Question about the apparatus used. Is the red handled valve a vacuum line to draw fumes into the water or is it simply a water feed? Is the tube extending upward connected to the stopper on top of the bubble trap which functions as the exhaust path? Is the entire process driven by pressure generated by heating the reaction?
Yes, red valves are two water feeds, one for vacuum aspirator pump and second just a water to cooler (if needed to use). They aren´t connected in this setup. Whole setup is the simplest possible, driven just by slightly positive pressure of NOx gasses generated. I use this setup for small scale dissolutions - with intention to cut down corrosive NOx evolution into the fumehood.
And yes, glass tube extending upwards is connected to the ground glass stopper of the wash bottle. Yes, it is just exhaust from the wash bottle.
I have also bigger setup of similar construction, but much larger, with 6L big flask connected to bigger washbottle, but this time, also condenser is mounted on top to recover evaporated water/HCL back to the reaction - as it is used mainly for AR digestions.
I also performed few Ag material dissolutions in it, these times excluding wash bottle, adding ca 30 cm Vigreux column between flask and condenser. I then set steady dripping addition funnel with dH2O on top, which drops into the condenser, through the column back to the reaction - and reforms quite a bit HNO3 simultaneously reducing NOx outgas.
In even bigger digestion setup, I also added tube with oxygen inlet (from oxygen concentrator), which made use of nitric nearly catalytic (for the purpose of dissolution - as counteranion, there need to be stoichiometric ammount added through the dissolution).
costs practically nothing. With air inlet, you can get nearly complete absorption (conversion of NO to NO2 by the action of oxygen).
