Aqua Picis Liquidae.—Tar Water.
Related entry: Pix Liquida (U. S. P.)—Tar
Preparation.—Take of tar, 2 pints; boiling water, 1 gallon. Mix together and stir with a wooden rod for 15 minutes. When cold, and the tar has subsided, strain the liquor and keep it in well-stoppered bottles (Dub.). The German Pharmacopoeia prepares it by mixing with previously washed and dried pumice stone (3 parts), tar (1 part). Of this mixture add 2 parts to 5 parts of water, shake well for 5 minutes and filter. It forms a clear yellow or yellow-brown fluid.
Description, Medical Uses, and Dosage.—Tar water has a Madeira-wine color, and a sharp, empyreumatic taste; it reddens litmus, but does not effervesce with carbonate of potassium, though it becomes more darkly colored. Persulphate of iron blackens it. It consists of water, holding in solution acetic acid, resin, and pyrogenous oil. Tar water exerts a mild influence on mucous membranes, and hence has been found useful in chronic catarrhal and urinary affections, in doses of 1 or 2 pints daily. Sometimes tar water is prepared, with the addition of honey, for pulmonary affections. Externally, it has been found useful as a wash in diseases of the scalp, and other chronic affections of the skin. The usual dose is from 1/2 to 1 fluid ounce.