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Author: Subject: Nitric acid
BromicAcid
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[*] posted on 8-9-2004 at 17:42


Quote:
I don't know about that decomposition of calcium nitrate, usually nitrates decompose along the lines of

Ca(NO3)2 ----> CaO + O2 + 1/2N2


I know rikkitikkitavi corrected me further up thread but I was reading "The Chemistry of the Elements" and under the entry for calcium nitrate it lists the normal decomposition of it. If heated slowly first:

Ca(NO3)2 ----> Ca(NO2)2 + O2

Followed by if heating is continued:

Ca(NO2)2 ----> CaO + NO + NO2

However if heated quickly it would probably pass right though that nitrite stage and go to the total decomposition giving oxygen and nitric oxides and just as rikkitikkitavi said they probably dissociate readily at this temp but upon cooling you would be left with a large percentage of nitric oxide.

(Just kept bugging me after I read it, took me 30 minutes to find this thread.)

Edit: Hummm... 75th post to this thread and therefore according to my viewing settings my own page, not good, now I'm not in context with the rest of the thread and my point is partially lost. Basically this was just an example of me correcting myself and agreeing with another person.

[Edited on 9/9/2004 by BromicAcid]




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[*] posted on 20-10-2004 at 01:00


Sorry, about me scaring you with high temperatures, pressures and long times for NO2 + O2 dissolution, we don't necessarily want 100% acid. :)
A way to separate your HNO3 from the precipitate is to distill it with the plastic-film-over-vessel-and-beaker-underneath method described for production of HNO3 from NaNO3, KNO3, NH4NO3 and the like (distillation below boiling point - DBBP).
As I found out from someone's link, NH4NO3 can be decomposed catalytically by Cl- to give dilute HNO3 vapour.




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Quince
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[*] posted on 15-9-2005 at 10:47


Can the methylene chloride method be used to extract directly from the H2SO4/nitrate mix usually used for distillation of HNO3? Or will the bisulfates interfere?



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[*] posted on 15-9-2005 at 11:06


Yes, there were some aromatic nitrations using CH2Cl2, NaNO3, and an acid on Rhodium's site. I don't have the paper handy, but I think the PDF is on FTP2 in the Rhodiums PDF folder.

What is the problem with distilling 100% HNO3 from an equivolume mix of 98% H2SO4 and 70% HNO3? That's how I did it back in my college days for a prep of tetranitromethane from acetic anhydride and 100% HNO3. (back in olden times before everything caused cancer and chemicals were deadly national hazards)

[Edited on 15-9-2005 by Eclectic]
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Quince
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[*] posted on 15-9-2005 at 17:27


The problem is I don't have any dilute nitric acid; all my HNO3 this far has come from H2SO4/nitrate vacuum distillation. I'm trying to figure out if I can skip the distillation, as the aspirator uses up an immense amount of water.

I don't intend to nitrate with the mix. The dichloromethane is supposed to evaporate faster at a lower temperature than the HNO3. I could just put a vigreux column with an open top, and the flask in 50*C water bath.




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Eclectic
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[*] posted on 16-9-2005 at 05:03


68% is the azeotrope you get when you distilling nitric acid at atmospheric pressure from a mix of dilute H2SO4 and a nitrate. Just use your vigreux column without vacuum.

See: http://www.chemguide.co.uk/physical/phaseeqia/nonideal.html



[Edited on 16-9-2005 by Eclectic]
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[*] posted on 16-9-2005 at 06:31


Quote:
Originally posted by Quince
The problem is I don't have any dilute nitric acid; all my HNO3 this far has come from H2SO4/nitrate vacuum distillation. I'm trying to figure out if I can skip the distillation, as the aspirator uses up an immense amount of water.

I don't intend to nitrate with the mix. The dichloromethane is supposed to evaporate faster at a lower temperature than the HNO3. I could just put a vigreux column with an open top, and the flask in 50*C water bath.



You -=CAN=- skip the vacume. I have tested this for some time with some fairly good glassware and I get the same very, very light, lemon yellow acid with a vacume as without. I went up to as high as vacume as I could pull and it stayed the same as no vacume (faintest yellow) and all the labs utilizing that HNO3 were just fine.
On another note, I used to distill dichloromethane from a paint removed and get quite a bit of the pure product. When I use dichloromethane I can receive the HNO3 from it via distilltion at 40 C (no higher) thus I use a "hot pad" (for beds, bad back, etc); it keeps the temp at a perfect 104F and my distilltion is very clean and fast. I have stopped using a vacume entily as I had access to a really good pump and I just couldn't get 100% clear HNO3 without Urea....so I just use the Urea and live with it. It really does work fine.




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[*] posted on 27-9-2005 at 09:49


Found some impure nitrate in the basement (Osmocote or whatever, bulb feed, contains ammonium nitrate). I put some salt (I filtered it from the CaPO4 and organic casing parts and recrystallized it, if you can call it crystallized) in the bottom of a jar with H2SO4 with a smaller jar supported inside, with LDPE plastic covering it with ice. It's frothy and the vapor is brown at the moment... :o I've collected an ounce or two of distillate so far but it doesn't react with copper metal like HNO3 is supposed to...

Edit: Of the distillate I've collected so far, it does not react with copper but does produce a lot of white precipitate with Cu2O. :(

The apparatus at the moment has quite a bit of orange color to it, but last I checked not a drop was condensed. What the heck?

Tim

[Edited on 9-27-2005 by 12AX7]




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[*] posted on 27-9-2005 at 10:50


Redistill from H2SO4. It's probably just too weak to dissolve copper.
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sad.gif posted on 30-12-2005 at 15:22
Condensing Nitric Acid


Lotek and I were trying to create some Nitric acid. We used about 150ml of H2SO4 and about 250 grams of KNO3 in a round bottom flask and preheated the acid to just over 100 degrees C. We were expecting to condense the red Nitric acid; yet, the colorful gas only stayed in the flask and did not move through the condenser coils. As shown in this picture.

http://www.cyroxos.net/random/IMG_1469.JPG

The liquid in the flask was boiling, and there were not blockages in the flow to the condenser. The stoppers were sealed. We waited, yet, the (what I assume to be Nitric acid) liquid condensed on the sides of the flask and the glass rods, yet never condensed in the condenser. Are we just not waiting long enough? Do we need to apply more heat to it? What exactly are we doing wrong? What about the small diameter of the glass rods? could that be a problem

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[*] posted on 30-12-2005 at 15:36


I have had this same problem using a retort. The only advise I was given was to crank up the heat, and then bubble O2 through the NO2 contaminated HNO3, to make it clear..
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[*] posted on 30-12-2005 at 15:41


Not enough heating or maybe you not waited enough time. Brown gas does not condense, after some time most of gas will be colorless and invisible. This can be condensed to get nitric acid. Product will be red (or brown) as brown NO2 dissolves in nitric acid.

[Edited on 30-12-2005 by chromium]
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[*] posted on 30-12-2005 at 15:45


That brown gas is NO2 and its presence is normal when heating nitric acid.

Water/HNO3 should come off first if your mix is rich in water. When the pot concentration reaches 68% HNO3 (azeotrope) this should come off steadily at 120C until you are done.

You would have to be initially lean in water to get to just fuming nitric acid. Fuming nitric may require vacuum conditions to prevent decomposition. I have not made fuming HNO3 so can't say from experience. I only made the 68% acid.

I think you are just not waiting long enough. I used a straight tube condenser allowing a clean cut when the temperature reaches 120C. It seems like your helical condensor will have some holdup but it should do the job.

Search "Making own nitric acid" and you will pull up some experience that should be useful.

[Edited on 31-12-2005 by Magpie]

[Edited on 31-12-2005 by Magpie]

[Edited on 31-12-2005 by Magpie]




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[*] posted on 30-12-2005 at 16:05


Rubber stoppers will be eaten by nitric fumes. Wrapping your stoppers in saran wrap will stop this.

Your setup is not well suited for a distillation of something as sensitive as nitric. The small tube connecting your boiling flask to the condenser is rather thin, so it will air cool and mainly act as a reflux condenser, making you need higher heat to get the nitric fumes into the condenser, and higher heat will also decompose the nitric. Try getting a larger diameter glass tube for connecting the two, and or insulate the tube to prevent condensation here. Glass wool or cork will work for this. Insulating the top of the flask the same way would also be beneficial. For nitric, a nice, slow distillation gives the best product.




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[*] posted on 30-12-2005 at 16:15


I agree with rogue here that this synthesis is nothing to take lightly. My rubber thermometer adapter did suffer some degradation due to the nitric acid fumes. A keck clamp at a leaking ground glass joint was destroyed. Both NO2 and HNO3 are not something you want to breathe. I was very glad I had good ventilation (a hood).

If you are just after fuming nitric acid you will need vacuum conditions (I believe) which presents a whole other level of required equipment sophistication and experience. Just imagine a faulty RBF imploding full of nitric/sulfuric acid and you are standing in front of it without adequate protection. It would not be a pretty sight.

Aluminum foil will also act as insulation.




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[*] posted on 30-12-2005 at 17:09


...or my way of getting fairly decent grade Nitric Acid...never mind about the fancy condensing coil method...just take two pyrex flasks with stoppers and a long 3/8" pyrex tubes and have 1 of the flasks mixed with Nitrate/ H2SO4 and the other beaker empty in an ice bath slightly tilted downwards. I made 800ml of fairly good grade Nitric acid this way. It was nearly colorless with only a very slight yellow tint to it. You get Nitric acid very quickly this way because the air is able to cool the gases much faster using a larger diameter glass tube. I'm not saying that the condensing coil method doesn't work...no..of couse not. It just takes a much longer time--I don't find it nearly as effective.



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[*] posted on 30-12-2005 at 17:30


Also, a condenser like that works best in a vertical position, so that the nitric that forms drips out of the condenser and does not stay in the loops.

What is the other tube leading into your condenser for?

Magpie, fuming nitric does not actually require a vacuum setup, I have made small ammounts(<10mL, enough for my purposes) using only a 600mL beaker, a shot glass, and a plastic baggie. The method is on Brainfevers site.




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[*] posted on 30-12-2005 at 21:35


I have made fuming nitric acid by atmospheric distillation without problem. I used the standard mix of AN and SA (with a little extra SA), a 500mL RBF, 400W fiberglass mantle, and 300mm liebig, all with 24/40 ground glass joints. The acid came over with minimal decomposition, certainly far less than what is in that photo. It is yellow, I can take a picture if anyone wants to see it.

Someone else here did this a few months ago and concluded that decomposition is mainly from sunlight and that the whole vacuum thing is just a bunch of bogus science. I don't remember who it was, but I have to agree.
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[*] posted on 31-12-2005 at 00:44


I often use AN with H2SO4 and I get fuming Nitric acid. I've made all kinds of fun energetic materials this way. Right now I have 2.5 L of fuming Nitric acid on the brew. You do need a safe environment to do this in.. not inside a garage with flammable solvents and liquified petrolium tanks. BAD BAD BAD idea. Do your distillation inside a fume hood or outside!!
NOx- Nitric fumes are DEADLY DEADLY... your lungs will pack up in seconds and you'll die a horiffic death.

I nearly died this way many many years ago... never ever do a distillation of Nitric acid in an enclosed environment!

[Edited on 31-12-2005 by kABOOM!]




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[*] posted on 31-12-2005 at 08:34


>I nearly died this way many many years ago...

Really? Do you have any chronic health problems as a result?
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[*] posted on 31-12-2005 at 12:49


I was lucky to escape serious perminent injury. I suffered some damage to my lungs as a result of Nitric fumes--it took the better part of 2 months to get a clean bill of health. It was much like having a bad lung infection and every breath hurt. I'm 100% better now. Very little scaring--nothing that will cause serious problems in the future. I'm REALLY lucky...the doc told me that many people suffer long lasting health effects due to errosion of the lung tissues. So far so good...I learned my lesson.



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[*] posted on 1-1-2006 at 07:17


I have to agree with Rouge that the setup is less-than-perfect, using larger (and shorter) glass tubes and a vertical condenser might improve the output.
I have distilled strong (95% +) nitric acid with wery little discoloration under atmospheric tressure, so vacuum is not nessecery. I used equal parts (by volume) of 65% nitric acid and 98% sulphuric acid and got pretty much the expected yield (half the volume of the 65% NA). The setup was a 1l EM-beaker with taper joint, a vigareux-coloumn (probably not required), a three-way adapter and a fairly simple double-walled condenser.
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[*] posted on 1-1-2006 at 16:24


Yea, we learned that that setup had some serious problems. For one, the rubber stoppers dissolved and filled our condenser with a thick stopper gel... We got that cleaned up though. So, I suppose in time we will do it again differently.

How important in temperature control in this synthesis? We heated the H2SO4 up to 100 C then added the KNO3 and let it go from there without additional heating. We have no way of measuring the temp inside the vessel without taking the stopper off, so we are pretty much guessing and hoping that the temp stays in the 100-120 range.


[Edited on 2-1-2006 by Cyroxos]




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[*] posted on 1-1-2006 at 17:14


Having never distilled the azeotropic acid, only the fuming, I used a waterbath at around 80C for a nice slow distillation.

That also explains why you did not get any distillate last time, you did not heat it, only relied on the initial H2SO4 temperature. Seeing as you don't seem to mind getting the red acid, just use a boiling water bath heated by whatever your heatsource is and by also heeding the suggestions above you should definatly get product.

[Edited on 2-1-2006 by rogue chemist]




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[*] posted on 1-1-2006 at 17:30


How do you calculate the density of your final product? How do you know if you have 70% or 100%?



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