SuperOxide
Hazard to Others
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Boiling point of 92% RFNA
I made some RFNA yesterday for the first time. From the literature I read online and the videos I watched I was expecting it to come over at 86 °C.
But to my surprise, almost all of it came over between 110-120 °C.
I know the azeotrope boils at 120 °C, but this absolutely wasn't the azeotrope. I am using 93% concentrated sulfuric acid, and the potassium nitrate
I was using was recrystallized and oven dried so I figured there couldn't be any water in there. And when I got it's density, it came in at 92%. It
also passed the obligatory nitrile glove test setting it on fire almost instantly.
Is there any reason it would be coming over at such a high temperature? I was thinking maybe the heating mantle was too high, but it was actually on
the lowest setting I could set it on (One of those Faithful 1L heating mantles).
P.S. Some references that I saw did actually say that RFNA boils at 120 °C (Wikipedia for example), but I figured those were either incorrect or just confusing it with the azeotrope. But now I'm not so sure.
[Edited on 7-3-2022 by SuperOxide]
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Fery
National Hazard
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If you heat a mixture of H2SO4 + KNO3 + HNO3 you must heat it to higher T to force HNO3 to distill so the vapor has higher T. Once you obtain HNO3 it
should redistill at literature b.p. as then you do not need to overheat the content in distillation flask anymore.
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SuperOxide
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Quote: Originally posted by Fery  | | If you heat a mixture of H2SO4 + KNO3 + HNO3 you must heat it to higher T to force HNO3 to distill so the vapor has higher T. Once you obtain HNO3 it
should redistill at literature b.p. as then you do not need to overheat the content in distillation flask anymore. |
Ah, this clears things up.
Thanks!
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draculic acid69
International Hazard
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Quick question: have U calibrated your thermometer? Using a standard
glass lab type I've had them read upto 11'c over the correct temperature.
Pic below is the typical type Im talking about :
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![[*]](images/xpblue/default_icon.gif){kind=icon}
