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I have a year old bottle of ferric chloride in my basement for PCB etching that I realized that I was never going to use. What is the best way to make sure that it is neutralized without pH paper or cabbage for testing?

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You can add powdered calcium carbonate (limestone) until the liquid component was clear upon settling or until the addition of calcium carbonate did not produce additional bubbling. Calcium carbonate is ideal because it is cheap, neutralizes acids to a non-corrosive pH with no need to measure, and is not itself caustic.

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