These are official liquid medicines, formed with vinegar as a menstruum and charged by maceration with different medicinal principles. Many medicines contain active principles which are not readily taken up by water or alcohol, or are, perhaps, insoluble in them, but which are freely soluble in vinegar; others again, although soluble in water or alcohol, are not as efficient and energetic thus prepared, as when tinctured in vinegar; on this account, medicated vinegars are especially useful in many instances. The vinegar of commerce is very apt to contain impurities and elements which lead to its decomposition; hence, when used as a solvent for pharmaceutical purposes, distilled vinegar or diluted acetic acid should be preferred. The solvent property of vinegar chiefly depends upon its acetic acid, which renders it more especially valuable in the preparation of those agents, especially alkaloids, which are soluble in this acid, or which are rendered more soluble by being converted into acetates. Medicated vinegars are not permanent preparations; and to prevent their spoiling too rapidly, a small proportion of alcohol is usually added to them, which, however, necessarily gives rise to some acetic ether, besides being sometimes liable to cause precipitation; if the same proportion of concentrated acetic acid be substituted for the alcohol, the formation of the ether may be avoided, and the medicated vinegar be preserved equally as well. It is better to prepare this class of compounds only as they are required.