Safe disposal of sulphuric acid

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Safe disposal of sulphuric acid

Postby e^iπ+1=0 » Fri Feb 11, 2011 12:20 am UTC

A couple years ago I ordered some chemicals online and had fun with some fairly basic reactions. Apparently one of them involved sulphuric acid because I found a bottle of it in a corner of my room today. Guess I forgot about it... oops? It claims to be 98% concentration. The bottle is discolored on one side and it feels like it's slightly deformed. There's roughly .9 liters of it. How do I dispose of it safely?
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Re: Safe disposal of sulphuric acid

Postby ++$_ » Fri Feb 11, 2011 12:41 am UTC

Why not just put on appropriate safety equipment and pour it into another bottle? It seems like a waste to throw out concentrated acid when it's still perfectly good.

If you must get rid of it, you either need to neutralize it, dilute it, or have someone else dispose of it for you.

Neutralizing it with baking soda will take a huge amount of baking soda and create caustic foam. However, this can be done (it will just take about 33 moles of baking soda, which is 2.75 kg). You probably don't have enough sodium hydroxide on hand to neutralize it with that.

Diluting it is possible. It has to be very dilute before you can safely put it down the drain, so doing this will take a lot of water and a lot of patience.

So the easiest thing to do is to take it to your local hazardous waste disposal facility.
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Re: Safe disposal of sulphuric acid

Postby justaman » Fri Feb 11, 2011 1:05 am UTC

I second taking it to a safe disposal source. However if you must dispose of it yourself, dilute it out carefully in lots and lots of water and remember:

"Do what you oughta, add the acid to the water"
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Re: Safe disposal of sulphuric acid

Postby sikyon » Fri Feb 11, 2011 1:37 am UTC

As someone who has worked with a LOT of 98+% sulfuric acid, I can offer a few suggestions:

Do NOT add base to it directly. It might well explode due to the heat released.

DO add it to water, very slowly. To dilute sulfuric acid safely, you need alot of water. You also need to pour it extremly slowly, depending on the amount of water. Even better: pour it onto ice. Sulfuric acid generates a TON of heat when you mix it with water. If you dump the thing in the water is going to get extremly hot extremly quickly. You need to add the bottle maybe over the course of 15-40 minutes to a bathtub full of water, keep checking the temperature.

On that note, do NOT use a plastic bucket or something to dilute it. The plastic bucket may well deform and collapse under the heat and pressure. I've had pyrex explode because acid was added too fast to the water. Again, adding it to ice is the safest since ice is cold so it can help counter the temperature increase.

After the acid has been diluted to a low concentration you can add alittle bit of base to it at a time to neutralize it. However, you don't have to if you keep diluting it. Highly dilute sulfuric acid is reasonable to dispose of.

Hey, you know what, it's winter. Go use some snow, if it snows where you are. And do it outside! You will get fumes from this process, especially so if want to add base but you will still get fumes just from adding the acid to the water.

If at all possible, dispose in a hazardous waste facility. Always. And don't forget protective gear! Long sleeve clothing, close toed shoes, splash protection (face shield, at least goggles). And don't wear nice clothes, I have holes in various t-shirts that I now wear to the gym because the last button on my lab coat wasn't done up and I leaned against a fume hood.
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Re: Safe disposal of sulphuric acid

Postby letterX » Fri Feb 11, 2011 1:40 am UTC

++$_ wrote:Diluting it is possible. It has to be very dilute before you can safely put it down the drain, so doing this will take a lot of water and a lot of patience.

At some level of dilution it may become safe to pour down the sink. However, at an even greater level of dilution, it becomes a very potent cure for acid-inflicted burns. And you can't very well go pouring valuable cures down the sink, now can you?
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Re: Safe disposal of sulphuric acid

Postby 2.71828183 » Fri Feb 11, 2011 1:48 am UTC

I'd advise against dilution just with water. A strong acid takes a huge amount of water to dilute down to manageable pH (too lazy to calculate, but I seem to remember something on the order of 1000 liters of water to reach a pH of 5 with vaguely similar volumes and concentrations of acid). Baking soda is a fairly cheap base if you buy it in bulk (sold for adjusting pool pH or some such, it comes in bags of about 5kg), and since it's not a strong base, if you use too much you haven't created a hazardous solution to deal with.

I also second the recommendation to put the acid into a safe container and keep it around, if you're likely to do chemistry-type stuff again (or if you have chemically-inclined friends, give it away). 98% sulfuric acid is expensive and relatively hard to obtain. Be sure to label the container correctly and store it safely.

EDIT: I forgot the heat issue. Do as the above poster suggests. I'm more used to HCl, which isn't quite so exothermic when added to water (though adding base still has to be done slowly, and is best done with a slightly dilute mixture instead of the concentrated stuff). Also watch out for acid droplets spattered out from the reaction. A dusting of baking soda (or a washdown with a solution of the stuff) on surrounding surfaces is a good way to get rid of little droplets of acid that you might not have noticed.
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Re: Safe disposal of sulphuric acid

Postby e^iπ+1=0 » Fri Feb 11, 2011 2:06 am UTC

Alright, transferring it to another container sounds like the best solution to me. No reason to get rid of perfectly good H2SO4. What sort of container is suitable?
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Re: Safe disposal of sulphuric acid

Postby Minerva » Fri Feb 11, 2011 6:01 am UTC

Glass is best. I once accidentally dissolved a plastic stirring rod in conc. H2SO4; I assumed that the plastic would be OK... but it ended up dissolving.
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Re: Safe disposal of sulphuric acid

Postby e^iπ+1=0 » Fri Feb 11, 2011 6:28 am UTC

That's what several other sources said, but I figured I'd wait for a confirmation here. So... where might I purchase a largish glass container suitable for storing acid?
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Re: Safe disposal of sulphuric acid

Postby idobox » Fri Feb 11, 2011 10:41 am UTC

I'm proabably going to say something stupid, but wouldn't it possible to use it to disolve scrap metal once it is a little dissolved?
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Re: Safe disposal of sulphuric acid

Postby HungryHobo » Fri Feb 11, 2011 10:53 am UTC

terrible:
load it into a catapult and launch it towards the nearest population centre.

not so great:
find somewhere with lots of chalk/limestone and carefully pour it into a deep crack in the groud.

real:
for serious answers: ya transfering it into another bottle seems best.

Even better:
come up with some cool project to do with it.
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Re: Safe disposal of sulphuric acid

Postby p1t1o » Fri Feb 11, 2011 11:02 am UTC

idobox wrote:I'm proabably going to say something stupid, but wouldn't it possible to use it to disolve scrap metal once it is a little dissolved?


Just now I was thinking of this as a method of disposal - put the acid in a suitable container, add a bunch of scrap metal (iron or steel I guess) and leave in a well ventilated place for a while as hydrogen will evolve, then you'll be left with a iron/copper/etc sulphate solution.

Probably best to dilute the acid to several litres with water first, just to make the whole thing a bit more managable.
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Re: Safe disposal of sulphuric acid

Postby MarvinM » Fri Feb 11, 2011 7:22 pm UTC

If you want to get rid of it then pouring it down the drain is an option, it's sold as a drain cleaner in UK and US. Taking it to a place that disposes of lead acid batteries is another option e.g. your local recycling center.

If you want to keep it in another bottle make sure the stopper is also acid proof and air tight. If the seal is not good the acid will slowly draw water out of the air to the extent containers will over flow. Unless the original container is visibly degrading (brittle, breaking etc) I would be more inclined to trust that even if it is deformed/discoloured, you can always put it inside another container in case it ruptures during further storage.

If your acid is 'good' white/clear you could always buy a bottle of the brown drain grade material and keep your good acid in that bottle depending on the relative cost.
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Re: Safe disposal of sulphuric acid

Postby e^iπ+1=0 » Sat Feb 12, 2011 4:22 am UTC

Found a glass reagent bottle with ground glass stopper for pretty cheap, went ahead and bought it. Thanks, guys.
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Re: Safe disposal of sulphuric acid

Postby Djehutynakht » Sat Feb 12, 2011 4:49 am UTC

Coincidentally I was just about to order some Sulphuric Acid, and this helped for when the time comes. Danke.
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Re: Safe disposal of sulphuric acid

Postby Carnildo » Sat Feb 12, 2011 6:54 am UTC

MarvinM wrote:If you want to get rid of it then pouring it down the drain is an option, it's sold as a drain cleaner in UK and US.

Somehow, I seriously doubt that you can buy 98% sulphuric acid as a drain cleaner.
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Re: Safe disposal of sulphuric acid

Postby minno » Sat Feb 12, 2011 11:47 pm UTC

Carnildo wrote:
MarvinM wrote:If you want to get rid of it then pouring it down the drain is an option, it's sold as a drain cleaner in UK and US.

Somehow, I seriously doubt that you can buy 98% sulphuric acid as a drain cleaner.


Well, your drain can't be dirty if it doesn't exist anymore.
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Re: Safe disposal of sulphuric acid

Postby Minerva » Sun Feb 13, 2011 1:35 pm UTC

Carnildo wrote:
MarvinM wrote:If you want to get rid of it then pouring it down the drain is an option, it's sold as a drain cleaner in UK and US.

Somehow, I seriously doubt that you can buy 98% sulphuric acid as a drain cleaner.


Yes, you certainly can.

http://www.staplesdisposables.com/produ ... in_cleaner

http://www.hectorshardware.biz/shop/pro ... sku=451353

It's the most commonly cited source of easy-to-purchase conc. H2SO4 for home chemistry experiments etc. (and meth labs.)
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Re: Safe disposal of sulphuric acid

Postby jaap » Sun Feb 13, 2011 2:45 pm UTC

Minerva wrote:
Carnildo wrote:Somehow, I seriously doubt that you can buy 98% sulphuric acid as a drain cleaner.

Yes, you certainly can.
http://www.staplesdisposables.com/produ ... in_cleaner
http://www.hectorshardware.biz/shop/pro ... sku=451353
It's the most commonly cited source of easy-to-purchase conc. H2SO4 for home chemistry experiments etc. (and meth labs.)

Those are not 98% though. Possibly around 80%.
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Re: Safe disposal of sulphuric acid

Postby Charlie! » Sun Feb 13, 2011 6:28 pm UTC

The MSDS says " Sulphuric Acid 96%"

So... wow.
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Re: Safe disposal of sulphuric acid

Postby Seraph » Sun Feb 13, 2011 6:37 pm UTC

jaap wrote:
Minerva wrote:
Carnildo wrote:Somehow, I seriously doubt that you can buy 98% sulphuric acid as a drain cleaner.

Yes, you certainly can.
http://www.staplesdisposables.com/produ ... in_cleaner
http://www.hectorshardware.biz/shop/pro ... sku=451353
It's the most commonly cited source of easy-to-purchase conc. H2SO4 for home chemistry experiments etc. (and meth labs.)

Those are not 98% though. Possibly around 80%.

It's a lot closer to 98% then it is to 80%. From the MSDS from the staples link "Description Red coloured acid drain cleaner containing 90-96% sulphuric acid".
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Re: Safe disposal of sulphuric acid

Postby meat.paste » Mon Feb 14, 2011 6:31 pm UTC

A smidge off topic, but you can buy 30% H2O2 solutions at a pool supply store. That surprised the hell out of me.
Huh? What?
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