Sciencemadness Discussion Board

Bubbling from nitrourea

night429 - 12-12-2020 at 20:11

I've attempted to make nitrourea on two occasions. In both of these, I follow the same general procedure:
  1. Using around 30mL of 93% sulfuric acid
  2. Cooling to at or less than 0°C
  3. Adding 8g of urea nitrate in small portions
  4. Stirring after additions and keeping the temperature under 0°C

In both procedures, I've had the same issue happen: Every time I add the urea nitrate, it starts to bubble quite a bit. This gas that's produced is acrid and smells similar to chlorine gas, but more sharp(?). It doesn't fume in air, either. I also don't get a precipitate upon crashing the sulfuric acid into ice water, which makes me think it's a result of the urea nitrate itself, and not a contamination.

I've looked for what this gas is, but I couldn't find anything descriptive. The little resources I've found about it only say that there are bubbles produced, but I've only found one that describes what the gas could be. It describes that nitrourea hydrolyzes to form nitroamide and isocyanic acid. Seeing as though my sulfuric acid is only 93%, this might have been a possibility. However, neither of these products match, either:

I'm really curious as to what this gas is, so if anyone has any information on this, I'm interesting in knowing.

Boffis - 13-12-2020 at 15:45

You always get a little bubbling from this reaction but it represents only a small part of the overal product that is decomposed. The gas is mainly nitrous oxide which is practically odourless, the smell you detect is probably the minute aerosol droplets of sulphuric acid dispersed by the bursting bubbles at the liquid surface. Just carry on and pour the finished reaction mixture into iced water and recover your product the de-gassing is a minor side reaction if you keep the temperature low.

night429 - 21-12-2020 at 20:54

Quote: Originally posted by Boffis  
You always get a little bubbling from this reaction but it represents only a small part of the overal product that is decomposed. The gas is mainly nitrous oxide which is practically odourless, the smell you detect is probably the minute aerosol droplets of sulphuric acid dispersed by the bursting bubbles at the liquid surface. Just carry on and pour the finished reaction mixture into iced water and recover your product the de-gassing is a minor side reaction if you keep the temperature low.


That makes sense, thank you so much!