writing, as in ignorance of this relative valuation of the drop a larger dose may be ordered than is desired by the practitioner, or than the welfare of the patient demands. Approximate Measurements, With the varying dimensions of teaspoons, tablespoons, wineglasses, etc., depending on the caprices of fashion or the fanciful manipulation of the silversmith or the glassmaker, no absolutely exact quantity can be fixed upon as the definite contents of any one of these articles. Custom, not law, has decided only approximately the measurement of each, and the practitioner can merely indicate, in a general way, the dose which he wishes to be administered to his patient, although the latter's modern. teaspoon may sometimes be nearly as large again as the old-fashioned ones of his ancestors. A wineglassful is a very uncertain quantity, but when such a dose is employed, it is usually that of an infusion or decoction, which does not require absolutely exact measurement of the dose. Indeed this quantity is comparatively seldom prescribed in the United States, not nearly so often as by some of our transatlantic brethren. SOLUBILITY OF MEDICINES IN WATER, The practitioner is hardly sufficiently armed with a proper knowledge of the art of prescribing who is not informed as to the solubility of the substances which he is about to employ. The young prescriber, especially, is often embarrassed as to the effective solution of the articles he may wish to introduce into his prescription; shall it be an alcoholic or an aqueous solution, and, if so, is the substance soluble in one or the other, and are the other ingredients miscible with it? Such are the questions he often asks himself, and the accompanying table, which includes all the prominent remedies, will supply the answer. Even those who are experienced prescribers and dispensers will find such a summary valuable for daily use. The table has been carefully prepared by the author from results arrived at in the researches of various undoubted authorities,' and offers the advantage of immediate and ready reference at the moment it is needed. For much of the information here conveyed the practitioner might search his text-books in vain. The works on chemistry proper, of course, take no cognizance of the solubility of purely medicinal agents, and medicochemical treatises content themselves with only a brief mention of the solvent powers of such a useful excipient as glycerine. There are many opportunities, indeed, for Pharmacopoeia of the United States, 1873; United States Dispensatory, 14th edition, 1877; Frank H. Storer, First Outlines of a Dictionary of Solubilities of Chemical Substances, 1864; etc. the employment of these solutions in glycerine, both externally and internally, which are neglected from the usual inaccessibility of such information. No allusion is made in the following table of solubilities to such articles of the materia medica as give up only a portion of their virtues to alcohol, water, etc., leaving undissolved a considerable amount of residue. We shall allude to preparations formed in this way, such as tinctures, in another place. (See Pharmacopoeial Groups.) Nor is mention made of the solubility of substances in acids, when such solution is really nothing less than actual decomposition or disintregration, sometimes amounting to the formation of a salt with totally different properties. The solvents referred to in the table are those which are of constantly recurring interest to the physician and the pharmaceutist, being those most commonly resorted to by the former in prescribing, and by the latter in compounding. The solvent powers of these menstruawater, alcohol, ether, glycerine—are exerted in a discrimi nating way, for which we can offer no satisfactory expla nation, some substances being soluble either in water or alcohol, while others of a somewhat similar chemical nature are insoluble in one or both of these fluids. Very few articles employed by the practitioner are wholly insoluble. Solubility of Medicines in Water, Alcohol, Ether, Glycerine, etc. lacticum Soluble. ...... Soluble. Soluble in 9 times its Soluble in Moderately solu- Solub. with| Soluble. weight. its weight. ble. difficulty. Soluble. Soluble. Insoluble in fixed and ...... volatile oils. 100 parts of glycerine dissolve 50 parts. tartaricum Soluble in rather less Soluble in Soluble. Insoluble. than its weight. its w❜ght. |