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ave369
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A safer procedure of mineral acid synthesis
This post is mostly addressed towards beginners, not experienced independent chemists who already know all that.
Everyone knows that all mineral acids start with sulfuric acid. Everyone knows that the more concentrated the acid is, the better. Everyone also knows
that concentrated sulfuric acid is made by boiling battery acid.
However, what also many people know is that highly concentrated sulfuric acid has a boiling point above 300 degrees C. This is already enough to ruin
some glassware by thermal cracking, and more than enough to burn holes through hapless independent chemists that happened to be nearby.
It is generally safe to concentrate battery acid up to 70-80%, until the white mist appears (the temperature here is around 200 C, which is easier for
glassware to handle). And here is the idea: stop here! Do not boil any more! There is a better method to get conc. sulfuric acid and even oleum, and
you will also receive nitric and hydrochloric acids as a nice bonus!
The idea is to use the "tower grade" sulfuric acid that was boiled until the mist appears for Glauber's classic mineral acid syntheses. This
concentration is enough to get both azeotropic nitric and fuming hydrochloric acids. And the side products...
Ta-dam! They are bisulfates!
These bisulfates can be used to convert your leftover tower sulfuric acid to oleum. Calcine the bisulfates to convert them to pyrosulfates. These
pyrosulfates you put into your worst test tube, the one which it won't be a shame to lose, stopper the tube with a PTFE stopper with a Gamma-shaped
glass tube, with the glass tube's other end in a flask with 80% sulfuric acid, and...
FFFFFF--IIIIII--RRRRRR-EEEEEE! at the test tube. The pyrosulfate releases sulfur trioxide which goes into your tower acid and converts it to oleum.
There is no need to boil the acid itself.
What's next? You've got tower sulfuric acid, oleum, azeotropic nitric acid and fuming hydrochloric acid. You now have to make 98% sulfuric and red
fuming nitric.
To make 98% sulfuric, carefully dilute oleum with 70% sulfuric until the oleum no longer fumes.
To make RFNA re-run your Glauber's nitric acid synthesis with 98% sulfuric.
Smells like ammonia....
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aga
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Wow !
Just Wow.
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papaya
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I like how you describe the process Ave, of course it will be more complex than presented, and as you are an russian, I think you've already seen this
before: http://chemistry-chemists.com/N1_2009/ChemistryAndChemists_1...
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Metacelsus
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In my view, making oleum won't be a "safer procedure." However, the other ideas (only concentrating acid to 80%, etc.) are good. In fact, my stock of
sodium bisulfate comes from nitric acid synthesis, and I can personally say that the method works quite well.
Of course, here in the USA I can just buy 98% sulfuric and 31% hydrochloric acids as cleaning products. (In the same country that restricts iodine!)
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byko3y
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I described a good procedure for concentration and distillation of sulfuric acid up to 92-96% in an appropriate thread about sulfuric acid. Also
there's thread about preparation of oleum from bisulfates and pyrosulfates.
http://chemistry-chemists.com/N1_2009/ChemistryAndChemists_1... - this one is actually a translation of procedure made by len1 in his book
"Small-Scale Synthesis of Laboratory Reagents with Reaction Modeling"
Cheddite Cheese, it's not that big problem once you actually know how to dehydrate sulfuric and hydrochloric acid, which is actually a really easy
process (HCl can be concentrated with CaCl2). But also I realize I've missed the time when a lot of reagents like acetone, sulfuric, hydrochloric
acid, phosphorus were perfectly legal. So I try to catch up for the lost time.
Good news are: the guys who became accustomed to usage of nowadays banned reagents, today they have the same problems as me 
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ave369
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byko3y, phosphorus is no longer in the FSKN lists. AntrazoXrom sells it by mail order with no fuss. Technical grade acetone is everywhere in the
hardware stores of my town.
Smells like ammonia....
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byko3y
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So sad I don't live in russia. No phosphorus and acetone here. Well, except matches and nail polish remover.
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kecskesajt
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Niiiiceee. What about the thermal decomposition of Fe or Cu sulphates?Much cheaper for me.
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byko3y
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Iron sulfate decomposition is a relatively expensive process because you need to heat the compound to red glow. Either porcelain retort or quartz
vessel needed for that. And a furnace, of course.
[Edited on 31-8-2015 by byko3y]
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ave369
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As far as I know, copper sulfate has the same rate of decomposition and the same required temperatures as sodium bisulfate. But sodium bisulfate you
get for free as a side product, and blue vitriol you have to buy in the gardening store.
Smells like ammonia....
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aga
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(acetone was replaced with ethyl acetate in NPR years ago)
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ave369
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Forgot to add an important caveat for the main text: to get bisulfate, pour sulfuric acid in excess. This morning I've forgot about it and poured too
little acid when making HCl. The resulting cake in my retort wasn't NaHSO4, it was a crazy mixture of NaHSO4, Na2SO4, unreacted NaCl, and to boot NaI
and elemental iodine (the salt was iodinated. Damn health nuts!)
Smells like ammonia....
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aga
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How much excess sulphuric acid ?
Сколько еще, и кто пил всю свою бензин?
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ave369
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As my experience tells me, in a 250ml retort the proper amount of 70-80% sulfuric acid is a layer the thickness of my pinky finger above the layer of
the acid-permeated salt.
And it's not "кто пил всю свою бензин", it's "кто выпил весь свой бензин". And thank you very much, we do not
drink hydrocarbons. Medical grade ethanol, yes. Gasoline (or Coleman fuel, or naphtha, or even maybe pet ether, they are all бензин), thank you
very much but no.
[Edited on 1-9-2015 by ave369]
Smells like ammonia....
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papaya
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I fear to comment  I know only about pinky noses after vodka, not gasoline!
[Edited on 1-9-2015 by papaya]
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Marvin
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I've read that oleum can be made by dissolving the pyrosulphate in ordinary concentrated acid and cooling to precipitate the neutral sulphate. Might
be a lot easier than heating the pyrosulphate, what sort of temperature is needed for that?
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ave369
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I'll try to do this, if nobody refutes this method. I've just got a royal yield of bisulfate while making fuming HCl, when I dry and calcine it, I'll
check.
[Edited on 1-9-2015 by ave369]
Smells like ammonia....
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aga
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It sounds like a great experiment.
Please take photos.
We like photos of the outside world.
[Edited on 1-9-2015 by aga]
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Camroc37
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Good thing China doesn't really care; Dollar-store nail polish remover still has it!
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j_sum1
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Let's see if I have this right.
I have easy OTC access to sodium bisulfate. I have some H2SO4 that I made by myself via electrolysis. So, with these, I can produce as much H2SO4 as
I want -- for the price of a little bit of sacrificial glassware. (I break stuff anyway!)
Produce SO3. Concentrate half my acid to oleum. Dilute back with the remaining acid to get high conc sulfuric. Dilute further by adding to water.
Lather, rinse repeat.
Is that right?
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ave369
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j_sum, if you have an unlimited supply of dilute sulfuric acid, then yes, you can concentrate it in large amounts. That's what I'm doing now: buying
cheap battery acid in a spare car parts shop and making real, hardcore sulfuric acid from it. Getting other mineral acids by the way (I don't have
access to OTC bisulfate, so I have to make my own from chlorides and nitrates).
However, it's the "heating the pyrosulfate" bit that requires sacrificial glassware. So you should only rely on it for the last step: from 80%
sulfuric acid to over 100%. If you try to SO3-nate dilute sulfuric acid without boiling it down first, you will need too much sacrificial glassware.
You will end up sacrificing your entire lab. Liters of boiled down battery acid should be the main source of H2SO4 in my method, and the decomposition
of pyrosulfate just the final kicker to increase the oomph of the product. Just to replace boiling down over 80% and producing Cytherean clouds of
that same SO3 in your kitchen.
So you don't buy tons of NaHSO4, calcine and decompose it to turn your one liter of dilute H2SO4 to oleum. Kicking the required SO3 out of "tons" of
NaHSO4 requires more than just sacrificial test tubes, maybe a big retort made of platinum-unobtainium alloy, and those kilograms of SO3 are insanely
dangerous themselves. If you want to follow my method, you take your electrolysis machine, make more liters of dilute acid, boil it down to produce
maybe 200 grams of tower grade acid, and then fire at the pyrosulfate in the sacrificial test tubes.
[Edited on 2-9-2015 by ave369]
Smells like ammonia....
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kecskesajt
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Here,battery acid is more expensie than cc. H2SO4. And be aware that battery acid contains a lot of lead.
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careysub
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Quote: Originally posted by ave369  | | Just to replace boiling down over 80% and producing Cytherean clouds of that same SO3 in your kitchen. |
"Cytherean" - I like it!
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ave369
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Here in old Mother Russia it isn't. And brand new, rather than used, battery acid here has no contaminants.
Smells like ammonia....
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careysub
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If doing this on a substantial scale (test tubes are pretty cheap, flasks - not so much) I would think using iron pipe as the sacrificial reaction
vessel might be a good idea. Drill a hole in the cap, and run in stainless steel tubing (you might need to torch heat the tubing to keep the SO3
flowing).
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