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Author: Subject: Sulfuric acid purification problems
Cathoderay
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[*] posted on 20-11-2023 at 09:51


OK. That type of precipitate is called "flocculent". That could be something organic if you didn't use enough peroxide or cook it long enough.

The MSDS is obviously not accurate. Most of the time info on a MSDS is stated approximately because the exact formula is proprietary (company secret) and the exact
amount of contents are not not important for safety. The sheet would often state something like Sulfuric acid 92 - 94%, Water 6 - 8%. That sheet should state that there is something else there, if the inhibitor is very safe and only there in a very small amount maybe they don't have to include it. Giving a range also makes it easier on the manufacturer because a MSDS is somewhat of a legal document and by giving a range they don't have to guarantee an exact percentage or test for it.

You didn't say how much acid there was that you added the hydrogen peroxide. In chemistry ratios are important. In your original post you said you stopped boiling because the color go dark, why did you do that?

I don't know how much peroxide is enough. Just how pure the sodium carbonate is would be another question. Someone else might have an idea of what that brown stuff is.
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fx-991ex
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[*] posted on 20-11-2023 at 12:44


$$H2SO4 + Na2CO3 \rightarrow Na2SO4 + CO2 + H2O$$
Could the carbonate react with the acid to make sodium sulfate?
I guess the acid was removed completly and replaced with water from the filtering/precipitate, just making sure.

[Edited on 20-11-2023 by fx-991ex]
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Sir_Gawain
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[*] posted on 20-11-2023 at 12:54


Quote: Originally posted by Cathoderay  

You didn't say how much acid there was that you added the hydrogen peroxide. In chemistry ratios are important. In your original post you said you stopped boiling because the color go dark, why did you do that?

The peroxide was added to about 250 mL of sulfuric acid. I'm sorry if I was unclear; I meant it was night time, not that the acid got dark.




“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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Cathoderay
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[*] posted on 21-11-2023 at 09:53


I thought I posted something last night but it isn't here now. I must have clicked the wrong thing.
To figure out what that stuff is it is important to rule out organic inhibitors.
Reading between the lines of this NileRed video, it seems like you added enough peroxide. Maybe you didn't boil it long enough.
https://www.youtube.com/watch?v=4DUGRWjdNLI
Try boiling it some more and maybe added more peroxide.

A flame test is a good idea if there is something like calcium sulfate in it. Don't add anything with sodium beforehand because the bright sodium flame can mask other things.
This Wikipedia link has a good video link in it.
https://en.wikipedia.org/wiki/Flame_test
You may want to neutralize some of the high acidity before doing tests. The best thing would be ammonium hydroxide since that will not add any metals that you might want to test for later.

I wouldn't be surprised if the acid the cleaner was made from was the cheapest they could find, not laboratory grade. It may even have been "once used" by another chemical plant to clean vessels of slight water and contamination. The cleaner manufacturer then added the inhibitor and maybe a little more water. After all the intended use is to remove muck from drain pipes, then into the sewer.

I'm running out of ideas, maybe someone else can add to this.
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Sir_Gawain
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[*] posted on 21-11-2023 at 19:35


I don’t think it’s organic. Over 300*C piranha for 30 minutes probably would destroy any organic material. Next time I concentrate some, I’ll boil it longer.



“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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[*] posted on 22-11-2023 at 01:33


Speaking of, I wonder if anyone has already recycled sulphuric acid used for diethyl ether synthesis. Since the reaction forms water and some other products, but the sulphuric acid being mainly catalytic should remain more or less untouched, it would be nice to be able to recover it. However, barring distillation, I don’t really see how to do it.
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Sir_Gawain
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[*] posted on 22-11-2023 at 04:49


If you use pure ethanol, all the by products should be organic and you can purify it by boiling it down. If you have hydrogen peroxide, add some.



“Alchemy is trying to turn things yellow; chemistry is trying to avoid things turning yellow.” -Tom deP.
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Cathoderay
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[*] posted on 22-11-2023 at 11:23


I noticed in the comments of that NileRed video that someone said they tried the peroxide method with several different brands of drain cleaner. The person said that three were found that did not work with that method. The brands were not listed.

BTW, not to nit-pick (but nit-picking kind of goes along with science), but did you measure the temperature? Didn't you say you simmered it in your original post?
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Sir_Gawain
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[*] posted on 22-11-2023 at 12:43


Judging by the fact that the sulfuric acid was slightly boiling and letting off a huge cloud of acid vapor, I'd say it was around 300 C. The hotplate I used can melt lead, and when it was dark the first time I could actually see it glowing.



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[*] posted on 23-11-2023 at 02:25


I just bought 30% sulpheric from Rileys auto parts, I havent made it to the sulpheric distillation yet but the distillation curve is very wide and I suspect that its going to be very easy to boil off most of the water with only maybe 4 stages of distillation (theoretical stages using rashing rings).

Seems like alot of work to try to use some multi component source, this is a good time to use that water asperator or eductor on the outlet of the condenser?
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[*] posted on 23-11-2023 at 02:28


Quote: Originally posted by Sir_Gawain  
Judging by the fact that the sulfuric acid was slightly boiling and letting off a huge cloud of acid vapor, I'd say it was around 300 C. The hotplate I used can melt lead, and when it was dark the first time I could actually see it glowing.


Do you guys monitor the top and bottom still temps, I built my own top side temp probes and watch on a raspberry pi and my heat source has a display.

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[*] posted on 23-11-2023 at 05:09


The battery acid source is very pure sulfuric acid around %30 consentration
Very expensive to, here it is over $30 per quart.
If your distilling anyway, why not use the cheap drain cleaner?

When consentrating H2SO4, i have found that using a simple distillation is more
than sufficient. Ive never needed to add packing. The water that comes over has
traces of acid, but after distilling a full litter of battery acid, it took less than 0.5g of
baking soda to bring the ph of the distillate over 7. Sulfuric is easy to seperate.

Using a vacuum distillation will lower the boiling temperature, and help with any
leaks in the appratus. Also, adding a thin capillary bubbler will help with bumping.

Take extream safty precautions. Boiling sulfuric acid gives no second chances.
One drop will scar you for life, half a liter will shorten that life so you dont have to
worry about the scars

[Edited on 23-11-2023 by Rainwater]




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[*] posted on 24-11-2023 at 00:43


Quote: Originally posted by Rainwater  
The battery acid source is very pure sulfuric acid around %30 consentration
Very expensive to, here it is over $30 per quart.
If your distilling anyway, why not use the cheap drain cleaner?

When consentrating H2SO4, i have found that using a simple distillation is more
than sufficient. Ive never needed to add packing. The water that comes over has
traces of acid, but after distilling a full litter of battery acid, it took less than 0.5g of
baking soda to bring the ph of the distillate over 7. Sulfuric is easy to seperate.

Using a vacuum distillation will lower the boiling temperature, and help with any
leaks in the appratus. Also, adding a thin capillary bubbler will help with bumping.

Take extream safty precautions. Boiling sulfuric acid gives no second chances.
One drop will scar you for life, half a liter will shorten that life so you dont have to
worry about the scars

[Edited on 23-11-2023 by Rainwater]


Which one is worse 98% sulpheric or 98% nitric?
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Sir_Gawain
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[*] posted on 24-11-2023 at 10:40


Distilling nitric acid is waaaaaay easier! Pure nitric acid has a boiling point lower than water. Even boiling nitric acid is far less dangerous than hot sulfuric.



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Rainwater
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[*] posted on 25-11-2023 at 05:30


Without trying to sound like im belittling the danger factor, nitric acid is easier to distille.
Boiling acid, is just that.
Nothing safe about it, but can be done safely as long as you take proper precautions.

I try to setup my appratus in such a way, if the entire thing shattered and liquids went everywhere,
it only requires me to put the on/off switch into the off position and wait for stuff to cool.
Ive rigged most my stuff to be worked remotely so i can be at a minimum safe distance to make
adjustments.
when things go bad, they go bad way over there, far away form people, places, or
things i care about




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[*] posted on 25-11-2023 at 13:16


Quote: Originally posted by Rainwater  
Without trying to sound like im belittling the danger factor, nitric acid is easier to distille.
Boiling acid, is just that.
Nothing safe about it, but can be done safely as long as you take proper precautions.

I try to setup my appratus in such a way, if the entire thing shattered and liquids went everywhere,
it only requires me to put the on/off switch into the off position and wait for stuff to cool.
Ive rigged most my stuff to be worked remotely so i can be at a minimum safe distance to make
adjustments.
when things go bad, they go bad way over there, far away form people, places, or
things i care about


Thats a good idea, I have a switch panel with each section on a switch but its under the apparatus which I need to move it. I have a blow down fan that blows down the whole room in seconds.

Its probably fair to say that while nitric is "better/easier" you dont want to be breathing in either one. In order to get pure nitric you have to break the azeotrope though. Has anyone ever used molecular sieve to do a final clean up of nitric to get it super pure? I built a rough one at the very end of the condenser on second stage distillation but still a long way from testing it.
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[*] posted on 25-1-2024 at 23:34


Quote: Originally posted by Sir_Gawain  
Distilling sulfuric acid is not something I feel comfortable doing. I’m afraid my condenser’s going to explode.
[Edited on 16-11-2023 by Sir_Gawain]


Try my old condenser saving trick. There should be two condensers: one air-cooled precooler and one water-cooled main condenser. In the precooler, sulfuric acid vapors get precooled to a temperature that is comfortable for the water-cooled condenser. Concentrated vapors condense in the precooler and flow to the main condenser as a liquid.




Smells like ammonia....
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Sir_Gawain
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[*] posted on 26-1-2024 at 12:09


If I had a good quality Pyrex condenser I would try it, but I only have a cheap Chinese one. Tom from Extractions&Ire distilled sulfuric acid using a similar condenser, air cooled, and it still broke. I haven't ran into any purity problems with my sulfuric acid yet, so I don't think distillation is worth the risk.



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