Notes on analytical chemistry for students in medicine : extracted from the fifth edition of "Notes for students in chemistry" / by Albert J. Bernays.

  • Albert Bernays
Date:
1889
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Licence: Public Domain Mark

Credit: Notes on analytical chemistry for students in medicine : extracted from the fifth edition of "Notes for students in chemistry" / by Albert J. Bernays. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

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    TESTS FOB CARBONATES AND SULPHIDES. The important salts discoverable by the Group-test A. HC1. are: Carbonates, Sulphides, Sulphites, Thiosulphates, Nitrites, Chlorates, Hypochlorites, Hypobromites, Acetates, Cyanides, Arsenites, Cliromates, Silicates. I. Carbonates. Those of the alkaline metals alone soluble in water. Solutions colorless: alkaline to test-paper. The Hydro- carbonates, or bi-carbonates, KHC03, NaHC03, and NH,HC03, are also alkaline: when solutions warmed, they evolve C02, with effervescence. All bi-carbonates of the metals somewhat soluble and precipitated, when boiled, as carbonates. The common soluble Carbonates are: 2KjC03,3H20. KHC03. Na2CO3,10H2O. NaHC03.. 2[(NH4)2C03],C02. A. HCl, effervescence from escape of inodorous C02, which can be decanted into a test-glass containing Lime-water, and yields ppt. of CaC03. BaCl2, white ppt. of BaC03, soluble with effervescence in HC1. AgN03, white ppt. of Ag2C03, soluble with effervescence in HN03, and also soluble in NH4HO. * Solution of Ma2G03, precipitates solution of Magnesium sulphate at once as white carbonate; but, solution of NaHC03, only on standing, or immediately on warming. Carbon dioxide C02, a colorless gas, inodorous, soluble in water measure for measure. Its solution in water turns litmus paper port-wine red, evolves pearly bubbles of gas on heating, precipitates lime-water, and leaves no residue on evaporation. Hypothetical Carbonic acid H2C03. Prep, of C02. CaC03 + 2HC1 = CaCI2+ H^O + CO,. II. Sulphides. Yellow, or colorless. Smell of H2S. Alkaline to test-paper. Those of Groups V. and VI., among the metals, alone soluble in water. The common soluble sulphides are: NEL.HS, (NH4)2S, (NH4)2S2. A. HCl evolves H2S, which browns or blackens'lead-paper. In the higher Sulphides, or Polysulphides, HCl precipitates Sulphur of white or yellow color, and evolves H2S with effervescence and characteristic odor. AgN03, black Ag2S, insoluble in Ammonic hydrate. Fe2Cl,„ black sulphide. Nitroprusside of sodium, Na2Fe(NO)Cyfi, rich violet color (none with H2S). Hydrogen sulphide, H2S, in solution in water, is recognized by its odor of putrid eggs, and acidity to test-paper. Either colorless, or slightly milky from Sulphur. Blackens lead-paper. No residue on heating. Prep. FeS + H2SO., = FeSO., + H2S. A. HCl, no reaction. HCl -1- H2S is No. II. Group-test (pp. 18-25) precipitates many metallic Sulphides, and does not re-dissolve them.