# Aqua Regia neutralization with Sodium Hydroxide



## Aberu_ (Feb 25, 2018)

Can you neutralize AR with dissolved gold using Sodium Hydroxide? I have already added some Urea, and I believe there is ammonium floating on top. It's foamy and doesn't dissipate when I stir the solution.


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## kernels (Feb 25, 2018)

You can neutralize an acid with a base, correct. 

But . . . I suspect this is not actually what you want to do. The term "neutralize" is used incorrectly when people talk about removing excess Nitric acid from a AR solution that now contains some dissolved precious metal.

Urea and Sulfamic acid are used to convert excess Nitric acid in solution before precipitating Gold. So, the question is, why do you want to neutralize AR with Sodium Hydroxide ?


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## Aberu_ (Feb 25, 2018)

kernels said:


> \The term "neutralize" is used incorrectly when people talk about removing excess Nitric acid from a AR solution that now contains some dissolved precious metal.



I thought Urea was added to stop the acid from redissolving the gold, and that Sodium Hydroxide would be better because its a stronger base.


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## kernels (Feb 25, 2018)

Sure, but you don't want to neutralize the HCl because you need that to react with the SMB to form SO2 to reduce the Gold to metallic particles. 

You don't really want to neutralize the solution, only get rid of the excess HNO3

Also, adding too much Sodium Hydroxide will likely drop your Gold and other metals in solution as their hydroxide salt. 

Really you want to be looking at Sulfamic acid, it converts the excess Nitric acid to Sulfuric acid which has the added benefit of precipitating any Lead in solution, this Lead can then be separated from the solution before precipitating the Gold.

Urea works too, but not as popular these days as Sulfamic acid.

If you have used urea, I don't see what the problem is, are you having trouble precipitating the Gold? At this point you probably will need to give more details if you want better answers.


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## Aberu_ (Feb 25, 2018)

kernels said:


> If you have used urea, I don't see what the problem is, are you having trouble precipitating the Gold? At this point you probably will need to give more details if you want better answers.



I thought that it might have been relevant, also thank you for the quick response! This was all I needed.


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## usesynergysen (Mar 30, 2020)

I think the question is HOW much urea do you add if you’re using a 4:1 ratio (aqua Regis) per ounce of product to be refined in order to remove the nitric then how much sodium hydroxide to drop the gold ....but can I just measure the oh because I believe their are different precious metals in my product....


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## anachronism (Mar 30, 2020)

You shouldn't be using 4:1 in the first place. 

For most applications you should be adding Nitric as required.


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## FrugalRefiner (Mar 30, 2020)

This thread doesn't make much sense.

First, usesynergysen are you also Aberu_?

If not, you both seem to be way off in what you're doing.

As Jon has said, you shouldn't use a set ratio of HCl to nitric for aqua regia. Use only as much nitric as needed to do the job. Then you don't have to destroy excess nitric.

Instead of urea, you should use sulfamic acid to destroy any excess nitric. Urea will cause you problems down the line.

Your question is impossible to answer. How much AR was used? How much metal was dissolved? What kind of metals? Was heat used? Was the reaction vessel covered or open to the atmosphere? These will all affect how much excess nitric there might be.

We don't use sodium hydroxide to drop gold. We use a selective reducing agent like ferrous sulfate, SMB, or other precipitant.

In other words, your questions show that you shouldn't be trying any of these processes yet. Put your mess away lightly covered in a safe place and start studying the forum until you understand the issues I've raised.

Dave


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## jason12 (Oct 17, 2020)

about sulfamic acid,why it is better than urea?and how much should i use?


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## sayf (Dec 17, 2020)

jason12 said:


> about sulfamic acid,why it is better than urea?and how much should i use?


urea can make a mess if used in the wrong way , its also dangerous and can be used as secondary explosive it also can explode if combined with nitric as urea nitrate and heated to high temperature , sulphamic acid is safer and when combined with nitric it forms sulfuric acid so increasing it may cause problems in your solution , you can tell when to stop adding sulfamic acid by adding an impure gold nugget to your solution , such a nugget will immediatly react with nitic acid during that reaction add sulphamic acid gradually to the solution and notice the nugget if it stops reacting with the solution then the nitric is dead if not then add more sulfamic and so on ...
u can simply replace the gold nugget with a copper nugget too


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## sayf (Dec 17, 2020)

your purpose is to get rid of the nitric acid because it prevents the gold precipitation , neutralizing the solution by a strong base such as NaOH will kill the nitric and the HCL together , in order to precipitate your gold you will need the HCL to be there so dont use a base because it will kill the innocent HCL 
using urea will sometimes cause a white fiaming layer above the silution , u can get rid of that by simply filtering the silution .....
regards


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## Emmanuel Tanzania (Mar 20, 2022)

Hello friends, this forum has helped me alot in my research on good extraction alot here in Tanzania. But i still can not get clean gold from my precipitate.

I droped gold from AR using baking soda and the precipitate was dark brown powder. I then heated the brown powder(dry) with charcoal to decompose the gold hydroxide powder then smelted it directly with a propane torch but the result was nothing close to gold though it looked metalic Brown black. 
Where have I gone wrong? Thanks


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## Yggdrasil (Mar 20, 2022)

I'm a bit surprised.
I can not recall any advice here on the forum to neutralize AR with alkalis.
Where did you find this procedure??
Definitely not drop it that way, it will drop most metals as hydroxides and you then have to redissolve to refine.
We try to use as little nitric as possible, then destroy the remaining nitric, if needed, with sulfamic acid.
Then we drop the gold with Sodium meta bisulfite (SMB), SO2, Oxalic acid, Ascorbic acid, Copperas among others.


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## Emmanuel Tanzania (Mar 21, 2022)

Thanks @ Yggdrasil. I read the method over the internet and tried it. Neutralisation helps when dealing with alot of solution (5 litres) leaching gold concentrates at room temperature. To give you a clear picture here is what i do:
Note: the ore I have here are gold sulphide ores.

1) I get concentrates from the sluice (from 1 ton of ore) which i clean up and then sock them in dilute nitric acid (1HNO3:3H2O) for 24 hours. Then i rise the solution.

2) after the pretreatment I prepare a solution of AR (2H20:3HCL:1HNO3) which is use to leach the pretreated ore at room temperature for 24hrs.

3) After testing for gold in solution I filter the pregnant solution then neutralise the solution with baking soda to form gold hyroxide powder. I then heat the hydroxide powder then smelt what is left of the powder.

Problem is I don't get clean gold, i get a reddish to black metal.


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## Yggdrasil (Mar 21, 2022)

First you should be thankful for still being alive, next you should realise that YouTube and the internet can kill people, there are a lot of dangerous information out there.

Of course you don't get clean gold, you are doing it all wrong. 
By neutralizing the solution you drop most metals in solution as hydroxides. 
Copper zinc iron arsenic what not.

If you use AR you have to do more or less as I said in the first post.

And of course if you did not manage to dissolve all the metals in the ore, a significant amount of the gold are still in the ore.

AR is not a solution for leaching ore, it is for refining after.
AR will dissolve and free all kind of toxic elements from what is in the ore.

For ore: Cyanide complexes, hypochlorites, thiocyanates or others are used based on the composition of the ore.
Often more than one method can be used in succession.

I'm not very proficient on what is best and not on ore, but there are some very good people in this forum.


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