Hypochlorite

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Hypochlorite (ClO-) is an ion composed of chlorine and oxygen but in refining it is often used as a short name of sodium hypochlorite (NaClO, bleach)or calcium hypochlorite (CaClO, pool chlorine). Here it will be seen as a common name of the chemicals used in some gold leaching processes where the hypoclorite ion is the active part.

Dissolving gold

(Main article Dissolving gold with bleach)

One of the most common usage of sodium hypochlorite is to dissolve fine gold foils or powder, for example from gold fingers or the black powder from a reverse plating cell. By adding hydrochloric acid the pH is lowered enough to release chlorine that oxidizes the gold and makes it possible to dissolve it in the hydrochloric acid. The process is popular with hobby refiners as it doesn't demand nitric acid and there is no need for denoxing.

It works fine on thin foils and powders but is too slow to be practical on solid gold as shots or cornflakes.

Hypochlorite leach of ore

(Main article Leaching gold ore with hypoclorite)

References

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