When I'm dissolving sterling silver in nitric acid, alot of NOx gasses are released.
Am I right by thinking that if I run the gasses through a condenser, HNO3 will form as a distillate? Sorry if I sound like newbie.. I have read that
you can bubble NOx gasses through H2O to make dilute HNO3. Any reason why a graham condeser wouldn't produce a higher yield?
Thanks
I just run my first batch of HNO3 today, and ended up with 138ml of 55% HNO3, from 200ml of 72% H2SO4 & 170g of KNO3. (2hr run time, temp stopes
from 112 to 100 & distillate became irregular)
Think next time I'll let it run a little longer.
[Edited on 13-7-2011 by Dre_co]
[Edited on 13-7-2011 by Dre_co]woelen - 12-7-2011 at 22:26
NOx gases alone do not give nitric acid. But if you lead them through water and allow sufficient oxygen to go with the gases, then you indeed get
nitric acid. Leading them through a condenser is not that interesting, it may cool down the gases somewhat, but no nitric acid will condense. Mix the
gases with sufficient air and bubble them through water.
---------------------------
Your yield of 138 ml of 55% HNO3 is decent, given the starting materials. Of the H2SO4 only one proton is used for making HNO3, the other ends op in
KHSO4. Based on used amount of KNO3 your yield is somewhere between 85% and 90%.Dre_co - 12-7-2011 at 23:02
Thanks woelen,
Do you know of any way to mix oxygen before bubbling? All I can think is to lead a hose from an elymer flask into either a second flask or beaker
containing H2O.
Would this allow sufficient O2 into the mix? And would the yield be worth it on a relatively small scale?
I also read that about half the nitric is lost (while dissolving sterling) through gasses so I'd like to find a way to collect it.
I have thought about ways to recycle it, ie. condensing on a cold watch glass on top of the beaker etc.
Thanks for your assessment of my HNO3 yield, it's going down in my notebook for future reference. blogfast25 - 13-7-2011 at 04:05
I've been wondering if commercial thin bleach (4 - 5 % NaClO) would be a decent scrubber liquid for an NOx wash bottle. I'm making various nitrates,
also use HNO3 as an oxidiser quite a lot, and the NOx is a real nuissance. Bleach is slightly alkaline and a powerfull enough oxidiser to oxidise NO
to NO2. You'd get a weak solution of NaCl + NaNO3.
Any thoughts on that? Bleach is cheap but of course it's also quite weak and easily exhausted. Perhaps adding litmus indicator solution could even be
an indicator to point to exhaustion of the hypochlorite?
[Edited on 13-7-2011 by blogfast25]MrHomeScientist - 13-7-2011 at 05:20
Thanks woelen,
Do you know of any way to mix oxygen before bubbling? All I can think is to lead a hose from an elymer flask into either a second flask or beaker
containing H2O.
A better way to make nitric acid is to bubble the NOx into a solution of hydrogen peroxide - that makes the process a bit more efficient. I imagine
this provides the O2 for the rxn, so that you don't have to worry about mixing in air.Dre_co - 13-7-2011 at 17:25
A better way to make nitric acid is to bubble the NOx into a solution of hydrogen peroxide - that makes the process a bit more efficient. I imagine
this provides the O2 for the rxn, so that you don't have to worry about mixing in air.
Ah yes, similar to nurdrages video on YouTube? Any way of when telling all the H2O2 has been fully converted? Or just bubble what I have through,
then take a density reading? Anybody had any experience with this?Intergalactic_Captain - 14-7-2011 at 00:10
Never used bleach as a wash for NOx, but urea is pretty much an accepted standard. Cheap, found in more and more places (thanks to the fear of
ammonium nitrate), and useful for quite a few things... I've never really looked into the mechanism, but in my past experiments with distilling HNO3
it worked quite well as a wash, as well as an in-situ scavenger if things got too hot. I've found it quite effective at cleaning up semi-runaway
nitrations (EGDN and picric acid) as well.
The H2O2 idea intrigues me - I've thought about this in the past for HNO3, as well as for SO2 to sulfuric - Are you speaking in theoretical terms or
do you have any practical experience? The molar economy of xNO3 and H2SO4 is far better than copper/nitrate/HCL, but in terms of cost and layout it
may is a worthy contender for a hardware-store nitric acid method.blogfast25 - 14-7-2011 at 04:44
Thanks, IC...MrHomeScientist - 14-7-2011 at 05:41
Unfortunately no, I don't have any practical experience with making nitric acid. I did try it once reacting ammonium nitrate with battery acid, but
that was way too dilute to produce much of anything. Plus I hear ammonium nitrate tends to decompose and isn't ideal for this.
As far as the H<sub>2</sub>O<sub>2</sub> goes, yeah I heard about that from NurdRage's video. My comment about it providing
the oxygen so you don't have to blow air into it was mostly conjecture, but it makes sense to me. This is a reaction I've really wanted to try for a
while, since nitric acid is so useful yet hard to get. I've finally got some good distillation glass and "liquid fire" brand concentrated
H<sub>2</sub>SO<sub>4</sub> so it's on the to-do list.
Nitric Acid from Nitrogen Dioxide
AndersHoveland - 14-7-2011 at 09:18
Both nitric oxide and nitrogen dioxide would be oxidized by aqueous solutions of hypochlorite (remember that bleach contains both NaOCl and NaOH).
*however, nitrous oxide, N2O, would not be oxidized by bleach.
If NO2 is bubbled, together with dry air, into plain water, solutions of nitric acid can be obtained, up to around 74% concentration, after which the
concentrated solution will cease absorbing any more NO2. Nitric oxide, formula NO, can also be used instead, in which case it is best to allow the
nitric oxide to react with excess air, forming brown NO2, before being bubbled into the water. NO is a reactive gas which is spontaneously oxidized by
oxygen. Do not let the NO sit around too long, as it slowly disproportionates to a mix of N2O and NO2 after several minutes.
(2)H2O + (4)NO2 + O2 --> (4)HNO3
I have personally prepared nitric acid by this method, using the reaction of copper with 40% nitric acid to generate the NO2 fumes, and an air outlet
that was built into the university laboratory. The fumes are very corrosive to the rubber stoppers. The nitric acid prepared was over 70%
concentration.
A small piece of cotton was added to the acid, and more NO2/air was bubbled in. The nitric acid was found not to be capable of nitrating the cotton to
cellulose nitrate, indicating that nitric acid concentrations over 95% are certainly not achievable by this method.Dre_co - 14-7-2011 at 15:51
AndersHoveland, how long did your reaction roughly take? ((2)H2O + (4)NO2 + O2)UnintentionalChaos - 14-7-2011 at 18:31
Unfortunately no, I don't have any practical experience with making nitric acid. I did try it once reacting ammonium nitrate with battery acid, but
that was way too dilute to produce much of anything. Plus I hear ammonium nitrate tends to decompose and isn't ideal for this.
Ammonium nitrate is an excellent nitrate source for making HNO3 since it is fairly soluble in conc. sulfuric. The ammonium bisulfate byproduct will be
molten when finished if you distill at atmospheric pressure. If you were to use potassium or sodium nitrate, the product is a solid. If you distill
under vacuum, the ammonium bisulfate will remain a solid, however, as was my experience.
What is the maximum concentration of nitric acid that can be achieved by bubbling NO2 into 100% conc H2O2 ?
Would it actually theoretically be possible to obtain 100% conc HNO3 from such a reaction?
[Edited on 7-11-2011 by AndersHoveland]Chemistry Alchemist - 7-11-2011 at 02:53
I cant fully answer your first question but ill see how it goes... there would be calcium contamination in the acid if you done it this way tho...
unless teh calcium nitrate precipitates out of the hydrogen peroxide as its made...
I dont think you can obtain 100% this but NO<sub>2</sub>, pretty sure if you could get 100% concentration form it you would need 100% H2O2
or another high oxidizing chemical that adds oxygen to the NO<sub>2</sub> but does not react with the acid as its made... if you want high
concentration acid, you will need to heat a nitrate salt (pure) with concentrated Sulfuric acid and distill the Nitric Acid and it forms and even then
i dont think it will be 100% or if you can get 100%, pretty sure the highest ive heared is 70%AndersHoveland - 7-11-2011 at 03:07
Pure HNO3 can be made by reacting ozone and NO2 with a limited quantity of water. In fact, if there is no water N2O5 will result.
If you want high concentration acid, you will need to heat a nitrate salt (pure) with concentrated Sulfuric acid and distill the Nitric Acid and it
forms and even then i dont think it will be 100% or if you can get 100%, pretty sure the highest ive heared is 70%
99% HNO3 is possible from such a distillation, but it must be done at lower heat and reduced pressure if concentrations beyond the azeotropic
limit are desired. Heating to the boiling point causes irreversible decomposition of the pure acid, the resulting NO2, O2, and steam recondensing and
reacting back to only 72% conc HNO3 (near the azeotropic limit).
(note that the percentages in this post are merely rough estimations)
[Edited on 7-11-2011 by AndersHoveland]Chemistry Alchemist - 7-11-2011 at 03:20
i guess you learn new things ever day... well for me every few days thanks for
correcting me
