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Sulaiman
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Boiling HNO3 plus even hotter cooking oil ?
If I were to distill near azeotropic nitric acid from a 2l rbf in a cooking oil bath,
and the rbf broke,
dumping 1l of boiling acid into the even hotter 3l of hot oil,
would there be a violent reaction ?
('rocket fuel' comes to mind)
I've done similar at smaller scale before but I did not give sufficient consideration to this potential hazard.
Is it very hazardous ?
Would it be safer to do multiple batches using my 500ml mantle ?
CAUTION : Hobby Chemist, not Professional or even Amateur
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DavidJR
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Is mineral oil a viable option? I'd expect it to be much less reactive than cooking oil since it's basically just various large alkanes whereas
vegetable oil is fatty acid esters of glycerol.
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fusso
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What about heating smaller batches (a few ml) separately, then try add the hot acid into hot oil, as a safety test?
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Σldritch
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In my limited experience nitric acid is not that reactive but you might get something like this if the oil is on fire or somehow catches fire:
https://www.youtube.com/watch?v=dYfBkTlIhh4
Which i doubt it would but it could still splatter nitric acid everywhere. Maybe use a sand bath.
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Herr Haber
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Instant fire
Somone on the forum recently suffered this incident and posted about it.
It is one of the things I'm worried about when distilling acid. Working with multi Kg of silver at a time I just cant distill acid in small
quantities.
2 fire extinguishers and 1 fire blanket help me feel a bit safer.
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XeonTheMGPony
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yaaaaaaaa this sounds like disaster in every way I can imagine.
Do not use oil!, buy a mantle from Daschem, then you can more effectively contain a critical failure via Bentonite clay.
Same thing when I distill sulfuric acid now as well. this system will minimize secondary damage but you're going to lose the mantle and such but there
will be no massive searing hot fire ball
https://www.ebay.ca/itm/2000ml-500W-Inner-Sleeve-use-for-2-L...
[Edited on 18-1-2019 by XeonTheMGPony]
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Tsjerk
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Why isn't anyone suggesting a sand bath? No new equipment needed, just replace the oil with sand. It will even prevent the hot acid spilling
everywhere as it is nicely absorbed into the sand. Also your heating apparatus is not destroyed.
[Edited on 18-1-2019 by Tsjerk]
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Elemental Phosphorus
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Quote: Originally posted by Tsjerk  | Why isn't anyone suggesting a sand bath? No new equipment needed, just replace the oil with sand. It will even prevent the hot acid spilling
everywhere as it is nicely absorbed into the sand. Also your heating apparatus is not destroyed.
[Edited on 18-1-2019 by Tsjerk] |
I second this, I have distilled concentrated (and fuming) nitric acid a good number of times, and every time I did it was using a sand bath, until
about a year ago when I got a hot plate and just distilled using a Florence flask. Sand takes a while to heat up and cool down, but it is a good safe
method, and sand in a metal pot or container can be heated using one of those single burner portable propane stoves which in my experience deliver a
lot more heat than a hot plate, and they made things go faster for me.
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Sulaiman
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I've used sand, salt, sand+salt as a heating bath for my 10/19 kit and it was slow, since then I've used cooking oil, and recently a diy 500ml mantle.
@Tsjerk : I think that my best option in this case is a sand bath ... thanks
@DavidJR : thanks - for an equally good option
@fusso : I'm wlling to accept that cooking oil is a poor choice - no need to test
@ Σldritch : that is exactly what made me ask this question
@ Herr Haber : the nitric acid is to make silver nitrate
my target is either one or two kg (not yet decided)
... I have two fire extinguishers and a (non-fire-rated) blanket ready
@ XeonTheMGPony : you confirmed my concern/fear
Thank you all
EDIT : @Elemental Phosphorus : thank you for the confirmation
(you must have posted while I was typing the above 
[Edited on 18-1-2019 by Sulaiman]
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greenlight
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I second Xeon the MG Pony, a heating mantle although not as safe as a sand bath takes a much shorter amount of time to reach boiling temperature.
I always use one for distilling just about anything and if you have decent brand glass and inspect it before using you shouldn't have to worry too
much about breakage.
Be good, otherwise be good at it 
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Sulaiman
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So far I have not broken any jointed glassware in use,
(shipping and wasing/drying/storing is where the damage has occured)
so I got a bit complacent with my informal risk assesments 
I would like a 2 litre heating mantle but I'm very low on funds and shall be for quite a while, so the cheaper sandbath option suits me for now.
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chornedsnorkack
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Does nitric acid cause appreciable transesterification of fatty acid glycerides?
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XeonTheMGPony
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| Quote: Originally posted by greenlight | I second Xeon the MG Pony, a heating mantle although not as safe as a sand bath takes a much shorter amount of time to reach boiling temperature.
I always use one for distilling just about anything and if you have decent brand glass and inspect it before using you shouldn't have to worry too
much about breakage. |
and the inverse, it loses heat fast!, sand bath due to thermal capacity will flood the place with nitric vapor, mantle you lose it and makes a mess
but thermal mass is much lower.
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fusso
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What about a "soda" bath? Use Na2CO3 in place of sand, so if the glass breaks the HNO3 is spilled onto the Na2CO3 and quickly neutralized.
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Sulaiman
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| Quote: Originally posted by fusso | | What about a "soda" bath? Use Na2CO3 in place of sand, so if the glass breaks the HNO3 is spilled onto the Na2CO3 and quickly neutralized.
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Nice idea but the fizzing would be extreme and probably splash acid everywhere, also my lab would rapidly fill up with CO2
I have used both oil and sand baths,
and even a mixed sand & salt bath (I ran out of sand so added salt)
I prefer oil to sand as overall I make less mess,
and I feel that the heating is more even.
Luckily (?) I'm not yet fit enough to set up the distillation so I had time to ponder,
under 'normal' conditions I would have used an oil bath by now,
probably oblivious to the lurking potential hazard - or in hospital 
[Edited on 22-1-2019 by Sulaiman]
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DJF90
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How about using some form of aluminium media (pellets/beads) for a heating bath? Its unreactive with conc nitric acid, and thermal conductivity is
higher than sand.
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DavidJR
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| Quote: Originally posted by DJF90 | | How about using some form of aluminium media (pellets/beads) for a heating bath? Its unreactive with conc nitric acid, and thermal conductivity is
higher than sand. |
I looked at doing this but I couldn't find a cheap/convenient source of aluminium pellets to use.
You don't really want perfectly spherical balls because the packing density and overall thermal conductivity including the voids isn't great.
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clearly_not_atara
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If you're working with multiple kilograms of silver, can't you afford to switch to trifluoroacetic acid or methanesulfonic acid or something?
| Quote: | | What about a "soda" bath? Use Na2CO3 in place of sand, so if the glass breaks the HNO3 is spilled onto the Na2CO3 and quickly neutralized.
|
Along the same lines, maybe you could use sulfuric acid as the "bath"? Below 200 C it shouldn't fume too much.
I guess you risk a lot of NOx produced if it breaks but it should be an endothermic (IIRC) process and not an explosion. Overall I call that a plus.
[Edited on 22-1-2019 by clearly_not_atara]
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Sulaiman
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Aqua Regia at 120+ oC ... mmm
D'oh ! ... see below
[Edited on 22-1-2019 by Sulaiman]
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fusso
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Aqua regia isn't made from H2SO4
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fusso
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| Quote: Originally posted by DavidJR | | Quote: Originally posted by DJF90 | | How about using some form of aluminium media (pellets/beads) for a heating bath? Its unreactive with conc nitric acid, and thermal conductivity is
higher than sand. |
I looked at doing this but I couldn't find a cheap/convenient source of aluminium pellets to use.
You don't really want perfectly spherical balls because the packing density and overall thermal conductivity including the voids isn't great.
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What about using an Al heating block?
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Sulaiman
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OOPS ! ... brain fart ... sorry 
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CharlieA
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"If I were to distill near azeotropic nitric acid from a 2l rbf in a cooking oil bath,
and the rbf broke,
dumping 1l of boiling acid into the even hotter 3l of hot oil,
would there be a violent reaction?"
Pretend that you are boiling water to make pasta in a 2L rbf in a cooking oil bath, and the rbf broke, dumping 1L of boiling water into the even
hotter 3L of hot oil, do you think that there would be a violent reaction?
Another scenario: you're making doughnuts in a deep-fat fryer, when a glass of water on the shelf above, falls into the fryer, do you think that there
would be a violent reaction?
I don't mean to be critical or horse...., but I really don't see the point of your original question. I agree with all of the suggestions to use a
heating mantle. I would add also use a polycarbonate shield between me and the apparatus (provided I couldn't operate it remotely from a safe distance
(I would guess 50 feet or so, preferably from the adjacent room. If a seem to be more cowardly than the Cowardly Lion, it is because I am!
Charlie
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Herr Haber
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| Quote: Originally posted by clearly_not_atara |
If you're working with multiple kilograms of silver, can't you afford to switch to trifluoroacetic acid or methanesulfonic acid or something?
[Edited on 22-1-2019 by clearly_not_atara] |
I never thought of using anything other than the traditional nitric acid.
Out of lazyness or just because "the path most travelled" seemed accessible and safe.
I now only have a few Kg of silverware to treat but will have to dissolve the cement again before it can be used for my final purpose.
I will look into that. I know I can get trifluoroacetic acid. Let's see the price now.
Thanks for keeping my mind open.
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Sulaiman
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For me there has been a great point to this discussion,
members here have helped me to decide to use my diy 500ml mantle.
I really wanted to use my 2L RBFs
but I can do multiple smaller batches instead.
I have gone from a note in my book ".... oil bath? or sand?"
to considering the chemical reactivity of bath oil and RBF contents
and finally, crucially, the thermal capacity of the bath (oil or sand).
So,
thank you all for helping me to make the safer choice,
and
I hope that none of us makes a mistake similar to the one that I could easily have made.
Admittedly I should have immediately come to this conclusion by myself,
but I did not so I'm glad that I asked here before proceeding.
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