摘要 |
An 'onium salt, e.g. a quaternary ammonium salt, of an anionic dye maybe prepared by mixing an aqueous solution of a salt of the dye with a solution of a water-insoluble 'onium salt in an organic solvent, and separating a solution of the 'onium salt of the anionic dye in the organic solvent from the residual aqueous solution.
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