October 25, 2020, 10:21:57 AM
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Topic: Setup for evaporating concentrated acids  (Read 935 times)

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Offline GeorgeSmith

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Setup for evaporating concentrated acids
« on: November 29, 2019, 07:17:12 AM »
So I will be performing plenty of acid leaches during my current project, which is followed by an evaporation step. The acids to be evaporated are aqua regia and concentrated HNO3, and volumes are 50-100 mL per occasion.

To prevent damage of the fume hood ducts, my supervisor suggests keeping a beaker of concentrated ammonia stirring in the fume hood to neutralise the acid vapours coming off the hot acid, and taping some wet pH paper inside to follow the process. To me, this sounds quite silly, and I would feel a lot more comfortable with a more proper setup. Say performing the evaporation in a round bottom flask or E-flask, and connecting a cooler and leading the condensate into a basic solution for neutralisation.

What do you guys think? Is the suggestion by my supervisor enough, or do you have any suggestions for a proper setup?

Online chenbeier

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Re: Setup for evaporating concentrated acids
« Reply #1 on: December 02, 2019, 03:23:29 PM »
To use the ammonia is silly, because the  fume hood will get a lot of nebula and precipitation of ammonium nitrate.
Your idea is better.

But a fume hood should be able to manage the NOx.

Offline Enthalpy

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Re: Setup for evaporating concentrated acids
« Reply #2 on: December 03, 2019, 10:32:45 AM »
Oops, I didn't react immediately... With ammonia, neutralisation would produce ammonium nitrate, which can detonate.

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