Zinc oxinate equilibrium solution

Accordingly, if a solution of a zinc salt is treated with an excess of hydroxy-quinoline and the precipitate is removed by filtration, the clear filtrate consists of the zinc oxinate equilibrium solution, from which fluorescent zinc oxinate can be precipitated by hydroxyl ions and consequently also by contact with ammonia vapors. Quantities of zinc oxinate which are too slight to give a visible turbidity nevertheless yield an easily discernible fluorescence. 

Reagent Zinc oxinate equilibrium solution 1 % aqueous solution of zinc chloride is treated with excess 1 % alcoholic solution of 8-hydroxyquinoline and the precipitate is filtered off. The reagent solution keeps. 

When 8-hydroxyquinoline (oxine) (I) is added to an ammonical or caustic alkaline solution of a zinc salt, there is quantitative precipitation of the light yellow crystalline zinc oxinate(II), which displays a yellow-green fluorescence in ultraviolet light. The precipitate is readily soluble in excess mineral acid. Consequently, the precipitation of zinc oxinate from neutral solutions of zinc salts is incomplete because of the rapid establishment of the equilibrium ... 

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See also in sourсe #XX -- [ ]

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