Products of Lead(II) nitrate decomposition

It is known, that decomposition of Lead(II) nitrate is one of the ways of generating $\ce{NO2}$ for lab use. 


I recently did this in order to acquire $\ce{NO2}$ in liquid form (ambient temperature was ~0 °C), and got quite strange results. First, liquid $\ce{NO2}$ had 2 visible layers, usual brown one at the top and transparent at the bottom:


![enter image description here](https://i.stack.imgur.com/fLM0I.jpg)


Also, during condensation liquid initially had green color (I know that Graham condenser is not safe in this configuration - I wouldn't see this color change in conventional condenser setup).


![enter image description here](https://i.stack.imgur.com/G94lm.jpg)


Can anyone clarify why I got such variety of products instead of pure $\ce{NO2}$?




Check if the green condensate is $\ce{N2O3}$. [It has been reported to be blue-green.](http://nitrogen.atomistry.com/nitrogen_trioxide.html)


In the presence of water vapor and oxygen, the nitrogen dioxide that you are trying to obtain is in equilibrium with nitric acid and nitrogen trioxide, as explained [here](http://nitrogen.atomistry.com/nitrogen_tetroxide.html).


As reported in the Journal of Industrial and Engineering Chemistry, volume 12, number 6, page 531-538 (1920), condensation of gaseous nitrogen dioxide in a spiral condensor at -5 °C in the presence of oxygen and water vapor resulted in liquid with distinct upper and lower layers, the upper layer being a concentrated nitric acid layer (essentially no water) and the lower layer being a diluted nitric acid layer (27 %) water.


So the reason you are getting side products is likely that water vapor and oxygen are also present and causing equilibrium reactions that yield nitric acid, nitrous acid and nitrogen trioxide.


**Reference**


1. CCXIV.—The dissociation of gaseous nitrogen trioxide, Bernard Mouat Jones, J. Chem. Soc., Trans., **1914**, 105, 2310-2322, DOI: [10.1039/CT9140502310](https://pubs.rsc.org/en/content/articlelanding/1914/ct/ct9140502310/unauth#!divAbstract)


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The colorless area may be [$\ce{N2O4}$](https://en.wikipedia.org/wiki/Dinitrogen_tetroxide) which is in equilibrium with $\ce{NO2}$. $\ce{N2O4}$ is colorless and has a greater density and therefore is found at the bottom and green compound might be $\ce{N2O3}$ which is in equilibrium with $\ce{NO2}$ and $\ce{NO}$.


[![enter image description here](https://i.stack.imgur.com/1vfwX.jpg)](https://i.stack.imgur.com/1vfwX.jpg)


**Edit** :  

Boiling point of $\ce{N2O4}$ is 21.69 °C, so the temperature at which you perform experiment is also critical. Moreover, there is high probability that $\ce{N2O4}$ might be present in liquid state too.


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