# mixed acid?



## ssharktu17 (Jan 29, 2022)

I have free access to an acid that is 32% phosphoric 42% nitric would it be possible to use something like this for dissolving and separating out silver?


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## butcher (Jan 29, 2022)

I would distill off the nitric acid from the phosphoric acid, bubbling the gas through some water with a little 3% H2O2, keeping the volume of the cold water in the tall receiver down as low as possible.
Crushed ice in a tall receiver with the hose gassing small bubbles to give the gas bubbles more time to saturate into the solution to acidify the nitric acidic water,.
With the goal not to dilute the product too much further, where it would be about right for dissolving silver, then can concentrate the dilute nitric to 68% azeotropic solution with the evaporation of the excess H2O from the acid if needed for aqua regia...


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## ssharktu17 (Jan 29, 2022)

butcher said:


> I would distill off the nitric acid from the phosphoric acid, bubbling the gas through some water with a little 3% H2O2, keeping the volume of the cold water in the tall receiver down as low as possible.
> Crushed ice in a tall receiver with the hose gassing small bubbles to give the gas bubbles more time to saturate into the solution to acidify the nitric acidic water,.
> With the goal not to dilute the product too much further, where it would be about right for dissolving silver, then can concentrate the dilute nitric to 68% azeotropic solution with the evaporation of the excess H2O from the acid if needed for aqua regia...


Excellent I need to do some more research into this distillation process and setup but this might be the way!


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## orvi (Jan 29, 2022)

butcher said:


> I would distill off the nitric acid from the phosphoric acid, bubbling the gas through some water with a little 3% H2O2, keeping the volume of the cold water in the tall receiver down as low as possible.
> Crushed ice in a tall receiver with the hose gassing small bubbles to give the gas bubbles more time to saturate into the solution to acidify the nitric acidic water,.
> With the goal not to dilute the product too much further, where it would be about right for dissolving silver, then can concentrate the dilute nitric to 68% azeotropic solution with the evaporation of the excess H2O from the acid if needed for aqua regia...


Why not just simply distill the nitric from the phosphoric acid ? I assume that after first distillation, you can add some water to the phosphoric acid residue and redistill to squeeze the last bit of nitric acid out ? 

Intended gas bubbler... Is meant to scrub the NO2 formed from decomposition of nitric ?
Just clarifying it in my head


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## butcher (Jan 30, 2022)

You could with fraction distillation although you would lose the nitric oxide invisible part of the insoluble NOx gas

NOx gases from distilling. bubbling through the cold oxygenated water.
Nitrogen dioxide gas dissolves in water, making nitric acid and insoluble nitric oxide gas.
3NO2 + H2O --> 2HNO3 + NO
or the nitrogen dioxide gas dissolves in water to form nitric and nitrous acids.
2NO2 + H2O --> HNO3 + HNO2
Nitric oxide (part of NOX gases) was produced originally through the distillation of the original reaction or in the reactions above.
Nitric oxide which is insoluble in water, the oxygenated water (hydrogen peroxide) can convert it to nitrogen dioxide gas which is then soluble in that water as shown in the above reaction
NO + O2 --> NO2
2NO2 + H2O --> HNO2 + HNO3


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## orvi (Feb 9, 2022)

Yeah, I see the point. Completely makes sense 
It would be nice to have some pressure adsorption column/bubbler, connected to pump for concentrated oxygen from oxygen concentrator. Difficult to assemble with low budget.
I did produced some nitric in my early days of refining from Cu/ammonium nitrate/HCl, bubbling to water or 30% H2O2. Difference between H2O and H2O2 was clearly obvious


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