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Author: Subject: I will now be building and testing my new Batparatus!
ave369
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[*] posted on 3-12-2015 at 05:52
I will now be building and testing my new Batparatus!


What is the Batparatus? It is a distilling setup for sulfuric acid. If it works, it will be the final solution to the question of Boiling the Bat and obtaining concentrated sulfuric acid. Here is a picture:

apparatus.png - 77kB

Explaining the Batparatus. Before it is used, the Bat is boiled dovn in a common round-bottom flask, until the vhite mist and unpleasant couffing appear. Zen zis raw acid is put in the Batparatus.

It consists of a retort, the upper part of vhich is insulated by an asbestos cord, and a Liebig condenser. Normally you vould not vant to allov sulfuric acid vapors in a vater-cooled Liebig condenser, but ze nose of ze retort and ze antechamber of ze consenser form ze air-cooling span, ze vapors cool down when going through it and are safe now for entering ze Liebig condenser. Zen zey condense. And the asbestos is to prevent refluxing of acid. All my previous attempts to distill sulfuric acid ended in all refluxing and no distillation.

Forgive me my Ubervaldian accent, but nov I'm in a true mad-sciencey mood! Probably that depression swinged to mania.

[Edited on 3-12-2015 by ave369]

[Edited on 3-12-2015 by ave369]




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[*] posted on 3-12-2015 at 06:37


This looks great in concept, and I have never had to concentrate sulfuric...however, boiling the final percentage of water is going to be nearly impossible considering it's so hygroscopic, I doubt it could become much more concentrated that 70% by boiling alone. I may be wrong, but I believe that I have heard that chromium trioxide can be used to dehydrate the acid further.

[Edited on 12-3-2015 by Detonationology]




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ave369
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[*] posted on 3-12-2015 at 06:50


It stops at 70% when simply boiling down. This is what I call a raw acid. And this raw acid I put in a specifically made distilling apparatus.

The chromium trioxide thing is called Zintl-Karyakin distillation. A good thing to do, if you have pure CrO3 or a dichromate of something other than ammonium. That damned ammonium! It reduces hexavalent chromium right when I boil it, and all I get is dirty, green mix of H2SO4, Cr2(SO4)3 and Cr2O3! I even tried isolating pure CrO3 from ammonium dichromate, but some trace of that damn ammonium snooped into my flask and once again made it all green!

[Edited on 3-12-2015 by ave369]




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[*] posted on 3-12-2015 at 06:55


~98% H2SO4 is obtained by the gradual heating of dilute acid to ~300°C!

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[*] posted on 3-12-2015 at 07:09


Quote: Originally posted by hissingnoise  
~98% H2SO4 is obtained by the gradual heating of dilute acid to ~300°C!



Heating to ~300°C will make 85% sulphuric acid at best. You need to actually distill it for it to reach the azeotrope of 98%.
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[*] posted on 3-12-2015 at 07:38


Quote: Originally posted by Deathunter88  


Heating to ~300°C will make 85% sulphuric acid at best. You need to actually distill it for it to reach the azeotrope of 98%.


Well, that is exactly what I'm trying to do. Invented even a new type of distiller to pre-cool the sulfuric acid vapors and prevent thermal cracking in the liebig!

Right now, the distiller is working, the distillate drops merrily, but it is so far mostly water. The asbesting of the retort helped very much, it sped up the distillation and stopped the unwanted refluxing on the retort walls.

[Edited on 3-12-2015 by ave369]




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[*] posted on 3-12-2015 at 08:34


Quote: Originally posted by ave369  
Quote: Originally posted by Deathunter88  


Heating to ~300°C will make 85% sulphuric acid at best. You need to actually distill it for it to reach the azeotrope of 98%.


Well, that is exactly what I'm trying to do. Invented even a new type of distiller to pre-cool the sulfuric acid vapors and prevent thermal cracking in the liebig!

Right now, the distiller is working, the distillate drops merrily, but it is so far mostly water. The asbesting of the retort helped very much, it sped up the distillation and stopped the unwanted refluxing on the retort walls.

[Edited on 3-12-2015 by ave369]


Why not skip the 2 steps of air cooling then water cooling with a single air condenser?
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[*] posted on 3-12-2015 at 09:25


Ta-dam! I've tested the apparatus and it was a success: I've obtained several drops of 98% azeotropic sulfuric acid from it. But then, my stove overheated and threatened to unsolder. You see, Rekord-1 isn't a good brand of heating mantle.

So far, I've got a consolation prize: a full still bottom of technical grade, murky but nevertheless azeotropic acid!

And a Liebig there is to deal with the Mist. You know that Mist? It emerges from the retort nose unscathed, when you inhale it you cough and it smells like Hell. Liebig stops it right there in its tracks.

[Edited on 3-12-2015 by ave369]




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[*] posted on 3-12-2015 at 10:06


Good work! I don't need to do this as I can buy 96% acid, but I recognize the technical challenges you had to overcome.

In some synthesis I was doing drops of water were falling back into the hot H2SO4 due to refluxing - the reaction was violent and scary. Apparently you have eliminated this with the insulation.

I'm surprised that the Liebig condenser has eliminated the mist of oleum/SO3. This can be very difficult to condense.




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[*] posted on 3-12-2015 at 11:34


Wouldn't that be easier to eliminate with a scrap of tyvek and a splash head?
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[*] posted on 3-12-2015 at 12:59


Quote:
Heating to ~300°C will make 85% sulphuric acid at best. You need to actually distill it for it to reach the azeotrope of 98%.

(sigh!)The H2SO4 azeotrope (constant boiling mixture), if it can be called that, appears just below its BP, at which temp. some acid decomposition occurs to keep the water content @ ~2%!
Allowing the acid to cool outdoors or in moist air generally will, of course, lower the conc. slightly as water is absorbed fairly avidly below 100°C.

And simply distilling 85% acid will give 85% acid as distillate . . .

Distilling H2SO4 is useful only when non-volatile contaminents are present!

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[*] posted on 3-12-2015 at 16:25


Quote: Originally posted by hissingnoise  
Quote:
Heating to ~300°C will make 85% sulphuric acid at best. You need to actually distill it for it to reach the azeotrope of 98%.

(sigh!)The H2SO4 azeotrope (constant boiling mixture), if it can be called that, appears just below its BP, at which temp. some acid decomposition occurs to keep the water content @ ~2%!
Allowing the acid to cool outdoors or in moist air generally will, of course, lower the conc. slightly as water is absorbed fairly avidly below 100°C.

And simply distilling 85% acid will give 85% acid as distillate . . .

Distilling H2SO4 is useful only when non-volatile contaminents are present!



That is not true, when I distill 500ml of 93% acid the first 50ml or so is just water with a small amount of acid, not enough to even dehydrate tissue, but the concentration increases until the 98% begins to distill.
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[*] posted on 3-12-2015 at 19:50


Quote: Originally posted by Deathunter88  
Quote: Originally posted by hissingnoise  
Quote:
Heating to ~300°C will make 85% sulphuric acid at best. You need to actually distill it for it to reach the azeotrope of 98%.

(sigh!)The H2SO4 azeotrope (constant boiling mixture), if it can be called that, appears just below its BP, at which temp. some acid decomposition occurs to keep the water content @ ~2%!
Allowing the acid to cool outdoors or in moist air generally will, of course, lower the conc. slightly as water is absorbed fairly avidly below 100°C.

And simply distilling 85% acid will give 85% acid as distillate . . .

Distilling H2SO4 is useful only when non-volatile contaminents are present!



That is not true, when I distill 500ml of 93% acid the first 50ml or so is just water with a small amount of acid, not enough to even dehydrate tissue, but the concentration increases until the 98% begins to distill.

...that's because you're not distilling acid, just boiling more water off until you hit the ~98% azeotrope.
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[*] posted on 3-12-2015 at 21:55


Although not at boiling the vapor composition in equilibrium with 95.06% H2SO4 has the following partial pressures, p, according to Perry's Chemical Engineers' Handbook, 4th ed:

Temp: 282°C (boiling temp is between 285 and 290°C)
pH2SO4 = 52.6mmHg
pH2O = 350.2mmHg

This indicates that the mole ratio H2SO4/H2O =52.6 /350.2
= 0.15

Which in turn means that the vapor is (0.15/1.15) x 100% = 13 mole% H2SO4 = 45wt% H2SO4.

The vapor contains H2SO4 during distillation all the way from a pot concentration of 93% to 98% H2SO4.

At a pot concentration of 98% H2SO4 the vapor will contain 98% H2SO4, as this is the azeotrope.



[Edited on 4-12-2015 by Magpie]

[Edited on 4-12-2015 by Magpie]




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[*] posted on 3-12-2015 at 22:22


Quote: Originally posted by Etaoin Shrdlu  
Quote: Originally posted by Deathunter88  
Quote: Originally posted by hissingnoise  
Quote:
Heating to ~300°C will make 85% sulphuric acid at best. You need to actually distill it for it to reach the azeotrope of 98%.

(sigh!)The H2SO4 azeotrope (constant boiling mixture), if it can be called that, appears just below its BP, at which temp. some acid decomposition occurs to keep the water content @ ~2%!
Allowing the acid to cool outdoors or in moist air generally will, of course, lower the conc. slightly as water is absorbed fairly avidly below 100°C.

And simply distilling 85% acid will give 85% acid as distillate . . .

Distilling H2SO4 is useful only when non-volatile contaminents are present!



That is not true, when I distill 500ml of 93% acid the first 50ml or so is just water with a small amount of acid, not enough to even dehydrate tissue, but the concentration increases until the 98% begins to distill.

...that's because you're not distilling acid, just boiling more water off until you hit the ~98% azeotrope.


Is that not what distilling is? The water has a lower boiling point so boils off with a small amount of acid leaving the bulk acid more and more concentrated until it finally reaches the 98% azeotrope and distills over. Just like distilling say vodka to 95% ethanol the concentration of the distillate rises until it reaches 95%.
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[*] posted on 4-12-2015 at 03:02


Actually, when you distill vodka (or rather moonshine, vodka is made on giant fractionating columns), it's the other way round. The concentration of ethanol in the pot lowers, until it's 1-2% (still bottoms). The concentration of ethanol in the distillate also lowers (the first batch, the pervach, is the strongest, but the most contaminated with toxicants like methanol or acetone. Here in Russia only the men with balls bigger than their brains drink pervach. Then goes the golden middle, which is ethanol with concentration gradually lowering from 70% to 40%. Below 40%, feints begin, they are not potable, either.

With sulfuric acid it is all the same, only the light volatile that escapes is the dreck, and the heavy thing that stays in the pot is the desired product.

[Edited on 4-12-2015 by ave369]




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[*] posted on 4-12-2015 at 04:09


Quote: Originally posted by ave369  
Actually, when you distill vodka (or rather moonshine, vodka is made on giant fractionating columns), it's the other way round.
[Edited on 4-12-2015 by ave369]


By vodka I meant 80% pure alcohol. I realise that it is the other way around but nonetheless distilling H2SO4 is still "Distilling" and not "Boiling off some water".
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[*] posted on 4-12-2015 at 05:15


What that means is that you mean you're hopelessly confused by the simple act of distillation . . . ? :D

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[*] posted on 4-12-2015 at 05:50


Stop arguing. I managed to distill H2SO4 in all possible senses of the word. I got several drops of it before my heating device malfunctioned.

And that the rest of my 98% H2SO4 was from the still bottoms, doesn't change anything.

Also, by finally obtaining sulfuric acid of this strength, I gave freedom to my little inner kewl and performed the reactions "black snake" and making manganese heptoxide (I incinerated a cigarette butt in the heptoxide).

Nevertheless, now I have the technology and think true distillation is overkill: if the glassware is clean and the boiling chips are, too, driving off the last water from the Bat in the pot with this apparatus is the more economical option. 98% sulfuric is now finally an OTC preparation for me! So many possibilities!


[Edited on 4-12-2015 by ave369]




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[*] posted on 4-12-2015 at 05:53


Performing a urine extraction mustn't be mistaken for argument . . .

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[*] posted on 4-12-2015 at 07:02


Hi everyone.

Please keep posts civil and directed to the matter at hand, which is apparently processing sulfuric acid to remove excess water... Not vodka. Not urine, (I can sympathize with the proponents of either liquid, but start a new thread for these- Preferably in whimsy)

Many members have boiled down virgin battery electrolyte (or other more or less dilute acid) when needing concentrated sulfuric acid.

If you have personal experience, please do share your density and/or titration results with us- With a good, careful write up of procedures you followed, both in concentration and testing your final product. No assumptions, just the facts.

I have tested output of MY procedure, using a cheap deep fryer as a sand bath to 90% of the height of a 4000ml tall form beeker, starting with virgin battery electrolyte. Density was 1.82, after air cooling the loosely covered beaker for minimal time @ 20% relative humidity to 20*C.

Density measurement was taken at 20*C on a 50ml sample in a 50ml graduate calibrated for that temperature, scale used was accurate to 1mg. BOTTOM of meniscus aligned with graduation.

As I was satisfied that product was at least 90%, I used it as such. Results were in accordance with calculations, so no more formal titration testing was done.



[Edited on 4-12-2015 by Bert]

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[*] posted on 4-12-2015 at 07:10


OK guys, let me get this straight:
ave369 made a device that allows him to make azeotropic 98% acid from battery acid in a 2 step process:
1st step: Battery acid is boiled in a RBF open to the air until white fumes begin to be evolved. Concentration is ~70%.
2nd step: The boiled down acid is added to the device he made which is a basically a retort connected to a liebig so the vapours cool enough in the air cooled section to prevent thermal cracking of the water cooled liebig while at the same time preventing the awful white mist.

My understanding is that he originally planned to heat up the 70% acid to boiling point and distill. At first water with a small amount of acid is condensed and he discards this (or he adds it to another batch of boiling battery acid to 70%) The ratio of acid to water rises until most of the water has been carried over and he begins getting 98% acid as his distillate.

BUT since his stove overheated he only managed to get a few drops of 98% sulphuric acid distillate. However, if the distillate is at 98% concentration, the acid left in the boiling flask should also be 98%. Thus in the end he was left with a few drops of very pure azeotropic acid and a lot of azeotropic acid with some non-volatile contaminant. He seems to be content with this as he stated "now I have the technology and think true distillation is overkill".

hissingnoise said that distilling 85% acid will result in 85% acid. Could he please clarify what he means by this? What I took it to mean is that if you stuck some 85% acid in a flask, hooked it up to a condenser and boiled it, it would be impossible to collect something more concentrated than 85% acid. However, this is not the case because the less volatile component (water) boils off, leaving the boiling flask's contents more and more concentrated until reaching 98%, when it distills over azeotropically. Thus by keeping an eye on things and changing receiving flasks periodically it is totally possible to concentrate 85% acid to 98% acid...

He also said that I had my knowledge of distillation "hopelessly confused". What exactly am I confusing? Copied from the dictionary on what 'distill' means: purify (a liquid) by heating it so that it vaporizes, then cooling and condensing the vapour and collecting the resulting liquid. What ave369's original plan by that definition is a distillation: he heated 70% acid until it vaporised, then he cooled the vapour and collected at first mostly water, then water and acid, and finally azeotropic acid. What am I getting "confused" about?

edit: I did not see Bert's post since I was writing this post, sorry about that. But I feel that getting the science right is still very important.

[Edited on 4-12-2015 by Deathunter88]
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[*] posted on 4-12-2015 at 08:13


And I'm a she, thank you very much. Still waiting patiently for the custom title "Eastern European Lady of Mad Science" I asked Polverone about, which hopefully will resolve the confusion once and for all.

[Edited on 4-12-2015 by ave369]




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[*] posted on 4-12-2015 at 09:33


Here's a link to a vapor-liquid equilibrium (VLE) diagram for the system H2SO4/H2O. See Illustration 1. This shows the vapor concentration over the whole range of distillation.

http://www.qvf.com/qvf-process-systems/mineral-acids/concent...

Here's a better VLE diagram:

http://www.mie.uth.gr/ekp_yliko/SulfuricAcid-Water_VLE_conce...

Attachment: SulfuricAcid-Water_VLE_concentrations.pdf (328kB)
This file has been downloaded 163 times

[Edited on 5-12-2015 by Magpie]




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[*] posted on 4-12-2015 at 11:05


Quote:
He also said that I had my knowledge of distillation "hopelessly confused".

Well, you did seem to believe that distilling was the only route to obtaining concentrated acid which led me to think you'd never reconcentrated dilute acid . . .

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