VeritasC&E
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What yields when preparing Nitric Acid from Salts?
What yields are you guys getting when preparing nitric acid from salts through different methods?
e.g. Ca/Na/K...NO3 + H2SO4/H3PO4/C2H2O4
Which one(s) do you recommend?
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B(a)P
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I use KNO3 / H2SO4 and typically get yields of around 60% based on sulfuric acid. Go slow with your heating to give
you the best yields.
Also check out this thread http://www.sciencemadness.org/talk/viewthread.php?tid=13749
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VeritasC&E
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Thank you for this information!
I read through the thread: It's mainly focused on trying to get high % HNO3 rather than high yields. It contains some good tips. Different methods are
mentionned but yields of each aren't discussed.
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PirateDocBrown
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I use NaNO3 and NaHSO4, both really cheap. KNO3 would be fine, also. I use an excess of the bisulfate, and get 80% + yields. Slow and low heat.
I do it notionally "dry", but in fact add whatever dilute HNO3 I have laying around, to bring up concentration. NO2 waste gas gets led though 28%
H2O2, to make more dilute acid as I go.
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Tsjerk
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More water - higher yield. When you are talking about yield, what is your limiting reagent? Details are important when discussing this topic.
I didn't want to respond in this topic at first as I thought it looked like a low effort spoon-feeding question. Why don't you give more details in
your first post?
[Edited on 15-8-2022 by Tsjerk]
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B(a)P
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I assumed you wanted fuming nitric acid. After rereading your post I am guessing that you want the most nitric acid for the least cost?
If I am making azeotropic nitric acid I use the same reagents, but partially dissolve the potassium nitrate in half of its mass of water. Yields are
then more like 75% based on sulfuric acid.
I would also add that I end up making a small amount of dilute nitric acid by capturing the produced NO2 when making fuming nitric acid (I
have never calculated my total yield including the dilute portion). I find I generate almost no NO2 when making azeotropic nitric acid.
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woelen
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My best yields indeed are when I add a little water to the sulfuric acid / NaNO3 mix. WIth the water you get nice clean acid, without the water, quite
a lot of NO2 is produced and you get yellow/orange acid. Boiling temperature with added water is higher (well above 100 C), while the dry mix boils
well below 100 C.
Cheapest acid most likely can be made by mixing NaNO3 (or KNO3) and NaHSO4.H2O (the commercial pH-minus for swimming pools). This NaHSO4.H2O melts in
its own water of crystallization and this gives some water in the mix, which with the NaNO3 gives moderately concentrated acid. The disadvantage of
using NaHSO4.H2O is that more solid stuff remains behind, whuch can form a nasty hard cake in the flask and may require stronger heating, with more
risk of cracking the flask. I have no personal experience with the use of NaHSO4.H2O, but I have read about it (don't remember where anymore, maybe on
sciencemadness?).
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VeritasC&E
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Quote: Originally posted by PirateDocBrown  | I use NaNO3 and NaHSO4, both really cheap. KNO3 would be fine, also. I use an excess of the bisulfate, and get 80% + yields. Slow and low heat.
I do it notionally "dry", but in fact add whatever dilute HNO3 I have laying around, to bring up concentration. NO2 waste gas gets led though 28%
H2O2, to make more dilute acid as I go. |
That's a good yield!
How much do you think you would get without using any H2O2?
Do you have any feedback regarding the challenges related to caking mentionned by Woelen?
"The disadvantage of using NaHSO4.H2O is that more solid stuff remains behind, whuch can form a nasty hard cake in the flask and may require stronger
heating."
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VeritasC&E
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| Quote: Originally posted by Tsjerk | More water - higher yield. When you are talking about yield, what is your limiting reagent? Details are important when discussing this topic.
[Edited on 15-8-2022 by Tsjerk] |
I had stochiometric amounts in mind but when using an excess of either reagent the yield can be given as a dual value relative to each (e.g. "Yield of
product was 55% (r.t. H2SO4) / 61% (r.t. KNO3).
How much difference in yield do you think it makes to target azeotropic HNO3 (or even >50% HNO3) vs 95%? Is the loss mostly from fume losses or
from remnants in the still?
[Edited on 16-8-2022 by VeritasC&E]
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VeritasC&E
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| Quote: Originally posted by B(a)P | I assumed you wanted fuming nitric acid. After rereading your post I am guessing that you want the most nitric acid for the least cost?
If I am making azeotropic nitric acid I use the same reagents, but partially dissolve the potassium nitrate in half of its mass of water. Yields are
then more like 75% based on sulfuric acid.
I would also add that I end up making a small amount of dilute nitric acid by capturing the produced NO2 when making fuming nitric acid (I
have never calculated my total yield including the dilute portion). I find I generate almost no NO2 when making azeotropic nitric acid.
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Yes, that's correct!
The topic is intended to compare methods of producing HNO3 with a particular (but not exclusive) focus on making the most nitric acid for the least
cost (as long as the product is at least >50% HNO3 to exclude myriads of less practical / more exotic routes).
I personally never use huge amounts of very high % HNO3, and whenever I need such high % reagent of a hygroscopic/problematic reagent I find it best
to prepare/dry the portion I'll need before use.
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VeritasC&E
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| Quote: Originally posted by woelen | My best yields indeed are when I add a little water to the sulfuric acid / NaNO3 mix. WIth the water you get nice clean acid, without the water, quite
a lot of NO2 is produced and you get yellow/orange acid. Boiling temperature with added water is higher (well above 100 C), while the dry mix boils
well below 100 C.
Cheapest acid most likely can be made by mixing NaNO3 (or KNO3) and NaHSO4.H2O (the commercial pH-minus for swimming pools). This NaHSO4.H2O melts in
its own water of crystallization and this gives some water in the mix, which with the NaNO3 gives moderately concentrated acid. The disadvantage of
using NaHSO4.H2O is that more solid stuff remains behind, whuch can form a nasty hard cake in the flask and may require stronger heating, with more
risk of cracking the flask. I have no personal experience with the use of NaHSO4.H2O, but I have read about it (don't remember where anymore, maybe on
sciencemadness?). |
Thanks for these informations!
Do you think there is any advantage (in terms of maximizing final yield) in first producing more dilute nitric acid (only as dilute as necessary to
maximize final yield) and drying that in a second step using H2SO4? Or would that just compound the losses? (it probably would cost a bit more in
terms of H2SO4)
[Edited on 16-8-2022 by VeritasC&E]
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woelen
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What is best for you depends on many things. Is the H2SO4 the cost-determining or hardest to get reagent, or is it the nitrate salt? How much time do
you want to spend on the process? How much do you make in one batch?
My first guess would be that if you really need fuming (nearly anhydrous) acid, then just make it in one go. Concentrating more dilute acid with H2SO4
and distilling it off will also lead to decomposition. It is just, that the azeotrope is much more stable than the pure acid. Pure HNO3 slowly
decomposes, with formation of NO2, H2O and O2. At its boiling point this effect is quite strong. The azeotrope, which is a mix of HNO3 and H2O does
hardly suffer from that and it can be boiled hardly without decomposition.
If you prepare the fuming acid, then keep in mind that storing this is a pain in the ass. It eats nearly every cap you can imagine, and it cannot be
safely ampouled, because it slowly builds up pressure, due to formation of O2. Commercial fuming acid usually is quite dark red/brown, containing a
lot of NO2, so that the decomposition reaction with formation of O2 does not occur. But the red fuming acid is even more corrosive.
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PirateDocBrown
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No, I think that the use of excess bisulfate (about 3x by weight that of the nitrate) prevents much of the caking problem. The unreacted bisulfate
(and its water of crystallization) just sits happily in the reaction flask.
I get very good yield of azeotropic acid. What little NO2 I get gets captured as well, this then is mixed with the distillation heads, and this dilute
acid is used for utility in the lab, until I make another acid batch, when it is carried forward.
I would imagine that if you desired fuming acid, you'd have to start with H2SO4.
You don't need peroxide at all. I simply use it to scrub my offgas, and make a bit more acid. Vent your offgas, if you like.
Typically, I use 130g or so of NaNO3, and 450g (i.e. 1 pound) of bisulfate. I usually get around 120g of acid, and it measures about 1.4 g/cc, which
is close enough to azeotropic. Plus a few mLs of distillation heads, which I save.
| Quote: Originally posted by VeritasC&E | | Quote: Originally posted by PirateDocBrown | I use NaNO3 and NaHSO4, both really cheap. KNO3 would be fine, also. I use an excess of the bisulfate, and get 80% + yields. Slow and low heat.
I do it notionally "dry", but in fact add whatever dilute HNO3 I have laying around, to bring up concentration. NO2 waste gas gets led though 28%
H2O2, to make more dilute acid as I go. |
That's a good yield!
How much do you think you would get without using any H2O2?
Do you have any feedback regarding the challenges related to caking mentionned by Woelen?
"The disadvantage of using NaHSO4.H2O is that more solid stuff remains behind, whuch can form a nasty hard cake in the flask and may require stronger
heating."
|
[Edited on 8/16/22 by PirateDocBrown]
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VeritasC&E
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| Quote: Originally posted by woelen | What is best for you depends on many things. Is the H2SO4 the cost-determining or hardest to get reagent, or is it the nitrate salt? How much time do
you want to spend on the process? How much do you make in one batch?
My first guess would be that if you really need fuming (nearly anhydrous) acid, then just make it in one go. Concentrating more dilute acid with H2SO4
and distilling it off will also lead to decomposition. It is just, that the azeotrope is much more stable than the pure acid. Pure HNO3 slowly
decomposes, with formation of NO2, H2O and O2. At its boiling point this effect is quite strong. The azeotrope, which is a mix of HNO3 and H2O does
hardly suffer from that and it can be boiled hardly without decomposition.
If you prepare the fuming acid, then keep in mind that storing this is a pain in the ass. It eats nearly every cap you can imagine, and it cannot be
safely ampouled, because it slowly builds up pressure, due to formation of O2. Commercial fuming acid usually is quite dark red/brown, containing a
lot of NO2, so that the decomposition reaction with formation of O2 does not occur. But the red fuming acid is even more corrosive.
|
This is good information and answers my curiosity about where the losses mostly come from. It also conforts me in targeting only azeotropic HNO3 to
stock for the overwhelming majority of applications my very simple level needs it for.
Nowadays even the most basic reagents are getting hard to get and even the cheaply mass produced most basic chemicals for economy are getting very
expensive (a tragic regression of science and freedom for a deliberately engineered economic/social regression at the hands of the corrupted mafia
that is infecting the western world).
I'm quite sensitive to time but I'd rather use an efficient method and make a 20 year forward batch of a storable basic chemical* and then never think
about it again.
*in this case it would be azeotropic HNO3, a tiny proportion of which would be dried in minute amounts when needed for the rare and tiny uses I ever
make when it critically needs to be above that.
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VeritasC&E
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| Quote: Originally posted by PirateDocBrown | No, I think that the use of excess bisulfate (about 3x by weight that of the nitrate) prevents much of the caking problem. The unreacted bisulfate
(and its water of crystallization) just sits happily in the reaction flask.
I get very good yield of azeotropic acid. What little NO2 I get gets captured as well, this then is mixed with the distillation heads, and this dilute
acid is used for utility in the lab, until I make another acid batch, when it is carried forward.
I would imagine that if you desired fuming acid, you'd have to start with H2SO4.
You don't need peroxide at all. I simply use it to scrub my offgas, and make a bit more acid. Vent your offgas, if you like.
Typically, I use 130g or so of NaNO3, and 450g (i.e. 1 pound) of bisulfate. I usually get around 120g of acid, and it measures about 1.4 g/cc, which
is close enough to azeotropic. Plus a few mLs of distillation heads, which I save.
| Quote: Originally posted by VeritasC&E | | Quote: Originally posted by PirateDocBrown | I use NaNO3 and NaHSO4, both really cheap. KNO3 would be fine, also. I use an excess of the bisulfate, and get 80% + yields. Slow and low heat.
I do it notionally "dry", but in fact add whatever dilute HNO3 I have laying around, to bring up concentration. NO2 waste gas gets led though 28%
H2O2, to make more dilute acid as I go. |
That's a good yield!
How much do you think you would get without using any H2O2?
Do you have any feedback regarding the challenges related to caking mentionned by Woelen?
"The disadvantage of using NaHSO4.H2O is that more solid stuff remains behind, whuch can form a nasty hard cake in the flask and may require stronger
heating."
|
[Edited on 8/16/22 by PirateDocBrown] |
Thank you!
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VeritasC&E
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Any noticeable difference between NaNO3 and KNO3 or are both processes fairly similar?
Does anyone have experience with both to compare yields?
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Herr Haber
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| Quote: Originally posted by VeritasC&E | Any noticeable difference between NaNO3 and KNO3 or are both processes fairly similar?
Does anyone have experience with both to compare yields? |
Though I never compared yield, there is some info in the forum (I believe) in the picric acid threads.
Basically: NH4NO3 > NaNO3 > KNO3
The order to get rid of the cake is the same. Ammonium being easiest to dissolve and potassium.... well, I broke a flask while moving the cake around
once.
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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yobbo II
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I have read on the forum that ammonium nitrate gives 'lower quality' nitric acid. Would this mean there is more water in the finished acid (more
dilute/less fuming)? or something else.
Perhaps more sulphuric acid would help if it's more water in the finished product that is the lower quality issue.
Yob
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PirateDocBrown
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If you use ammonium nitrate, some ammonia can dissociate and come over to dissolve in the product, reacting to reform your ammonium nitrate. So you
would get less pure acid.
Calcium nitrate would give an insoluble calcium sulfate mass in the reaction flask. Messy.
Stick to sodium or potassium.
I get cheap sodium nitrate fertilizer, last I paid was $8 USD for 4 pounds, maybe 5 years ago. Potassium nitrate stump remover at that time ran about
$5 USD a pound. So I use sodium. More moles per pound, anyway.
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j_sum1
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FWIW, I have experienced a greater problem with foaming using KNO3 than NaNO3.
Annoying since the sodium salt is a lot more expensive.
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VeritasC&E
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| Quote: Originally posted by j_sum1 | FWIW, I have experienced a greater problem with foaming using KNO3 than NaNO3.
Annoying since the sodium salt is a lot more expensive. |
It's useful to know. All the cheapest things are getting expensive in these times. A funny effect is that it sometimes erodes such price differences.
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