# reverse aqua regia HNO3:HCl 3:1 or 4:1



## teclu (Sep 26, 2009)

What metals digest?, any link and information is welcome.

teclu


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## Anonymous (Sep 26, 2009)

Why reverse the ratios? you do not need anything close to that amount of nitric and it just makes more work to get rid of the excess.

Ratio should be something like 3 or 4 HCL and 1 HNO3 (or less)

Jim


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## teclu (Sep 26, 2009)

Jim hello,


....just wanted to know more about the combination of acids, 3 or 4 parts HNO3 70%(not dilute) and 1 part HCL 32%. 
eg. for Ni alloys, Fe alloys and Cr alloys


teclu


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## butcher (Sep 27, 2009)

I will not be too much help here but this is my idea on it.

Normally metals that will not disolve easily in as acid need an oxidizer, some metals will form a oxide layer protecting them from the acid you are trying to disolve it in, other metals are more nobel and the hydrogen in the acid can not attack them without the use of an oxidizer.

lets take gold here, gold too nobel for hydrogen to attack and to make a gold chloride salt with muratic acid (hydrochloric acid)(HCl), so we need an oxidizer, like HNO3 nitric acid, the nitric provides the oxidizer, so that the gold atom will loose an electron and disolve into solution as a salt of chloride in the solution.

the formula normally used for aqua regia 4 HCl to 1 HNO3, has been used because it is a very good combination of oxidizer to chlorine, enough oxidizer to do its job and enough chlorine to hold the gold as salts of the metal,

so with this the only reason I could think of as to having an lot more oxidizer in a solution would be to attack a metal that would passivate easily (oxidized layer protecting the metal from disloving in the acid), silver in a chloride solution would act this way, also lead in chloride, and other things like that. (afraid to say Etcetera).

down side of using too much oxidizer would be having to dissapate it later to get back your metals, and your acid concentration depending on temperature and concentration and other thing like that, the acid amount would hold less metals as salt, so less metals would disolve into solution.

and things like that.


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## arthur kierski (Sep 27, 2009)

this reverse ar is used to dissolve sulphides.specially copper concentrates------i used this sometimes when i have dificulties to dissolve some stuff-------als laboratories have many leaches processes and this is one of their processes


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## teclu (Sep 27, 2009)

Butcher , 
Sir, thank you for your quick involvement, very useful for me always!

Arthur Kierski,
Sir, same thanks!

Now:
I thought I use this formula for Au and Pd plated material which not dissolved in nitric(Fe, Ni, Cr,maybe kovar or similar alloys), after all are dissolved then cement on copper, then powder(AuPd)dissolved in 50/50 nitric for Pd, Au powder reprocessing in AR and Pd from nitrate solution for re-cementation on copper.
I already tried a sample and the results are satisfactory.
The material(pins) is without solder(tin, lead), i cut these.
2,56 ml HNO3 70% and 0,64 ml HCL 32% disolve 1gram of this type plated pins.
HNO3 undiluted, because if I use diluted it doubles the volume of solution. Pd dissolves in this combination(HNO3 70% un diluted).

teclu


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## goldsilverpro (Sep 28, 2009)

Most any combination of HNO3 and HCl will dissolve gold. I have used 10HNO3/1HCl/9H2O for certain applications.


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