CuSO₄とNiSO₄またはCoSO₄混合硫酸塩の水-エタノール混合溶媒に対する溶解度

抄録

The solubility curves of sulfates in the systems CuSO₄-NiSO₄-H₂O-C₂H₅OH and CuSO₄-CoSO₄-H₂O-C₂H₅OH at 298K were determined and the possibilities of industrial application of fractional crystallization method was discussed. The results are summarized as follows:
(1) The solubility curve for the system CuSO₄-NiSO₄-H₂O-C₂H₅OH can be devided into 2 portions which are characteristic to crystallization of CuSO₄.₅H₂0 and NiSO₄.7H₂0, respectively. Each crystalline phase contains only minute amount of other sulfate. The solubility of CuSO₄ at eutectic point decreases with increase in the concentration of ethanol from 0.78 to nearly zero, while that for NiSO₄ ranges from 2.18 to nearly zero.
(2) A similar solubility curve can be obtained for the solution system of CuSO₄-CoSO₄-H₂O-C₂H₅OH. However, the solid phase equilibrated with a saturated CoSO₄ solution was identified to be a mixed crystalline phase of (Co, Cu) SO₄.7H₂0.
(3) The separation of CuSO₄ from the saturated CuSO₄ solutions containing NiSO₄ up to 1 mole is possible to produce almost pure crystals of chalcanthite with the yield ranging 70 to 98%. The required amount of ethanol for the crystallization of chalcanthite ranges from 0.23 to 0.43 kg per kg of water, leaving the resultant solution whose CuSO₄ concentrations are 0.35 to 0.01 moles per kg of water.