Chemistry: general, medical, and pharmaceutical : including the chemistry of the U. S. pharmacopoeia. A manual on the general principles of the science, and their applications in medicine and pharmacy.

  • Attfield, John.
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: Chemistry: general, medical, and pharmaceutical : including the chemistry of the U. S. pharmacopoeia. A manual on the general principles of the science, and their applications in medicine and pharmacy. Source: Wellcome Collection.

Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.

    142/700 (page 132)
    duct with a small quantity of cold distilled water, draining and drying by exposure to air at ordinary temperatures. Valerianate of zinc is soluble in ether, alcohol, or hot water. ZnS04 + 2NaC5He02 = Na2S04 + Zn2C5H902 Sulphate Valerianate of Sulphate of Valerianate of zinc. sodium. sodium. of zinc. Note.—The compounds of zinc described in the above six reac- tions are the only ones mentioned in the British Pharmacopoeia ; the processes are also those of that work. Sulphide and Hydrate of Zinc are mentioned in the following analytical paragraphs. The formula of Sulphite of Zinc is ZnS03,3H20. (b) Reactions having Analytical Interest ( Tests). First Analytical Reaction,—To solution of a zinc salt (sulphate, for example) in a test-tube, add solution of sul- phydrate of ammonium (NH4HS); white sulphide of zinc (ZnS) is precipitated, insoluble in acetic, but soluble in the stronger acids. Note.—This is the only white sulphide that will be met with. Its formation, on the addition of the sulphydrate of ammonium, is there- fore highly characteristic of zinc. If the zinc salt contains iron or lead as impurities, the precipitate will have a dark appearance, the sulphides of those metals being black. Hydrate of aluminium, which is also white and precipitated by sulphydrate of ammonium, is the only substance sulphide of zinc is likely to be mistaken for, and vice versa .but, as will be seen immediately, there are good means of distinguishing these from each other. Second Analytical Reaction.—To solution of a zinc salt add solution of ammonia ; white hydrate of zinc (Zn2HO) is precipitated. Add excess of ammonia; the precipitate is redissolved. This reaction at once distinguishes a zinc salt from an aluminium salt, hydrate of aluminium being insoluble in ammonia. Other Analytical Reactions.—The fixed alkali-hydrates afford a similar reaction to that just mentioned, the hydrate of zinc redissolving if the alkali is free from carbonate. Carbonate of ammonium }ields a white precipitate of car- bonate and hydrate, soluble in excess. The fixed alka- line carbonates give a similar precipitate, which is not redissolved if the mixed solution and precipitate be well boiled. Ferrocyanide of potassium precipitates white ferrocyanide of zinc (Zn.2FeCy6). Sulphate of magnesium, which is isomorphous with and