De-Noxxing AR

[Buzz]

Since i just ran out of Urea, i thought i'd try the "boiling off the Nitric" method of denoxxing AR.

Is there a way to know for sure when all the Nitric has been removed?

I'm currently getting no brown fumes (just white) and the whiff of "Red Death" has disappeared.

There has been no colour change to the AR either.

At what point do i stop the boiling and adding HCl?

Kind regards
Buzz

 

[Noxx]

You boil down your solution until you obtain a thick syrupy constancy.

You repeat this step three times.

 

[Buzz]

Thanks Noxx,

Do you add the HCl till you reach the original volume.

What i mean is, boil 500ml down to syrup and add HCl till it gets back to 500ml and boil down again...etc?

Kind regards
Buzz

 

[Harold_V]

Thanks Noxx,

Do you add the HCl till you reach the original volume.

What i mean is, boil 500ml down to syrup and add HCl till it gets back to 500ml and boil down again...etc?

Add just a small amount. If you have the temperature right, and the solution has been evaporated until it has changed color to a dark red, the moment you introduce the HCl you should see some brown fumes evolve. The boiling point is now above that of water, so you should see the solution boil a little in the process. Allow the added HCl to evaporate, then repeat. If, when you add HCl you don't get any brown fumes, you can assume you have eliminated the free nitric.

You can make your task a lot easier if you'll simply add a button of gold while you're evaporating. Instead of evaporating the nitric, you'll consume it by dissolving the gold button. It's faster, and insures you have completely eliminated free nitric. You must provide HCl in order for the nitric to do its work. Weigh the button before and after if you are concerned about how much gold you added to the process.

I used this method for years, and I never used urea.

Harold

 

[Buzz]

Thanks Harold,

I'm trying to get away from using Urea.

I have a small 10 gram button i could use too.

Kind regards
Buzz