Foeskes
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Will nickel(II) hydroxide react with sodium hypochlorite or hydroxide?
I am going to try to separate nickel from chromium.
I'm thinking of using either reacting their hydroxides(Ni(OH)2 and Cr(OH)3) with sodium hypochlorite or sodium hydroxide to dissolve the chromium and
precipitating the nickel hydroxide. Although the I'm not sure if the nickel hydroxide will react with those or if the chromium has trouble dissolving
or something, since I can't really find that much information on it.
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ninhydric1
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Nickel hydroxide shouldn't dissolve in NaOH solution, but chromium hydroxide will react with NaOH to form sodium chromate.
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Foeskes
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Doesn't Sodium hydroxide react to form chromite?
And what about hypochlorite?
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ninhydric1
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Chromates are chromites, just that chromate is the more common and more widely used nomenclature. Sodium hypochlorite will also dissolve chromium
oxide. Note that these reactions occur slowly so adding hydrogen peroxide will speed the reaction up.
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woelen
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Sodium hypochlorite reacts with nickel hydroxide. A black insoluble compound is formed, most likely a nickel(III) compound. I think it is hydrous
Ni2O3.
Sodium hypochlorite also reacts with chromum hydroxide. It reacts with formation of a yellow solution of sodium chromate. This contains hexavalent
chromium in the CrO4(2-) ion.
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wg48
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Nickel chromate is insoluble. So some of the nickel hydroxide may be converted nickel chromate in the presence chromate ions. Perhaps with a high ph
(large excess of alkali) it will not be very much or sufficiently slow that reasonable separation of the soluble chromate can still be achieved.
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Foeskes
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So is sodium hydroxide the most ideal for dissolving the chromium and leaving the nickel behind?
According to Wikipedia:chromites are chromium in its third oxidation state(Na2Cr2O4) and chromates are chromium in its sixth(Na2CrO4)
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ninhydric1
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Oh, my mistake then. Chromium chemistry can be a bit confusing  .
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DraconicAcid
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Yes, separate chromium from nickel with sodium hydroxide.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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