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a123x
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Nitric acid
I've found a new way to make nitric acidof high concentrations and purity. It requires sulfuric acid, and either Ca, Sr, or Ba nitrate. Its simple
really, Ca, Sr, or Ba sulate are insoluble so adding Ca(NO3)2 to sulfuric acid of an concentration and you can get that same concentratio of nitric
acid back with CaSO4 precipitating. Then its just a matter of filtering. So if you can get 98% sulfuric you can make 98% nitric with nothing dissolved
in it and no distillation required.
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TheBear
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I've also read some about this method. Does anyone have any experience with this method using Ca(NO3)2?
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DeusExMachina
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shouldn't this be in the chemistry forum?
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BASF
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The "precipitation-nitric" - A tale of hope
This method is far from being new.....but i also once gave it a try.
It seemed like a geniously simple method to me at first.......
I´ve experimented a lot with these precipitation-reactions for nitric acid, but experienced that this method sucks heavily.
The only way i could imagine working would be to use a porous glass-filter with vacuum sucking device.
If u experiment a bit yourself you will see very soon that the volume of the developed HNO3 is not enough to decant it off, even with altering the
precipitate you will not be able to decant more than a few percent of the whole liquid in the slug.
The reaction product is a thick white paste and it is very important to use fine powdered, dry Ca(NO3)2.
As you mentioned, Ba(NO3)2 is also an option, with slight advance to the other method, because of the extremely low solubility of BaSO4, even in
concentrated mineral acids.
-But on the other hand: Ba(NO3)2 is very toxic and expensive, although i have to admit it can be made via:
BaSO4 + 10-fold excess of Na2CO3 with little water; cooking for 1/2hour > BaCO3(insoluble in cold water)
BaCO3 + dilute HNO3 > Ba(NO3)2
Other methods i have been trying were extraction with solvents such as acetic acid and the like.
I had to experience that these multiple extraction methods have a huge problem in the 2nd step when u try to seperate the acetic acid from the nitric
acid.
As it was fairly cheap, i first tried extraction of the acetic acid with toluene, which worked fine with 69% commercial nitric acid in the mix with
glacial acetic acid.
Later then i had to come to the conclusion that these extraction methods are very very sensitive to contaminations of inorganic salts, such as rests
of unreacted Ca(NO3)2 and also unreacted sulfuric acid.
Even the slightest contamination with these, may it be in the order of only a few mg per 100ml cause the whole thing to fail and it won´t mix any
more.
But, it has to be mentioned that the E&W-forum discussed some other, though more extensive extraction method using methylene chloride.
Several ways of removing the methylene chloride from the mix can be used, from freezing the nitric out to letting the methylen chloride evaporate.
As long as you can get hold of bigger quantities of methylene chloride it would be fine.
My last thought of how to use the precipitation method was to mix the thick slug with 1 or 2 fold its volume of glacial acetic acid and use it for
different nitrations as is.
Or, if u mix it with even bigger volumes of acetic acid, u could yet decant the mix carefully, giving a dilute solution of anhydrous nitric acid in
glacial acetic acid which had some advantages to the slug due to being it a clear liquid, not a thin slug........but i fear this would slow down the
rate of reaction for nitration and lower the yield.
But at last, this is one of my experimental favourites, and i´m sure some further experimentation on it would show some interesting uses for it...
HLR
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Polverone
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One other way of making Ba(NO3)2 is to heat BaCO3 with NH4NO3 and a minimal quantity of water at high temperatures. This method is not very fast, but
it doesn't need any nitric acid.
A (perhaps silly) question: can the precipitates be aged to obtain larger crystals? I know that sometimes letting precipitates stand for a long time,
especially with mild heating, will cause larger crystals to form instead of the extremely fine particles that you may have initially. I would
especially wonder about using this method with calcium nitrate since calcium sulfate is at least somewhat soluble. I wonder if a few days just sitting
at (say) 40 degrees Celsius would lead to a larger, more easily filterable precipitate, or even one that liquid might be decanted from.
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BASF
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No silly question at all.....
I tried altering the precipitate in the hope(as you mentioned) it could then settle to a higher degree and make decantation of at least some ml of
nitric per batch possible.....
So far, this has definitely failed.
It seems to me that the CaSO4-precipitate alters very quickly(i guess its a matter of hours), but the effect on settling was hardly noticeable at all.
But when it comes to filtering, it might be a good idea......i believe it would also extend the life-expectancy of precious glass-filters...
Maybe glass-filters could be cleaned with hot conc. H2SO4 sucked through as CaSO4 is quite good soluble in it making a complex-anion.
Anybody interested in the Ca(NO3)2/H2SO4-method may also take a look at
the Ca(NO3)2-synth in the library, which makes use of NH4NO3-fertilizer/CaO(lime).
http://sciencemadness.org/library
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a123x
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I don't have any calcium nitrate, I'm intending to make it with NH4NO3 + CaOH. Not having calcum nitrate I decided to do a test with CaCl2. I made a
solution of CaCl2 and added some sulfuric to it which of course resulted in plenty of white precipitate. As a filter I decided to use a model rocket
parachute that I had which is made from nylon if I remember correctly. It worked beutifly as a filter, there was actually a large excess of CaSO4 in
it which caused it to filter very slowly but just taking a plastic cup and pressing down on the glob of moist CaSO4 squeezed the HCl solution out and
through the filter. The filter wasn't damaged or anything, and there was only a very slight amount of CaSO4 that got through. I'm not sure why this
wouldn't work to filter CaSO4 from nitric acid unless nitric acid damages nylon.
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lucifer
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Can 100% HNO3 be stored for a long period if kept cool and in the dark or will it very slowly decompose into NO and H20.
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BASF
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lucifer: it won´t decompose under these conditions.
a123x: hmm your method is quite interesting.......maybe one could use a foil of a more resistant material, poly propene("poly propylene, pp") for
instance or pvc which would be even more resistant in my opinion, which has little holes in it made by just stinging needles into it(very fine needles
could be made of glass pipes).
This reminds me a lot of kneeding dough and cooking after all, hehe
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a123x
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Yeah, as it turns out the HCl mildly damaged the parachute but sulfuric puts holes through it in a few seconds. I don't actually have any nitric handy
to test it. The sulfuric is stored in a polyethlyne bottle so I figure that it should hold up to nitric acid too, and thin polyethlene sheets are easy
to get. Really a cloth made of those materials would be better though since it would work much more easily as a filter but I can't think of any where
that polypropylene, polyethlene, or teflon cloth could be gotten.
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BASF
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i tend to say that PE is not applicable for this action, sulfuric acid is one thing, 100% nitric acid another.....
But why not try PVC?
-It is far from being ideal, but maybe good enough for a single filtering.
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a123x
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Actually I was just looking at a chart about chemical resistance and it seems that PE has a better resistance to 70% nitric acid than PVC does. I
might go a different route anyway. I'm thinking of taking some glass and breaking it up into small bits and then makinga filter using that. From what
I can tell of the nature of the precipitate/liquid mix that forms it might work. When it isn't too thick the liquid should be able to flow through the
filter leaving most of the sulfate at the top. After that point the mix is pretty thick and requires being pressed t squeeze out the liquid where the
thick sulfate mixture isn't capable of flowing through the filter. There has to be a way to solve this problem other than distillation.
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BASF
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Strange. I expected PE to be less resistant than PVC to nitric acid but if the chart says so.....
BTW, in the past i have also thought a lot of how to press out the few liquid that the slug contains.....you cannot imagine what i have
tried.....beginning with syringes, paraffine-filled u-pipes, silicone-squeezes.....never ended up with more than a few drops though.
Maybe u could press it better through your "foil-filter" if u wrap it with the foil like a bonbon.....know what i mean?
-This could be a simple method with the advantage of having the slug protected from moisture and also, there would be less poisonous HNO3-fumes to
struggle with.
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Microtek
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How about using a centrifuge to separate the CaSO4 from the HNO3 ? There would be some work involved in building the machine, but a centrifuge can be
a quite useful thing in a lab... At high enough acceleration, the precipitate is compacted into a pellet at the bottom of the flask.
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BASF
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I guess this could be made with technic-lego(we all have played with it..) which i believe is also a good thing when you want to build your own
stirring device or even your own remote robo-hand for handling dangerous substances.....
Of course, the plastic parts have to be protected against heat above 50°C, organic solvents, nitric acid and the like, but maybe a coating with wax
or some other coating that could maybe be sprayed on it would do part of the job.
Wrapping it in aluminum foil could also help, but does not protect against corrosive vapours, such as those from nitric acid.
Back to the centrifuge.....
Good idea as you won´t need any filtering but i also think the problems are the vibrations, even with well-working counter weight.
Anyone having done some analytical lab course on university or at school, knows what i am talking about - Even the industrial products suffer from
heavy vibrations, often moving around the table while working.
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a123x
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A centrifuge would be nice but I don't have access to one and I don't think I'd be very capable of building one. I did finaly think of something easy
enough to get that might make a decent acid proof filter, fiberglass insulation. I looked up some information about it online and the only problem
would be the phenol-formaldehyde that binds the glass fibers together. I figure if the acid harms phenol-formaldehyde then sulfuric acid might be
usable to remove it from the glass, if it is neither harmed by nor harms the acid it could just be left on. The only problem is if it messes up the
acid in which case it would need to be removed by solvent. Does any one know if there is any particular solvent that would be best at dissolving
phenol-formaldehyde?
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BASF
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Does any one know if there is any particular solvent that would be best at dissolving phenol-formaldehyde?
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I have no specific reference for this, but i guess phenol-formaldehyde could eventually be dissolved in glacial acetic acid.
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DeusExMachina
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I havn't read this whole topic yet so I don't know if this has been talked about or not. I just found out that HNO3 can be formed by oxidizing
ammonia. How strong does the oxidizer have to be? also, what glass ware or equipment do I need for this?
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Rhadon
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DeusExMachina, sorry to disappoint you, but it's not that easy. The oxidation of NH3 is an industrial process which is not applicable for
use in a small laboratory.
Anyway, I'll briefly describe the reaction.
NH3 is oxidized with the oxygen that is contained in the air at 800 - 900 °C (usually with Pt- or Pt/Rh-catalyst), preferrably in an
atmosphere with increased pressure, to NO. The NO is also oxidized by the oxygen which is contained in the air to form NO2, which can then
(under increased pressure; still containing unreacted oxygen) be lead through water to yield HNO3 with a concentration of 50-68%.
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DeusExMachina
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sounds complicated to me... have you heard of anyone making it?
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Rhadon
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No. Like I wrote above: It's an industrial process which cannot be carried out in a small lab.
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BASF
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DeusExMachina, sorry to disappoint you, but it's not that easy. The oxidation of NH3 is an industrial process which is not applicable for use in a
small laboratory.
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No!! It CAN BE MADE in laboratory.
I can tell of at least two experimenting books descrbing relatively simple methods for lab preps.
The most important thing is the catalysator.
This is not that difficult.
Buy 50mg platinum wire(available from chem supplyers quite easily), hammer the wire flat to increase its surface.
Then it is dissolved in hot aqua regia and left for some days til it is completely dissolved.
Then the resulting hexachloro platinum acid is neutralized with ammonia and a precipitate forms, which is directly adsorbed by diatomeous earth.
Finally, the dried catalyst is glowed with the effect, that metallic platinum is left on the surface.
A fire-resistant test pipe is filled with the catalyst and heated to approx. 700°C.
The needed NH3 should be generated relatively dry using some ammonium salt mixed with CaO and the right amount of water.
They warn not to use pure oxygen instead of air, because this can very well result in an explosion.
The two procedures do not cool the reaction gases to increase the yield, as red brown gases can easily be seen though.
Also a Fe2O3- catalyst on the same carrier can be used.
Then the working temp is more than 100°C higher.
Finely divided Fe2O3 can be made by mixing solutions of Fe3(SO4)2 with NaOH and then adding H2O2.
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Rhadon
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The procedure still doesn't seem to be applicable for small laboratories to me, but that should depend on the definition of "small".
Thanks for the hint with the catalyst. Do you know of anyone who has tried the whole procedure or even tried it yourself? If so, where the
NO2 yields acceptable?
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Praetorian
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Has anybody problems with red fumes NOx during distillation of the anhydrous HNO3 ?(I can't help myself, I think the most effective and simpliest
methode is distillation with H2SO4 under suction). No problem. Simply add a few urea into reaction mix. Urea reduce NOx to N2 and carbon dioxide.
Excess of nitrous acid is commonly remove after diazotization reaction in a similar way.
The cyanides are good to digesting!
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a123x
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NO2
Well it has taken me a while bfore I had the time but I finally went out ad got some Ca(OH)2 to make calcium nitrate and some fiberglass cloth to use
as a filter so hopefully I'll have results on whether the precipitation method works. Another thing is, don't bother wit oxidation of ammonia for
nitric acid producton as it requires the high temperatures and all that crap. Something similar that you might try though is the electric arcmethod of
producing NO2. All you'll need is a flyback transforme, an oil burner ignition transformer, NST, or even a microwave oven transformer. You run the arc
in a closed container causing NO2 to form and pump this into a cooled container with water vapor being pumped in. HNO3 forms and precipitates. I would
have tried this except my flybacktransformer circuit broke and I haven't gotten it working. I think I still might have a working NST and I know I
still have a working MOT. That page gives a description of producing NO2 in such a fashion.
http://kronjaeger.com/hv/hv/exp/no/index.html
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