[iheartsludge]

Hello,

I am going to run an experiment but have found information on nitrous acid HNO2 limited.

Adding 1.6g NO2-/L solution under pH = 2.0 yields nitrous acid at a concentration of 92% HNO2 and 8% NO2- (from distribution diagram).

My application is under about 35psi pressure. I'm also concerned with atmospheric conditions.

It is known that nitrous acid comes out of solution and upon contacting atmosphere is rapidly decomposes to NOx (nasty brown gas).

So, in my sealed vessel, it exists HNO2, and upon release to atmosphere decomposes to NOx.

So, I am curious, at 35psi, what percentage of my HNO2 in solution and what exists as a gas? I figure I would need solubility of HNO2, which I don't have.

Any input is helpful.

Thanks!

[cheese (MSW)]

For information on Main Group Chem consult G&E:
N. N. Greenwood, A. Earnshaw, Chemistry of the Elements 2nd ed. (1997) p 459-460.
It appears from info given there that the rxn of HNO2 to give NO and NO2 only takes place in the gas phase.  Keeping your soln at 0 °C under N2 should be fine. When you say 35 psi what gas are you using, hopefully an inert gas like N2?  Carry out rxn in an RB flask (or small Carius tube) fitted with a Teflon valve.  Weigh out your 1.6 g NaNO2, evacuate flask and place under N2; cool in salt-ice and add cold HCl (N2 flush).  Warm to 0 °C and allow rxn to occur.  Freeze in liq N2 and do 2-3 freeze pump thaw cycles.  You now have your soln at 0°C under vac (0 psi).  Pressurize with 50 psi (35 + 15) and your soln is ready to go.  My guess is that at low T you won't get any tell-tale sign of brown NO2 and besides it is a closed container and will come to equilibrium. good luck!