That's right. Nitrogen oxides are an unavoidable byproduct of the process. That is why I indicated that the process must be done either outside or under a proper fume hood (or good forced air ventilation of some kind). I will add that if you are doing it outside then make sure to stay upwind lol.lazersteve said:Your rig looks like it would make a lot of NOx vapors in the area where the reaction is run. The reason I say this is because your collection flask and condenser do not have a good seal with one another. When I distill nitric acid using the chemicals you suggest, I get a clear to yellow liquid, with red vapors in the condenser, especially near the end point of the reaction.
It is best to use an all glass setup as I indicated. The reason is for preventing unwanted reactions. Also, I prefer to use lab quality or cooking quality borosilicate glassware which has very low thermal expansion so there is less chance of the glass breaking due to thermal shock.lazersteve said:I use a laboratory grade rig with blown glass Pyrex and ground glass joints to prevent this gas from escaping. I use a one liter flask for my reaction vessel and a 500 mL collection flask. If my joints on the rig are not tight (I use Teflon tape to seal them), I get red vapors emitting from the collection end of the rig towards the end of the reaction.
That is certainly one way to go. Turn the collector into a second condenser. However, I am not worried about the oxide gases escaping. Actually, I prefer not to further contaminate the distillate with the decomposing nitrogen oxides. However, I understand that there may be a process to further purify the nitric acid by exposing the end product to a bubbling vacuum of some kind but I have not looked into it. Your vacuum collection vessel may indeed provide that additional purification step. The HNO3 that escapes as vapor is very little so I am not inclined to complicate the distillation setup. Maybe I will try an enclosed collection system sometime and see what I get but the process I outlined works extremely satisfactory for me.lazersteve said:How do you contain the red vapors exiting the condenser? I would recommend that anyone who wants to distill their own nitric acid to use a closed connection to the collection flask with a salt water and ice cube bath on the outside of the collection flask. I use a vacuum flask for my collection vessel. Additionally, if you run the reaction under a vacuum, your acid will distill over at a lower temperature. By cooling the collection flask, you ensure the acid vapors are properly condensed and collected in the collection flask.
I considered that but It doesn't seem like it would throw off the calculations that much with the sulfuric acid being 98% concentration and the sodium nitrate being 99.2+% concentration. I will have to go over my calculations a few more times and see if I can spot errors that I might have made, which is very possible.lazersteve said:Your numbers may be off on you calculations due to the concentration of your sulfuric acid and/or your nitrate purity/water content.
Steve
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