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Author: Subject: Acquisition of Conc. H2SO4
S.C. Wack
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[*] posted on 26-3-2008 at 17:13


And yet upon heating, the diluted (5 ml made up to 25 ml) Rooto reduces a significant quantity of chromate and permanganate, which similarly diluted technical and straight electrolyte acid (slightly darker orange with dichromate, surprisingly) do not. The diluted Rooto treated with permanganate is colorless.
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[*] posted on 28-3-2008 at 07:35


Quote:
Originally posted by kilowatt
It is brownish, which is not too far from yellowish. I would consider brown a better description. Where would it have picked up such contaminants? It is made in steel equipment and put into a PE or PP bottle.


If the feed gases for SO2 catalyzation are not purified enough the acid ends up having that color. But especially with lead smelters organic compounds from the sulfide ores end up being volatilized and that results in the brown or black acid.

It sounds like regular technical grade acid. Reagent grade is of a higher purity, and colorless. US4010240 describes such a purification technique from an even more impure acid, e.g.:

Quote:


EXAMPLE 1

15.70 kg of a 83.8% sulfuric acid of dark color, to which 1% of nitric acid had been added, and contaminated by 0.75% of C, 0.52% of N (0.032% of this amount in the form of NH 4 + , the remaining part organically linked) and 0.15% of metals in the form of metal salts were concentrated in known manner in a Pauling apparatus made of glass. 0.7 kg of the 96.1% yellow sulfuric acid obtained (12.52 kg) was heated to 330° C in a distillation apparatus made of glass, and subsequently 3.3 kg of the sulfuric acid obtained were added dropwise at 330° C in such a manner that the acid volume in the still is nearly constant. The distillate was composed of a colorless acid having a content of 97.4% of H 2 SO 4 and 0.032% of C and <10 ppm of N. A 86.3% sulfuric acid of greenish color containing 0.04% of C, 2.6% of N and 0.18% of metals in the form of metal sulfates was obtained as residue.
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[*] posted on 29-3-2008 at 16:44


I found a way to clean up my Rooto. What I do is add 400ml of Rooto to 150ml of 35% H202 in a 2000ml beaker.... Do this outside or under a fume hood!!! After the reaction I boil it down to 400ml or less on a hot plate and the acid now "appears" to be clean H2SO4. Looks like corn syrup. My theory is that the organics and the metals oxidize and vaporize away. Anyone care to confirm this?
Thanks!
HTS
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[*] posted on 29-3-2008 at 17:00


I don't think you need that much oxidizer. Is it safe to boil [that much] H2SO4 with H2O2?


Quote:
Brethericks Handbook

Evaporation of mixtures of excess 50% hydrogen peroxide solutions with sulfuric acid (10:1) leads to loud but non-shattering explosions of the peroxomonosulfuric acid formed [1]. A freshly-made mixture of equal volumes of sulfuric acid and 30% hydrogen peroxide, "Piranha Solution" used for cleaning glass frits, exploded violently on storage. Explosions have also been experienced when cleaning frits, when contamination with organic solvent was suspected. The mixture will, in any case, slowly evolve oxygen to pressurise sealed containers [2][3]. Piranha solution also burst its container after addition of nitric acid [4]. A similar mixture, also containing small quantities of lithium sulfate and selenious acid and intended as a digesting agent for soil samples, burst its container after twelve days undisturbed in a refrigerator. Such solutions are best not stored and, if stored, should not be sealed [5].

1. Analytical Methods Committee, Analyst, 1967, 92, 404
2. Dobbs, D. A. et al., Chem. Eng. News, 1990, 68(17), 2
3. Erickson, T. V., Chem. Eng. News, 1990, 68(33), 2
4. Anon., Environment, Safety & Health Bull., 1993,93(2), 1
5. Stuart, R., Internet, 1991
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[*] posted on 29-3-2008 at 18:14


Quote:
Originally posted by Hammerl
I don't think you need that much oxidizer. Is it safe to boil [that much] H2SO4 with H2O2?


Quote:
Brethericks Handbook

Evaporation of mixtures of excess 50% hydrogen peroxide solutions with sulfuric acid (10:1) leads to loud but non-shattering explosions of the peroxomonosulfuric acid formed [1]. A freshly-made mixture of equal volumes of sulfuric acid and 30% hydrogen peroxide, "Piranha Solution" used for cleaning glass frits, exploded violently on storage. Explosions have also been experienced when cleaning frits, when contamination with organic solvent was suspected. The mixture will, in any case, slowly evolve oxygen to pressurise sealed containers [2][3]. Piranha solution also burst its container after addition of nitric acid [4]. A similar mixture, also containing small quantities of lithium sulfate and selenious acid and intended as a digesting agent for soil samples, burst its container after twelve days undisturbed in a refrigerator. Such solutions are best not stored and, if stored, should not be sealed [5].

1. Analytical Methods Committee, Analyst, 1967, 92, 404
2. Dobbs, D. A. et al., Chem. Eng. News, 1990, 68(17), 2
3. Erickson, T. V., Chem. Eng. News, 1990, 68(33), 2
4. Anon., Environment, Safety & Health Bull., 1993,93(2), 1
5. Stuart, R., Internet, 1991


Although the reaction is quite violent when it's first mixed, it's far from 10:1 or 1:1 Especially after boiling it back down. I have stored the preparation for weeks now in a sealed container at room temperature and have never seen a pressure differential.

I did try a 4:1 H2SO4/H2O2 mixture and ended up with a few suspended globules of greyish material in the finished perparation. My guess is it was some sort of metal. The extra 50ml of H2O2 seemed to clear that up too.

[Edited on 29-3-2008 by hightechstuff]
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[*] posted on 30-3-2008 at 03:55


Quote:
Originally posted by hightechstuff Although the reaction is quite violent when it's first mixed, it's far from 10:1 or 1:1 Especially after boiling it back down. I have stored the preparation for weeks now in a sealed container at room temperature and have never seen a pressure differential.

I did try a 4:1 H2SO4/H2O2 mixture and ended up with a few suspended globules of greyish material in the finished perparation. My guess is it was some sort of metal. The extra 50ml of H2O2 seemed to clear that up too.


To see if your acid contains monopersulfuric acid, Thorpe, Vol. 6 p. 553, mentions that this acid liberates iodine immediatley from acidified potassium iodide solution. So, that's one way to test for it.

Look at how little oxidant the patent uses, like 1% nitric acid. Unless the acid is pitch black, you probably won't need much more oxidant than this. 400 ml acid with as little as something like 3 ml H2O2 could do the trick for removing organics.

The metals might be oxidized, but them clearing up is irrelevant to the purity of the acid. Like the method the patent shows, the metals can be for the most part only be removed by separation through distillation. For that you would need the appropriate distillation apparatus such as a retort. But I'm not familiar with Rooto, is it that contaminated?
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[*] posted on 12-4-2008 at 03:27


"I used to be able to find it by the gallon at a local hardware store but it is getting harder to find all the time. I wouldn't count on it being readily available for long."

I went to NAPA yesterday to look for the fabeled 5 gallons (18.9L) of 35% H2SO4. After a few minutes of fruitless searching I decided to ask the clerk. They had it! 5 gallons for $16. If you take out the energy costs of concentrating that much acid it comes out cheaper (usually) than hardware store acid and it is perfectly clear (even when concentrated).

I am going to use propane for concentration so it should only cost $10 or so to concentrate the acid. I am going to buy a retort so I can do a distillation. This should yield an extremely pure product.

I think the total came out to 6L (~1.5g) of 98% acid.

Even with concentration and distillation energy costs factored in this is still, buy far, the cheapest source of decently pure H2SO4 I have ever come across. This is because of HAZMAT fees for anything ordered from a chemical supplier (most won't even ship concentrated H2SO4 to individuals).

I was appalled at how heavy it was! Damn! I wasn't surprised, though, as I know H2SO4 is very dense. Hmmmm... it's about, what? 24kg? It would be interesting to compare the weight of a 5 gallon container of isopropanol (~14.9kg) to a 5g container of 98% H2SO4 (~33kg).

I am going to buy 2 more once I get some extra money. And then some more after that. You can never have too much H2SO4 and I have a feeling that within the next 5 years individuals purchasing H2SO4 will be virtually unheard of. Mark my words.

I have this last question, though. If I am going to distill the acid anyway, would make no difference if I just bought the BLACK hardware store stuff? Technically, if it's just dissolved solids it should make no difference. I just really don't want to dirty the retort with hard-to-remove shit.

[Edited on 4-12-2008 by MagicJigPipe]




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[*] posted on 12-4-2008 at 06:54


Out of interest how much are you able to distill at a time? It sounds like a tiresome and repetitive job, but if the sulphuric acid is as pure as you assume it to be (and I see no reason why it shouldn't be) then it will all be worth it in the end.

Has anyone tried a solvent extraction with the hardware acid to see if the black stuff is extracted into the organic layer? If the black stuff is presumed to be organic (as a few posts have suggested) then maybe a solvent extraction would clear the acid up. If this works then the only contaminents in the acid would be metal salts, and the easiest method I can think of to remove these is distillation (preferably under reduced pressure; I don't like the idea of conc. sulphuric acid at 330C...)
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[*] posted on 12-4-2008 at 09:32


I calculated the BP of sulfuric acid at reduced pressure and even at 50 torr the BP will be about 190*C. Damn, that's still VERY hot. At 15torr (the max for most home chemists) it's about 145*C. That is managable. So, is 190 but it would still be difficult.

Anyway, a retort is perfect for distilling sulfuric acid. No stuck joints, no leaks etc... It would save time and energy to do it with reduced pressure. Although if you used a hydroaspirator without a trap you would probably have to reconcentrate the acid. Does anyone know if a substantial amount of water can "backflow" into the receiver?

Also, has anyone ever "rigged" a retort for reduced pressure?


[Edited on 4-12-2008 by MagicJigPipe]




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[*] posted on 12-4-2008 at 13:10


At school we use aspirators to produce reduced pressure for buchner filtration. Not once have I ever noticed any backflow. I didn't see a check valve anywhere either, so I was either lucky or... well I cant think of another option. But if you think backflow is problem then you could use a trap, possibly filled with anyhydrous CaCl2 to prevent any water vapor from reaching the distilled acid? Not sure about rigging a retort up for reduced pressure. Are ground joints definately out of the question? PTFE tape could be used instead of silicone grease if you dont want to contaminate the acid.
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[*] posted on 12-4-2008 at 13:44


........ Does anyone know if a substantial amount of water can "backflow" into the receiver? ........

You bet, it can fill the whole apparatus. A very dangerous event in this case without a big enough trap.
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[*] posted on 12-4-2008 at 14:00


PTFE starts to decompose above 260C so if you could pull at least 70 torr or so that would be feasible. bio2, I meant water vapor but thanks anyway for the warning. That would be a dangerous scenario that I might have overlooked.



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[*] posted on 12-4-2008 at 14:48


Good luck finding a PTFE vessel that will withstand those conditions.

Usually teflon lined steel or iron pipe is used.
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[*] posted on 12-4-2008 at 15:18


Some PTFE vessels are "stronger" than glass IMO. I'm not sure how weak it gets at high temperatures. though. Have you ever tried to bend a thick piece of PTFE? It's hard as a rock.



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[*] posted on 12-4-2008 at 22:52


Simple distillation, as from a retort, works well up to an acid concentration of about 70 to 75 percent. As the acid concentration goes above that, an increasing percentage of sulfuric acid comes over in the distillate, some degree of fractionation is helpful for concentrations in that range; without it roughly 1/20 to 1/10 of the acid will distill over on the way to the constant boiling acid.

A retort is OK for distilling already concentrated acid, although the #$%^&8z90=\ fill stopper tends to stick for me.

As you are distilling water out of the acid, the vapour pressure of the water in the receiver will be more important than that from the aspirator. When actually distilling concentrated acid, I'd suggest a pair of suckback traps, the one nearest the acid receiver being to catch water droplets that might carry over from the one closer to the pump.

A small scale version of an acid concentrator is basically a fractional distillation rig with a heated column and a second opening in the distillation pot into which superheated air is blown. The dilute acid is slowly run in the top of the column, which should be long, as it descends it heats up and loses water, which distills out. The concentrated acid collects in the distillation pot. There less emptying of the still pot, because it starts nearly empty, just a little dilute acid, and only receives concentrated acid - volume-wise 2/3 or more of the weak acid distills out of the column as water as it is dripped in and descends. Of course, you need to mess around with heating the still pot and column fairly hot, as has already been commented on. The column can have a gradient along it but the top should still be at 120 C or above.

some data resources:

Note that the 'concentration' header is shifted one cell to the left from where it should be.
http://www.epa.gov/tri/TWebHelp/WebHelp/sulfuric_appendix_1....


The section on sulfuric acid in The Mineral Industry by Richard P. Rothwell, available at Google Books, has a good deal of information that can prove useful.
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[*] posted on 12-4-2008 at 23:42


Hey, thanks for the great info! What I intended to do is concentrate the acid as much as possible by boiling either just in an open beaker or at reduced pressure. The beaker method is easy and it's the way I've always done it. Just put it on a tripod with some ceramic/wire screen and heat it with a bunsen burner until it gets close to 340C and/or starts "fuming".

I'll probably stick with that method for concentration and then use the retort to obtain extremely pure acid.

I've always wondered. Since distilled H2SO4 would technically contain no dissolved solids wouldn't it actually be more pure than ACS grade? Which volatile substances (that can distill over with the H2SO4) are usually present in battery acid grade (technical?) H2SO4? If there's none this should be a good way to get better than ACS grade acid (although, not officially).

And at about $50 per gallon it would rival the cost of ACS grade. (that includes energy costs, a very rough estimate)

[Edited on 4-13-2008 by MagicJigPipe]




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[*] posted on 13-4-2008 at 00:53


Look at the BP curve for the H2O-H2SO4 system. By the time you hit 80% there's an appreciable amount of H2SO4 boiling off, which is going to be hard on the surroundings besides wasting acid.

There's carry over of spray and droplets, another reason to use at least a short fractionation column. Some elements form relatively volatile oxides that transfer over. And you get co-distillation, of which steam distillation is a subset; two materials vapourise in proportion to their vapour pressures, so something that would boil at say 500 C has a slight vapour pressure at the BP of H2SO4 and co-distills. This happens when distilling mercury, too, metals with boiling points above 1500 C have been found to co-distill with the mercury.
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[*] posted on 13-4-2008 at 05:02


I'm just wondering how practical and time consuming it would be to distill H2SO4 with a column.

I'd almost rather distill it 2-3 times.

I wonder how effective a splash guard would be against the "mist". Then all you must worry about is the volatile molecules.




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[*] posted on 13-4-2008 at 08:30


Some splash guards are as big as a short column, and being cylindrical are easier to heat; so it depends on what you've got.

Multiple distillations might cut into yield, partially because of the break-up of the acid into SO3+H2O which form a difficult to condense mist in the cooler areas. On top of that you're increasing the energy use, pushing the cost up.
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[*] posted on 15-4-2008 at 07:08


What would be the likely outcome of trying to use electrically generated O3 and nitrogen oxides in place of the burning salpetre to oxidize SO2 over water? Or trying the same oxidization actually in the water?
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[*] posted on 31-8-2008 at 15:54


Quote:
Originally posted by Intergalactic_Captain
Rooto is my brand of choice when it comes to hardware store acid. 92%+ with no detergents, dyes, or other shit...There may be something, though, as it has a yellow tint to it. I use it primarily for nitrations with potassium and ammonium nitrate as the nitric source, and have never had a problem with it. ~$9USD/quart, not sure if it's available overseas.
Ibeen buying Rooto/Nitrate of Soda 15-0-0 (in nice white prills) from ace hardware for some time and the drain cleaner always had a brown dye?So far havent had any issues with it discoloring the end product of my nitrations just curious about the discrepancy?
If i have the time I prefer to order auto battery electrolyte
and reduce it as I havent a clue(other than perhaps residue
of an iron pickling process) what may be in the drain cleaner
and what effect it may have over time with the finished
product, though I believe there are some, but far less impurities in the electrolyte.Unfortunately the MSDS doesnt go into great detail.
With that in mind and unfortunately being a true shadetree
'chemist' I inspect the nitration product daily(kept damp in the fridge) and try to use it within a week. Including fulminate primaries.

[Edited on 31-8-2008 by grndpndr]

[Edited on 31-8-2008 by grndpndr]

[Edited on 31-8-2008 by grndpndr]

[Edited on 31-8-2008 by grndpndr]
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[*] posted on 1-9-2008 at 10:52


For a while I couldn't even find any of the otc drain cleaners here in the USA, but lately I have had no problem getting it (98%)on E-Bay. I of course use it for my bio-diesel. The same for NaOh . Of course you get stuck with that expensive haz-mat fee. Just check out the Bio diesel suppliers on the net.
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