruits, malt, sugar, and wood. The vinegar made from wood is the strongest, containing at least eight times the strength of the common preparations. It is perfectly colourless, and its taste is very pungent and grateful. But the vinegar generally prepared for sale in this country is made from malt; which to be good should be of a pale brown colour, perfectly transparent, of a pleasant and rather pungent acid taste, but without acrimony, and a fragrant grateful odour. These are the readiest and best tests of good vinegar. But as a false strength is frequently given to it by adding oil of vitriol, sulphuric acid, or the extract of some acrid vegetable, as pellitory of Spain, capsicum, &c. or metallic extracts, the tests for ascertaining these foreign substances are as follow: If it is suspected that vinegar is adulterated with oil of vitriol, put three or four drops of acetate of barytes into a glass of vinegar; filtrate the white precipitate thereby produced through paper, and heat the powder or residuum remaining in a tobacco-pipe until it is red hot. Then put it into spirit of salt or diluted aqua-fortis; if the precipitate dissolves, the vinegar is genuine; if not, it is adulterated. But if metallic adulteration is suspected, add liquid ammonia to the vinegar, until the odour of the ammonia predominates; if the mixture assumes a blackish tint, it is a sign that copper is present in the article. If the presence of lead be suspected, add water impregnated with sulphuretted hydrogen to the suspected vinegar; if the mixture becomes black or yields a black precipitate, your suspicion is well founded. OLIVE, OR FLORENCE OIL. Olive oil is frequently adulterated by mixing with it the oil of poppy seeds or a decoction of cucumbers, which latter ingredients easily unite with the oleaginous substances. It is frequently impregnated with lead, from the circumstance of the fruit which yields the oil being compressed between leaden plates, and the oil being suffered to remain in pewter or leaden cisterns in order to become clear before it is offered for sale. This last injurious quality is communicated afresh to the commodity by the retail venders, who frequently keep a pewter vessel immersed in the oil, for the purpose, as they assert, of preserving the liquid from becoming rancid. It is however proper to state that the metallic contamination by the wholesale manufacturer chiefly belongs to the Spanish produce: the French and Italian manufacture is usually free from the impregnation.