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I have about 30 ml of leftover Sulfuric acid. There is a similar thread on this board suggesting ways to dispose of it. They involve adding baking soda after adding the sulfuric acid to water. However, the MSDS sheet for sulfuric acid contains the following statement which scares me: "A violent exothermic reaction occurs with water."

Any suggestions please.

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  • Why do you want to dispose of it? This stuff is very useful for many things. If you have 100% plastic drains, it's really good for clearing clogs. This is such a tiny amount, I'd just pour it down the drain. Might be able to give it away on craigslist. But, if it were me I wouldn't bother with picking up such a tiny amount.
    – maplemale
    Aug 17, 2015 at 18:08

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As my high school chemistry instructor made us learn:

Do as you oughta - add acid to water.

If you add water to acid, the reaction dynamics work out badly and you get the MSDS warning - the water boils, this spits acid solution all over, and is dangerous.

If you add acid to water, the reaction dynamics work in a more favorable fashion, and nothing exciting happens as you dilute the acid.

To further enhance safety, you can use cold water and chill the acid, though this is a bit more than is really needed.

Gloves and eye protection are always advisable.

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  • It may be worth noting that dilute sulfuric acid exposed to air can become more concentrated over time; an advantage of adding baking soda is that if one adds enough baking soda evaporation will no longer be able to make the resulting mixture to dangerously acidic, and no matter how much baking soda one adds the mixture can never become more basic than baking soda.
    – supercat
    Dec 16, 2015 at 18:45

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