If 0.5 Gm. of Zinc Stearate be heated with a mixture of 9.5 Cc. of distilled water and 0.5 Cc. of hydrochloric acid, stearic acid will be liberated and float. as an oily layer on the surface of the liquid. If, after filtering this liquid through a small wetted filter, all of the zinc be precipitated by ammonium sulphide T.S., the filtrate should leave no fixed residue on evaporation (absence of alkalies, alkali earths, etc.). If 0.5 Gm. of Zinc Stearate be heated with a mixture of 9.5 Cc. of distilled water and 0.5 Cc. of nitric acid, and filtered, the filtrate should not become more than slightly turbid upon the addition of silver nitrate T.S. (absence of more than traces of chlorides). If 1 Gm. of Zinc Stearate be boiled with 50 Cc. of distilled water containing 2 Cc. of nitric acid, and filtered through a wetted filter, after thoroughly washing the precipitate with boiling water, the filtrate and washings, when evaporated to dryness and ignited, should leave a residue weighing not less than 0.14 Gm. and not more than 0.16 Gm. It should contain, in uneffloresced crystals, not less than 99.5 percent. of pure Zinc Sulphate [SO,. O,Zn + 7H2O], and should be kept in well-stoppered bottles. Colorless, transparent, rhombic crystals, or a granular crystalline powder, without odor, and having an astringent, metallic taste. Efflorescent in dry air. Completely soluble in 0.53 part of water at 25° C. (77° F.), and in 0.2 part of boiling water; soluble in about 3 parts of glycerin; insoluble in alcohol. When rapidly heated, the salt melts. At a higher temperature it is partly decomposed, losing both water and sulphuric acid. When very gradually heated to 50° C. (122° F.), it loses 5 molecules of its water of crystallization (31.2 percent.) without melting. At 100° C. (212° F.) a sixth molecule is lost, while the last is removed, with decomposition of the salt, at a temperature of about 240° C. (464° F.). Its aqueous solution shows an acid reaction with blue litmus paper. The aqueous solution of the salt (1 in 20) yields a white gelatinous precipitate with potassium ferrocyanide T.S., and a white precipitate with ammonium sulphide T.S., and with barium chloride T.S. If a small portion of the salt be moistened with a drop of cobaltous nitrate T.S., and heated before the blow-pipe, it will assume a vivid green color. The aqueous solution of Zinc Sulphate (1 in 20), after being acidulated with hydrochloric acid, should not respond to the Time-Limit Test for arsenic, cadmium, lead, and copper (see Appendix, Test No. 121); in applying this test the addition of ammonia water should be omitted. The aqueous solution should yield, with ammonium carbonate T.S., a white precipitate, which should redissolve completely in an excess of the reagent. The aqueous solution (1 in 20) should not be rendered more than slightly turbid by silver nitrate T.S. (limit of chloride). If 1 Gm. of Zinc Sulphate, in small fragments, be agitated for some time with 10 Cc. of alcohol, the filtrate should not redden moistened blue litmus paper (absence of free acid). Average dose.—Emetic, 1 Gm. (15 grains). ZINCI VALERAS Zinc Valerate Zn(C,H,O2)2 + 2H2O= 301.28 [ZINCI VALERIANAS, PHARM. 1890] It should contain not less than 99 percent. of pure Zinc Valerate [(CH,.COO)2Zn + 2H2O], and should be kept in small, well-stoppered bottles. White, pearly scales, having the odor of valeric acid, and a sweetish, astringent, and metallic taste. On exposure to the air, it slowly loses valeric acid. Soluble in about 50 parts of water, and in about 35 parts of alcohol at 25° C. (77° F.); somewhat more soluble in absolute alcohol. Boiling renders the aqueous solution turbid from loss of acid and formation of a basic salt. When heated, the salt melts. At a higher temperature it is decomposed, giving off inflammable vapors, and finally leaving a residue of zinc oxide. Its aqueous solution reddens blue litmus paper. If 0.5 Gm. of Zinc Valerate be dissolved in a mixture of 0.5 Cc. of hydrochloric acid and 9 Cc. of water, the valeric (isovaleric) acid will be liberated and float as an oily layer on the surface of the liquid. After filtering through a small wetted filter, the clear solution should not respond to the Time-Limit Test for arsenic, cadmium, lead, and copper (see Appendix, Test No. 121); in applying this test the addition of ammonia water should be omitted. If 0.5 Gm. of Zinc Valerate be dissolved in a mixture of 0.5 Cc. of nitric acid and 4.5 Cc. of distilled water, and the mixture filtered through a small wetted filter, the filtrate should show but a faint cloudiness upon the addition of either barium chloride T.S. (absence of sulphate) or silver nitrate T.S. (absence of chloride). Zinc Valerate should dissolve without residue in ammonium carbonate T.S. If 0.5 Gm. of Zinc Valerate be triturated with 3 Cc. of water, and 0.2 Cc. of ferric chloride T.S. added, the filtrate should not show a red color (absence of acetate). If a concentrated solution of copper acetate in water be added to a concentrated aqueous solution of Zinc Valerate, the mixture should remain perfectly clear (absence of butyrate). If 0.5 Gm. of Zinc Valerate be heated with a mixture of 9.5 Cc. of distilled water and 0.5 Cc. of hydrochloric acid and filtered, the filtrate should not respond to the Modified Gutzeit's Test for arsenic (see Appendix, Test No. 17). Average dose.-0.125 Gm. = 125 milligrammes (2 grains). ZINCUM It should contain not less than 99 percent. of pure metallic Zinc. A bluish-white metal, showing a crystalline fracture; in the form of thin sheets, or in irregular, granulated pieces, or moulded into thin pencils, or in fine powder, and having a specific gravity ranging from 6.9 when it is cast to 7.2 after it is rolled. Soluble in diluted sulphuric or hydrochloric acid with evolution of hydrogen. When heated above 100° C. (212° F.) and not above 150° C. (302° F.), the metal becomes malleable and ductile; above 200° C. (392° F.) it becomes suf ficiently brittle to be powdered in an iron mortar; at 412° to 415° C. (773.6° to 779° F.) it melts, and at 940° C. (1724° F.) it boils and may be readily distilled. If 1 Gm. of Zinc be added to 20 Cc. of diluted hydrochloric acid, the liberated hydrogen should not have a disagreeable odor, nor should it color a strip of paper moistened with lead acetate T.S. (absence of sulphur), or with silver nitrate T.S. (absence of arsenic, antimony, and phosphorus). The resulting solution should be clear and colorless, and should yield a white gelatinous precipitate with potassium ferrocyanide T.S., and a white precipitate with ammonium sulphide T.S. If 1 Gm. of Zinc be dissolved in a mixture of 10 Cc. each of nitrohydrochloric acid and water, the solution evaporated to dryness, the residue moistened with 2 Cc. of hydrochloric acid and again evaporated, and the final residue dissolved in 10 Cc. of water, this solution should not respond to the Time-Limit Test for arsenic, cadmium, lead, and copper (see Appendix, Test No. 121); in applying this test the addition of ammonia water should be omitted. ZINGIBER The dried rhizome of Zingiber officinale Roscoe (Fam. Zingiberaceœ). Laterally compressed, irregularly branched pieces; externally whitish or pale buff, longitudinally striate; fracture short-fibrous, mealy, showing numerous small oil and resin cells and circular groups of fibrovascular bundles; odor agreeably aromatic; taste aromatic and pungent. Average dose.-1 Gm. (15 grains). APPENDIX PAGE I. TESTS, REAGENTS, TEST SOLUTIONS AND VOLUMETRIC SOLUTIONS Introductory Tests, Reagents and Test Solutions Indicators for Acidimetry, Alkalimetry, etc. ..... Volumetric Solutions II. ALPHABETICAL LIST OF VOLUMETRIC ASSAYS.. 517 517 518 541 544 569 VI. LIST OF THE ELEMENTS AND PRINCIPAL PHARMACOPEIAL CHEMICALS.. 582 |