Sciencemadness Discussion Board - Purification of drain-cleaner acid

Purification of drain-cleaner acid

Rando1234 - 25-1-2022 at 17:56

Hey Folks,

My local store sells "Liquid Lighting Virgin Sulfuric Acid Drain Cleaner", which is 93% acid according to its SDS. It's supposedly brown in color, according to the SDS. I have 2 questions, namely:

- I don't want to distill the acid itself, as hot concentrated H2SO4 is a beast. Would just boiling out the water and bringing it from 93 to 98% remove the color also?
- I plan to use it to make aurintricarboxylic acid (after removing the excess water by distillation of course). Will colored impurities hamper the reaction?

Probably noteworthy that I don't have 30% peroxide.

Thanks,
Jacob

[Edited on 26-1-2022 by JacobM]

Rainwater - 25-1-2022 at 18:30

It depends on what has been added, the brand i get from lows is brown and clears up @ 200c without adding anything, the ace brand has a green tent and does not clear up with heading but will clear up after being used in electrolysis.
I believe the brown has emzine inhibitors, and the green is metal contamination.

If you do not want to add H2O2, any nitrate salt will make a good oxidizer.

The distillation of H2SO4 is not something I want to try. If I do hot work, I want a metal apparatus, not glass.

unionised - 26-1-2022 at 04:17

Quote: Originally posted by Rainwater

I
I believe the brown has emzine inhibitors,

Pardon?

Sulaiman - 26-1-2022 at 04:19

I too found that just boiling drain unblocker grade sulphuric acid destroyed the brown colouring,
with a little h2o2 the colour faded at a lower temperature.

Boiling 93% sulphuric to near azeotropic will create a LOT of white choking fumes.
The acid starts to fume sbove about 70% and by 90% the fumes make clouds....
Explosive bumping is to be expected.

Distilling is more hazardous,
Expect and prepare for bumping causing
Hot sulphuric acid and vapour to violently exit your glassware.
But you do get distilled acid, some less than azeotropic early on, but still useful, some near azeotropic, and the most concentrated, but potentially contaminated, left in the boiling pot.
Very little loss/waste.

AngelEyes - 26-1-2022 at 04:39

I also believe the colour can be removed by dripping it through a column of activated charcoal...though I have not personally tested it. That'd be a lot easier / safer than heating it up.

Cheers

Angel.

Amos - 26-1-2022 at 06:21

I've never found the impurities in any sulfuric acid to hamper a reaction. The most common cause of coloration is trace amounts of organic compounds, or a deliberately added dye, and in either case it doesn't represent any meaningful percentage of the product's composition. 93% is probably good enough for almost any organic chemistry reaction apart from very intense sulfonylations that would likely require oleum anyway, so I would probably just use the acid as is. Boiling said acid might concentrate it a bit more but it will take longer than you think, and generate copious amounts of corrosive fog that will contain a lot of the sulfuric acid you wish to keep. If you really must work with crystal clear acid, you could also try heating a small sample to boiling with a bit of 3% peroxide added to it to see if this clears up the contamination, and then apply the same procedure to the whole bottle if it works. Or buy it from Duda Diesel.

Rainwater - 26-1-2022 at 09:14

Quote: Originally posted by unionised

Quote: Originally posted by Rainwater

I
I believe the brown has emzine inhibitors,

Pardon?

Im two lazy to press the, the spell czech button sum times

Enzyme inhibitors.

unionised - 26-1-2022 at 10:02

I wondered about that but... what enzymes would there be in sulphuric acid, and why would you want to inhibit them?

Rainwater - 26-1-2022 at 17:34

It slows the acid's attack on metal so that it can focus on the clog in the line. Some old buildings use cast iron plumbing for sewer lines. Atleast thats what i have read.
Remimber. Use acid on hair and paper. Bace on fog. (fats oils grease)

TLutman - 26-1-2022 at 17:39

You need to remember what the acid is for, namely unclogging plugged plumbing. They contain corrosion inhibitors to prevent eating any plumbing that isn’t plastic.
I’m unsure for what purpose just adding a dye would be.

As for distilling, my first go at it was as described in a few of the previous posts. I figured the problem was water condensate falling back into the boiling flask and flashing to steam. My last time, I used a 75 degree Bent adapter to eliminate any refluxing in the head and used 2 layers of foil to insulate the rbf and head. I also used ceramic filter media from a fish tank filter as boiling stones. It went quite well, with no bumping, belching, clouds of certain death, nothing.
When the acid starts coming over, it is quite evident in the condenser.

ManyInterests - 26-6-2022 at 10:21

I've boiled sulfuric acid many times and maybe I can give some help?

What I did is put 500 ml of drain opener in a 1000 ml boiling flask and add a stirbar. Then I start the stirring as strongly as I can while adding 30+% H2O2 (hydrogen peroxide) to the mixture. I normally add 10 or 15ml at a time (for a total of 50 or 60 ml) and let it react.

You will see some fizzing as the hydrogen peroxide does it's work and forms a dilute Caro's acid (AKA Piranha solution) that will get rid of the organic compounds and inhibitors. I usually give it 15 to 20 minutes per addition of more H2O2 in order to let it have all the time it needs to react correctly. You will see a color change (if it is brown, the color should change to a yellowish tint) and will eventually become crystal clear. Once all H2O2 is added let it work for another 25 minutes or so to make absolutely sure that all inhibitors are gone. Then turn off stirring and retrieve the stirbar (make sure you have a carbonate or bicarbonate solution ready to quench the stirbar and stick to remove all acids). Adding boiling chips/stones to the acid mixture. I always add more than I think is necessary to prevent bumping.

After this take your mantle or hotplate somewhere outside because boiling sulfuric acid is no joke and you don't want to be anywhere near it once you crank up the heat. What I personally do is use a power bar extender to put as much distance between myself and my mantle as possible and give myself control of the power supply from a distance as well. I do it on my balcony, too.

Once all precautions are in effect and your equipment is outside. Turn up the heat to max and let it go. Observe from a distance.

What you're going to see as it heats up is small wisps of white fumes before it starts to boil. If you added enough boiling stones you will see it boil like water, which is exactly what you want it to see. You will see more and more dense white fumes until you finally see large cloud formations within the flask. This is a sign that the azeotrope is being reached. I honestly keep it boiling for a bit more just in case before turning off the heat and letting it cool down as slowly as possible on the mantle.

It will take several hours for it cool down enough for you to be able to touch the flask without burning your hands, and a few hours more before you can safely pour your acid into your reagent bottle.

My method described above produces very clean, and extremely strong acid. I didn't take a specific gravity reading, but I am confident that it is 98% or very close to it. It is a very thick, syrupy like liquid in there that should be good for all things requiring sulfuric acid.

From 500ml of acid, my final yield is usually around 450ml.

woelen - 27-6-2022 at 00:05

Very interesting. This also makes it possible for EU-based members to make highly concentrated acid from the 15% we can buy. First let a lot of water simply evaporate as suggested by other members on the forums, by putting the acid aside. In this way, one can reach 50%, maybe 60%, without using any electricity. Then boil it down to 80% or so and then finally, outside, doing what you describe above. If the 15% acid is clean and colorless, then of course, the step of using H2O2 to clean it is not necessary.

We now see more and more suppliers, selling cheap 15% acid, at prices between 30 and 40 euros per 20 liters of the dilute acid. This makes it affordable to make small quantities of concentrated acid with reasonable effort and risk. But indeed, this MUST be done outside, on a place, where accidental cracking and spilling does not lead to immediate disaster.

[Edited on 27-6-22 by woelen]

ManyInterests - 27-6-2022 at 03:33

Quote: Originally posted by woelen

Very interesting. This also makes it possible for EU-based members to make highly concentrated acid from the 15% we can buy. First let a lot of water simply evaporate as suggested by other members on the forums, by putting the acid aside. In this way, one can reach 50%, maybe 60%, without using any electricity. Then boil it down to 80% or so and then finally, outside, doing what you describe above. If the 15% acid is clean and colorless, then of course, the step of using H2O2 to clean it is not necessary.

We now see more and more suppliers, selling cheap 15% acid, at prices between 30 and 40 euros per 20 liters of the dilute acid. This makes it affordable to make small quantities of concentrated acid with reasonable effort and risk. But indeed, this MUST be done outside, on a place, where accidental cracking and spilling does not lead to immediate disaster.

[Edited on 27-6-22 by woelen]

Yeah, I had an accidental spill of room temp drain cleaner on my mantle and it ruined half my mantle. I should have worked to completely neutralize everything thoroughly and clean anything before turning it on.

Now I need to do repairs to the 1 liter mantle that I have. I did order a 2 liter mantle that should replace it soon anyway.

PirateDocBrown - 27-6-2022 at 12:31

Quote: Originally posted by woelen

Very interesting. This also makes it possible for EU-based members to make highly concentrated acid from the 15% we can buy.
[Edited on 27-6-22 by woelen]

I'm flabbergasted that the EU won't let you buy even 30%, which is what's used to car batteries.

PirateDocBrown - 27-6-2022 at 12:34

Quote: Originally posted by JacobM

Probably noteworthy that I don't have 30% peroxide.

[Edited on 26-1-2022 by JacobM]

If you are in the US, it's not that hard to source 25%+ H2O2 from pool & spa stores. It can be ordered online as well.

ManyInterests - 27-6-2022 at 14:46

Oh I forgot to mention this:

Quote:

Probably noteworthy that I don't have 30% peroxide.

Where I live 30+% peroxide is restricted, and while some places do sell 29%. Those places aren't near me. Here is what I did to make my 30% peroxide.

It is a time consuming process, but I have done it dozens of times as well and it is proven... slowly evaporating water off 3% hydrogen peroxide.

In my 1000ml beaker, I pour 3% hydrogen peroxide right up to the brim (the beaker can hold more than 1000ml, technically) then I heat it to no more than 80C. With a volume of around 1150 ml of Hydrogen peroxide at that temperature, it can take up to 15 hours for it for evaporate to the 60ml point But by that point it should be 30+% hydrogen peroxide.

I have a liter worth of 33.5% peroxide that I got that way... and it only took me two weeks of non-stop evaporation and an unbelievable amount of 3% peroxide. I had to learn every single shop that sold them to find the cheapest ones to buy from!

I wish I could get 1 liter of 29% like some Canadians can, then it would be elementary to evaporate that one down to 30+% (only a few minutes or so) but as it stands if I need H2O2 this is my best case. It's also why I spent so much time making so much of it. I want to make sure I have enough to last me a while.

PirateDocBrown - 28-6-2022 at 11:53

Quote: Originally posted by ManyInterests

Oh I forgot to mention this:

Quote:

Probably noteworthy that I don't have 30% peroxide.

Even hairdressers should be able to get 10%. That surely must be a better starting point.

ManyInterests - 28-6-2022 at 18:44

True. But you need to look at the ingredients. All the stuff that is above 6% in my area had other things besides hydrogen peroxide and water.

I did look at amazon.ca and I did see they sell 473ml bottles of 12% hydrogen peroxide. Perhaps next time I will get a few of those. It would be much faster, obviously.