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Etaoin Shrdlu
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Quote: Originally posted by S.C. Wack  | | If you're producing fumes like that link does, you're not concentrating the acid...as I've said before the fumes seem to be the result of atmospheric
water, like the hot acid wants it so bad that it'll jump right out of the flask for it... |
He is concentrating the acid, it's just that some sulfuric acid comes off along with the water at higher concentrations, there's no sharp divide at
98% purity where sulfuric acid finally obtains a vapor pressure...
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S.C. Wack
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I don't see how one can think that losing SOx is concentrating the acid. It would not surprise me if some other chemical is formed when this is lost.
If done out of contact of air, only water comes off. Move the hot acid to air, the S something comes right out.
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hissingnoise
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| Quote: | | I don't see how one can think that losing SOx is concentrating the acid. |
Negligible SOx is lost in process and it was widely employed by nitration plants in the past . . .
Today's SACs run under reduced pressure but the principle's the same!
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aga
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I'm a total noob, but even to me it seems obvious that if you drive off more Water than SOx then the remaining solution will be stronger : less water
in the mix.
Are the 'fumes' connected with water vapor and SO3 going *pop* bigtime ?
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S.C. Wack
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Did they heat an open vat of sulfuric acid over a fire in the woods? Do it and tell me that negligible amounts are being lost.
You cannot say that more water is being lost if you don't know. I do not say this without having concentrated many gallons of battery acid from
Lowe's. There is a point I stop.
[Edited on 5-5-2014 by S.C. Wack]
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Etaoin Shrdlu
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We do know more water is being lost. The azeotrope is ~98% in water. That is the point at which sulfuric acid starts coming off at the same
rate as water when the solution is boiled. Before that, more water is coming off than sulfuric acid.
http://books.google.com/books?id=Mtth5g59dEIC&pg=PA546&a...
I've never seen this disputed before. I assume from your experience concentrating many gallons of battery acid that you have data which would
demonstrate otherwise?
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S.C. Wack
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The azeotrope has nothing to do with fuming in air, and neither do vapor pressure measurements not involving undried open air. There is a clear point
in the 80's percent where fuming from hot open containers exposed to moist air becomes an issue.
Needless to say, obtaining vapor pressure measurements in such a situation is troublesome.
[Edited on 6-5-2014 by S.C. Wack]
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Etaoin Shrdlu
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We all know azeotropes have nothing to do with fuming. The question is why in the devil you think fuming means more sulfuric acid is coming off the
mixture than water.
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S.C. Wack
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If you tried it, you'd know the extent of the fuming.
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hissingnoise
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| Quote: | Did they heat an open vat of sulfuric acid over a fire in the woods? Do it and tell me that negligible amounts are being lost.
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Indeed they did, though not in the woods . . . ?
Acid was boiled in silicon-iron pots (Pauling process) suspended above a furnace!
Occasional catastrophic failure of the pots due to poor heat-transfer of the alloy led to boiling acid entering the furnace and the method was largely
superseded by the Simonson-Mantius process which could be run under vacuum . . .
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Etaoin Shrdlu
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If you knew yourself, you'd be telling us what said extent was instead of continually repeating an assumption based on visual assessment.
Don't act as though measuring vapor pressures has anything to do with it either. You could demonstrate your point very easily by boiling dilute
sulfuric acid, taking occasional samples, and showing that the pH stops dropping around 80% or whatever your cutoff point was.
Otherwise, theres really no reason to believe you over every reliable reference that says distilling sulfuric acid is a great way to concentrate to
98%, and I quote, "An acid with the same composition and boiling point is obtained when dilute sulfuric acid is distilled, since in this case
the first distillate is almost pure water."
EDIT: You know, since you're just going to bring up the air thing again, the amount of water air can hold at any boiling point of a sulfuric
acid/water solution at atmospheric pressure is staggeringly higher than the amount of water air can hold at any reasonable room temperature.
The effect of your relative humidity should be pretty much zilch unless you're living on Venus.
[Edited on 5-6-2014 by Etaoin Shrdlu]
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aga
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OK. I feel the need t Moderate, seeing as it's going South about now ...
Sulphuric acid can be concentrated by boiling.
The water leaves a lot faster than the SOx at lower temperatures.
When Fumes are seen, *something* has started to happen : water is not the only thing leaving.
Stop boiling about the point that the Heavy Fumes are seen, and that's as good as the concentration will be if judged by eye alone.
H2SO4 probably behaves in a much more complicated way, however, you boil a dilute solution of the acid, and it gets less dilute
: i.e. stronger solution.
Whichever way you cut it, boiling works.
[Edited on 6-5-2014 by aga]
[Edited on 6-5-2014 by aga]
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blogfast25
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Someone here is going to have to bite the bullet and determine experimentally what max. concentration H2SO4 can be obtained with this (atmospheric)
open vessel boiling in of dilute H2SO4 solutions.
My money is on 95 w% or slightly better.
[Edited on 6-5-2014 by blogfast25]
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Zyklon-A
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I've heard 98.3% is the absolute highest possible to reach by boiling, but I bet yields are terrible.
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aga
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Excellent. First Takers.
ZyklonB has $50 on 98.3%
Blogfast25 has $50 on 95%
Place your bets people.
I will be doing the titration, so the result will be pretty much random.
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S.C. Wack
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| Quote: Originally posted by Etaoin Shrdlu |
Otherwise, theres really no reason to believe you over every reliable reference that says distilling sulfuric acid is a great way to concentrate to
98%, and I quote, "An acid with the same composition and boiling point is obtained when dilute sulfuric acid is distilled, since in this case
the first distillate is almost pure water." |
Where did I say anything about distilling? You seem more interested in trolling than in what is actually happening; take your straw man elsewhere.
Sulfuric acid leaves the open flask in a most obvious way, regardless of whether you say it doesn't. The fumes do not come off in a small amount once
a certain temperature is reached. Less fumes are produced when the surface of the acid is less open to the air, it's obvious if you do it. It
is foolish to continue heating at that level of fuming, because those fumes are not water.
| Quote: Originally posted by hissingnoise | Indeed they did, though not in the woods . . . ?
Acid was boiled in silicon-iron pots (Pauling process) suspended above a furnace! |
Have I been talking about this sort of apparatus, or, something like the fuming flask in the link? This is an "open vat"?
Attachment: DE299774C.pdf (192kB)
This file has been downloaded 438 times
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HgDinis25
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S.C. Wack, boiling Sulfuric Acid is effective uo to 70% concentration. Past that, fumes will start forming. However it is completly possible to reach
98% concentration, at 300ºC.
I've never realy seen anyone arguing about this.
Anyway, here's some proof:
http://www.youtube.com/watch?v=okvvD3-DF9U
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blogfast25
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As far as evidence goes, it's fairly weak. The concentration of the obtained acid wasn't measured.
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aga
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Hahahaha
My sulphuric acid gets concentrated by boiling.
Tested by experimentation.
Seems that You all start Fuming at much lower temperatures !
Being a Noob is a Bonus right now : i don't think i Know enough to think i'm Right, to the exclusion of all else.
Watching Experts is certainly amusing.
[Edited on 6-5-2014 by aga]
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HgDinis25
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Actualy, it's more a proof of persona, if you get where I'm going...
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Zyklon-A
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Boiling dilute sulfuric acid to concentrate it is common knowledge, I've never seen anyone argue this either.
That's not proof, he never tested the concentration - it could be water for all anyone knows. (Although I trust Nurdrage.)
| Quote: Originally posted by aga |
Excellent. First Takers.
ZyklonB has $50 on 98.3%
Blogfast25 has $50 on 95%
Place your bets people.
I will be doing the titration, so the result will be pretty much random. |
I'm not putting a penny on your titration setup unless I see it!
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HgDinis25
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Zyklonb, like I said, proof of persona.
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Etaoin Shrdlu
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| Quote: Originally posted by S.C. Wack | | Where did I say anything about distilling? You seem more interested in trolling than in what is actually happening; take your straw man elsewhere.
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I thought it was common knowledge that boiling while collecting the vapors leaves the same result in the flask as boiling without collecting the
vapors. Straw man? Trolling? Are you referring to yourself?
EDIT: Or have we discovered a macroscale uncertainty principle? 
Again, referring to yourself? Everyone so far has readily admitted it does leave the flask.
| Quote: Originally posted by S.C. Wack | | The fumes do not come off in a small amount once a certain temperature is reached. Less fumes are produced when the surface of the acid is less
open to the air, it's obvious if you do it. |
Increasing the area of the interface is not going to affect the dynamics at that interface. Boiling sulfuric acid in a pan versus a long-necked flask
is just going to concentrate it faster, the same vapors should come off unless you're recondensing the sulfuric acid somehow or there's something
really significant and interesting about the way the system is interacting with the atmosphere, that nobody's described yet. Write a paper?
All anyone's saying is that it's definitely possible to concentrate sulfuric acid by boiling (and I'm also saying there's no reason to think it will
jump out of the flask after water vapor to any significant extent, mentally provocative as the thought is).
The last graph here may be of interest. It is the only one of its kind I can locate right now. The vapor concentration of sulfuric acid climbs
significantly between 90-98%.
http://www.akersolutions.com/Documents/PandC/Mining%20and%20...
Aga, my money's on 98%...to that many significant figures.
[Edited on 5-6-2014 by Etaoin Shrdlu]
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blogfast25
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Proof of persona??? Inventing new types of 'evidence' won't get us out of this pickle.
At the end of the day those who make claims of > 95 % (like NR) should back them up with actual evidence. He didn't do that. The sugar dehydration
doesn't prove actual concentration either, only that it must be quite high.
Time allowing, I might have a stab at this...
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Fantasma4500
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boiling point could be checked to confirm that you would be capable of reaching higher temperatures, i recall that 300*C is the target if you want
96-98% H2SO4
what to measure it with -- thats another question..
but i would suggest that the SO3 coming off the boiling H2SO4/water mixture would also drag some water with it at the same time
also a shed is not a real problem, being more than just new to chemistry and attempting to boil it down in a steel pot on a gas flame and fogging up
an 12 room big house -- thats a difference case
nothing is so bad that its not good for something -- im sure most bacterias in that house was wiped away that day, at least surface bacterias
however.. NH4OH solution could be put next to it to remove the SO3 fumes
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