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I am owner/operator of a small plating company in Pittsburgh, Pa. I am having a problem with reddish color in brass plating process. Obvious cause is low zinc content in brass plating bath. Our solution is cyanide based, but zinc cyanide is expensive and the minimum order is more than I would use in a lifetime. A chemist suggested using zinc chloride in place of zinc cyanide, with an increased amount of potassium cyanide to act as bonding agent and carrier, with the resulting by product being potassium chloride. Potassium chloride, being mildly acidic, would need to be leveled to maintain proper pH. In theory I understand this solution and, again in theory, it should work. However, I do not wish to ruin my process if this solution does not work in practice. Any insight would be appreciated.

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    $\begingroup$ Potassium chloride is neutral, unless there are mildly acidic impurities in the salt or water. Zinc chloride is mildly acidic. It is supposed $\ce{ZnCl2}$ is added to excess of $\ce{KCN}$ as zinc cyanide $\ce{Zn(CN)2}$ is almost insoluble ( $\pu{0.00005 g/100 mL}$ at 20 °C.). The technician and/or the recipe must have meant rather potassium tetracyanozincate $\ce{ZnCl2 + 4 KCN -> 2 KCl +K2[Zn(CN)4]}$ It is also sold commercially. $\endgroup$
    – Poutnik
    yesterday

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