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Author: Subject: Purification of drain-cleaner acid
JacobM
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[*] posted on 25-1-2022 at 17:56
Purification of drain-cleaner acid


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]
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Rainwater
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[*] posted on 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.




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[*] posted on 26-1-2022 at 04:17


Quote: Originally posted by Rainwater  
I
I believe the brown has emzine inhibitors,

Pardon?
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Sulaiman
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[*] posted on 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.




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AngelEyes
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[*] posted on 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.




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Amos
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[*] posted on 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.

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Rainwater
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[*] posted on 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.




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[*] posted on 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?
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[*] posted on 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)




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[*] posted on 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.
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