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Name: Ian M.
Status: other
Age: old
Location: N/A
Country: N/A
Date: 2001 - 2002


Question:
Sir, I haven a substantial quantity of sulfuric acid, about 15 gallons, which I have been using to pickle (etch clean) copper parts that I have been making into a boiler for a steam locomotive. I have completed the work and I wish to dispose of the acid in a safe way. The solution is dilute in the approximate ratio of 1:15 acid/water. I tried household bleach but only succeeded in producing chlorine gas! A litmus test came up bright red and I am unwilling to go on making chlorine and I am asking if there is a suitable chemical alternative for baking soda, washing soda etc. Thanking you in anticipation.


Replies:
You are correct that household bleach is not an appropriate reagent for neutralizing sulfuric acid. Baking soda will work, but as you have already probably discovered, CO2 gas is produced and this makes a messy foam. The most direct method would be to neutralize the sulfuric acid with DILUTE sodium hydroxide, which you can probably obtain from a hardware store or industrial chemical supplier under the common name, "caustic soda". This should be diluted carefully with water because the heat of dilution is substantial. Add the diluted sodium hydroxide slowly to the dilute acid until the endpoint is reached using litmus paper. The reaction product is aqueous sodium sulfate, which can be safely discarded into the sewer/septic system.

A word of caution: Do NOT use "old fashion" Draino as a source of "caustic soda". It is a mixture of sodium hydroxide and aluminum flakes. When diluted hydrogen is evolved, which is potentially explosive.

Vince Calder



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