| 摘要 |
Prodn. of stable sulphide solns. in low concn., avoiding impairment by dissolved oxygen, pref. in a concn. range of 0.1-10 mg/1 is achieved by adding thiol complexes of As, Sb or Sn in amts. such that the dissociation of the dissolved complex gives the required concn. of free sulphide ions.The complex is pref. an alkali or ammonium salt of the formula (MeXS) (in which Me is alkali metal or ammonium, X is the central atom and n and m are determined by the valency of the central atom and the co-ordination no. of the complex), e.g. NaAsS2, Na3AsS3, Na3AsS4, NaSbS2, Na3SbS3, Na3SbS4, Na2SnS3 and Na2SnS4. The complex pref. is dissolved in NaOH solution, with addn. of ascorbic acid as antioxidant.The stable solns. are used as standards for monitoring the sulphide concn. in waste liquors and surface water, using ion-sensitive electrodes. The sulphide concn. of the solns. does not decrease by more than 5% in 12 days, in contrast to that of solns. of Na sulphide.
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