HNO3 your way

[mr.pyro]

Mr. Pyro ask if anyone has used vacuum distilation for NA and what was the results? I did it with SA/68% NA and strong vacuum It worked good if dry ice cooling of the reciveing flask was used. I think NA has a hard time condensing when under strong vacuum. (< 50 torr)

(best if done twice) and whih excess SA.

You say you had to use dry ice? I tried it under strong vacuum and it boiled over way to fast. It hardly had time to condense and ended up mostly getting sucked into my gas traps. The ph was was low when I was measuring them. I am thinking of getting a vacuum valve of somesort to regulate the vacuum pressure. Does anyone know of such a thing?

[Boomer]

Just have any valve at the pump in parallel to the tube going to the vacuum adapter of the setup. Heat the mix to a moderate temp and close the bypass slowly until it starts boilling. From the temp reading you can calculate back (or look up) the vacuum level.

 

With too strong a vacuum you lower the boilling point of pure nitric acid down to room temp. Without dry ice or at least a -20C recirculating glycol flow in the condenser, it simply won't condense.

 

Personally, I never bothered with vacuum distillation for nitric. Given enough time and some excess sulfuric it works like a charm, at least with AN. The last NOx can be purged out if needed, and 1-2% water don't hurt most nitrations. Regular yields over 90% for esters and around 70-80% for RDX say it all.

 

If 2% water spoil the reaction it is time to replace sulfuric acid with Ac2O anyway.

[mr.pyro]

Thanks Boomer, I think my pump is too strong for this, I will try as you say. I was boiling water and alch and the nitric at room temp so I'd think thats why I had hardly any condense.

 

Seems like it was just too much of a good thing.

[tentacles]

I'm wanting to whip up some nitric acid for making lead dioxide anodes, and maybe some NC, barium nitrate, etc - would this distillation setup work for me? Of course, with a receiver flask and seal.

 

http://www.apcforum.net/files/3826_1_sbl.JPG

[hashashan]

It would be smart to have a thermometer but yes this setup should work

[tentacles]

I'll have to organize one, then - thanks!

[hashashan]

However it has to be an all glass cork-thermometer ... It is expensive though .. I still don't have one

[asilentbob]

Teflon tape ... You want air to be able to escape though at the bottom of the condenser... otherwise you would basicly be pressurizing a big glass bomb. *seemed like you meant that you wanted everything completely sealed, if thats not what you meant, don't sweat explaining*

 

Getting my org set in around 4 days... wont have time to use it for a hwile what with school and work... but i will likely use it for a good amount of nitric at some point... My biggest problem is only having like 2 ground glass bottles for storing chemicals presently...

[tentacles]

Teflon tape ... You want air to be able to escape though at the bottom of the condenser... otherwise you would basicly be pressurizing a big glass bomb. *seemed like you meant that you wanted everything completely sealed, if thats not what you meant, don't sweat explaining*

 

Getting my org set in around 4 days... wont have time to use it for a while what with school and work... but i will likely use it for a good amount of nitric at some point... My biggest problem is only having like 2 ground glass bottles for storing chemicals presently...

asilentbob: I was planning on using my vacuum flask as a receiver, and at FrankRizzo's suggestion, a water aspirator to supply some vacuum.

 

The thermometers are reasonable, but the 24/40 adaptor is insane. I'm thinking about getting a piece of teflon rod and making one myself. It's still like $15 for a piece of 1.25" teflon 6" long, but I'd have the extra to use for other pieces, like a seal from the bottom of the condenser to the vacuum flask.

[asilentbob]

You would have to carve it really well to get a good seal... I was implying normal cork or rubber stopper with a hole through it... and wrapped tightly in teflon tape... the vapors will still attack the rubber or cork... but in the case of rubber you would just get some black stuff dropping into your flask... and since your distilling it... you going to still get clear HNO3.

 

Someone needs to invent cheap reliable Teflon paint... or similar... perhaps like that tool handle DIY rubber coating stuff... but not... because the Teflon would not dissolve...

 

IIRC Nitrocellulose filter papers are used for very acidic enviroments... perhaps a few coatings of NC laquer on cork or rubber stoppers would help... problem is that when the NC laquer dries it would be rather brittle and would probably break when you push it into a flask that doesn't have ground glass...

 

You might be able to get a piece of wood and carve it down really close to the required size... with a hole for the thermometer of course... then coat it in NC laquer... well... then seal the hole around the thermometer better with teflon tape when you put the thermometer in... so it doensn't slide out and all... then wrap the outside of the wood plug with teflon tape and put it into the ground glass female joint. Then only NC coated wood, teflon, and the thermometer glass would be touching the vapors...

 

I never used a thermometer on my retort... I just kept the temperature low and constant... when it was as low as it would go... and still too hot i would raise the retort farther away from the hot plate... oh and i always shielded the retort neck and recieving vessel/ice from radiant heat with well placed aluminum foil. Then again i used Ca(NO3)2/H2SO4... and it seems in my experience that the lease NO2 is produced this way... the inside of the retort is prefectly clear, no red tinge at all... and the HNO3 is strong and crystal clear.

 

Edit: I wouldn't trust that rubber stopper for the condenser connection to vacuum... if you adjust your vacuum so that your not pulling at max you might be ok... ie having a needle valve on a T connection or something before the vacuum source to let in a little air... a vacuum gauge would be nice... I really want to get one for my DIY aspirator... but i have only seen them in full brake bleeding kits OTC... or off ebay... might just break down and go ebay...

[tentacles]

Surplus center carries vacuum gauges. surplucenter.com

 

I was going to machine the teflon on my lathe, make a nice fit, and then wedge the thermometer (or tubing) in with some teflon tape to make a good seal. If I have vacuum on the system, then the seal can be held partially by it.

 

Unfortunately, teflon can't be painted, there aren't any suitable solvents. It CAN be powder coated... if you can find the product in reasonable quantities.. Dunno what the purity is like, I've heard non-virgin teflon doesn't hold up well to nitric acid distillation.

 

The NC lacquer is a good idea, it would just become more nitrated by the exposure. If you wrap it in teflon tape as well, that should help make a good seal without needing excessive force (crushing the NC coating).

 

If you want to do it under reduced pressure, get a vacuum aspirator - see FrankRizzo's post below for a great source. It's just a venturi that is powered by your faucet. they make glass ones ewfor about $30 but the plastic type work fine.

[FrankRizzo]

WOAH!! Do *NOT* use a waterbed drain pump for vacuum distillations. Suck-back can and will occur without a check-valve. Cold water splashing into hot glass filled with hot concentrated acids will cause a HORRIBLE mess.

 

Buy one of the poly plastic ones with a check-valve. I bought this one from Sciencekit.com a couple years ago. I think it was ~$16 after shipping.

 

http://sciencekit.com/images/250/CD6166705.MS.JPG

[tentacles]

My bad, I edited my post, those pumps come to $19.50 with shipping these days. There was a guy with one on ebay for $8 shipped, but of unknown plastic - it looked like glass filled nylon. I didn't want to get one that could possibly dissolve from the nitric acid vapor going through it.

[asilentbob]

http://www.frogfot.com/misc/waterjetvac.html

 

They are pretty easy to make... you could probably make one from all plastic parts from the local hardware store. I used brass very similar to frogot's one. The top water inlet one.

 

The condenser should be working well enough that HNO3 fumes reacting with the aspirator shouldn't be a problem... You can always flush it out with water before storing it though so that any HNO3 is carried away... Or i suppose you could coat the inside with a film of plastic somehow.

[crazyboy25]

i plan on making nitric acid by heating sulfuric acid and kno3 in a jar in a hot water bath and letting it condense on a plastic ziploc bag on the top i have 2 questions:

 

 

1. will a ziploc bag stand up to the nitric acid?

 

2. what would you suggest i use to collect the condensing nitric acid (something around the house or easily obtainable)

[tentacles]

crazyboy:

 

1. Not for long if it's pretty pure HNO3 condensing..

 

2. Something glass. there is no other household option, period. After all, the point is to obtain fairly pure HNO3, so I would not reccomending using stoneware or anything that isn't quality glass.

 

I tried the glass in a jar method (what you are describing) and it doesn't work very well. How strong do you need your HNO3? You could check local hydroponics/greenhouse shops for "Technaflora PH down" (30% nitric). They may have another brand of nitric, and some greenhouse suppliers simply sell it as nitric acid. Also some farmer coops sell it to clean milking machines. If you're really just wanting to make your own, you really need a distillation setup for it to be effective and safe.

[crazyboy25]

well weknowpyro use saran wrap which is thinner than a ziploc bag also i dont need very much just a few mls (10-30) and i plan on using it right after i make it.

 

70% is good but i have heard this method yields close to 80-90% which works great too (i can just dilute it.)

 

my method will be a mix between frogfot, brainfevert, nighthawknthelight and information i picked up.

[weknowpyro]

Yeah, Cling film (saran wrap) works fine, although it can rip open pretty easily. I always found that making nitric acid that way; tended to have low yields.

 

I had a thought the other day that maybe for a cheap source of more concentrated nitric acid, someone could buy 30% HNO3 and then use brain fevers method but with the dilute acid. Then heat the acid and allow it to evaporate and condense.

Would most likely yield a high concentration of nitric acid.

[Mumbles]

You'd need to add sulfuric acid to the dilute stuff to get any appreciable concentration. I'd also suggest getting a real distillation apparatus if you are serious about making nitric acid. I obviously have a great deal of respect for brainfever, but the method he presented is a rather clandestine one. It wont give the highest concentrations or purities possible.

[weknowpyro]

Yeah, I've been searching for one recently. I was doing some work today and was looking through my equations and was wondering if there was some way of calculating the concentration percentage of homemade nitric acid. So I came up with this; please say if you think it makes sense or not.

 

2KNO3 + H2SO4 ---------------> 2HNO3 + K2SO4

 

KNO3-

n=m/Mr n= 41g/101 n=0.406 moles

 

41g = 13.6ml

 

C=n/v C= 0.406n/0.0136 C= 29.8 mol/dm3

 

H2SO4-

0.406/2 = 0.203

 

C=n/v C= 0.203n/0.05 C=4.06 mol/dm3

 

 

This is the part I get slightly confused with. I added both concentrations together, as they are a solution.

29.8+4.06 = 33.86 mol/dm3

 

HNO3-

0.406n/0.015 C=27.1mol/dm3

 

Finally-

27.1/33.86 = 79.9%

 

So you would theoretically produce 15ml's of 79.9% nitric acid.

[Mumbles]

Nope, doesn't work like that. Some corrections:

 

First off all density of one reactant has absolutly no influence on the density of the product.

 

Secondly, bulk density does not equal product density. If you fill a liter bottle with marbles, it would weigh say 2 kilograms. Now if you melted all those marbles down it would take up less space. Same mass for less space gives a higher density. If you're going to do anything like this(not that it would work), you'd have to use actual density not apparant density or bulk density. KNO3 has a density of 2.109g/mL. Apparantly you either messed something up on the volume measurement, or you have super dense KNO3(or non-pure KNO3). It should be around 19mL.

 

You have really dilute acid if .203 moles of it is 50mL. It'd actually be even less dense than water.

 

mol/dm3 is also known as moles per L or Molarity. The molarity of sulfuric acid is aroune 18,4. Nitric Acid is around 24 at 100%

 

If everything else being wrong isn't enough, even your formula is wrong. Sulfuric Acid will only donate 1 hydrogen in this reaction. The temperature for:

 

KNO3 + KHSO4 ---> HNO3 + K2SO4

 

is higher than the decomposition point of nitric acid.

[weknowpyro]

Oh well, thanks for letting me know. Glad I checked it over before trying anything with this.

Looks like I pretty much mucked it up in the densitys.

[tentacles]

weknowpyro: distillation setups aren't too horribly expensive on ebay - put in some time looking at ebay express and at sellers' stores. Ask if they will sell off ebay - technically it's not allowed but a lot of people will do it, because they save so much from ebay fees and the price will reflect this.

 

Having tried it (briefly) without vacuum, I'd suggest not even attempting the nitric distillation without it. It just goes so much faster and the NO2 production is so much lower. It's a bit of a bitch if all you need is a few ml.. If that's the case, put a shot glass in a canning jar and try it in there. put saran over it with ice, etc, and place it in a bath of warm water outside, and let it go. It won't be pure, it won't be efficient, and it takes just about forever.

[crazyboy25]

i want to be safe and efficient but i only want a few mls the cheapest source i could find nitric acid for is $50 for 500ml which is pretty good but im kinda strapped for cash i would love distillation equipment but the cheapest i found it for on ebay was $120

 

 

 

bottom line i will go ahead if it doesn't work or works horribly (acid unusable yielding only 1ml in 5 hours i will stop and buy it.

[tentacles]

What % hno3? I found it cheaper than that with a little effort; I don't know if your price includes shipping though. That can really kill a deal. I can't remember where it was but I've seen 1L 68-70% for $40 or so. Try photography chemical suppliers if you're interested in that route. Another place to try would be farmer co-op type places; 68% is used to clean milking equipment. Also try greenhouse fertilizer suppliers; it's often used to regulate PH in hydroponics, especially large commercial systems.

 

I don't really know what you want the HNO3 for, so it's hard to recommend anything. I can only think of a few things that really require more concentration than 68%, and they aren't appropriate to discuss here.