gold inquarting with copper

[cheekyjass]

hi guys
I have some wires made of 35% gold and rest is copper so i was wondering if the refining process would be similar as in gold inqarting only i need to use copper instead of silver this time as the base metal and if yes how do i extract copper from the nitric acid to use the acid again
also after percipitaing gold with sodium metabisulphate can i reuse that aqua regia
thanks

 

[4metals]

If the wire is an alloy of 35% gold and the balance copper you should be able to digest it in 50% nitric acid. The gold will not go into solution and it will remain in the reaction vessel. From there it can be rinsed and digested in aqua regia to clean it up further. If the wires are gold over copper and the metals are not alloyed, the wires will have to be melted before you proceed.

As far as recovering the copper from the spent nitric acid, raise the pH to 2 with soda ash and add iron to drop the copper.

 

[Harold_V]

hi guys
I have some wires made of 35% gold and rest is copper so i was wondering if the refining process would be similar as in gold inqarting only i need to use copper instead of silver this time as the base metal and if yes how do i extract copper from the nitric acid to use the acid again

Unless your choice is to dissolve the material directly in AR, it doesn't matter if you use silver, and, in fact, that would be my choice. It uses far less nitric when digested.

If your wire is an alloy, you can process with nitric without altering the content. Removing the copper will be slow business, but it will happen, assuming you heat the nitric.

As far as reclaiming the acid, it doesn't exactly work that way. While you can reverse the process and reclaim the solution, I'm of the opinion that it makes no sense from an economical standpoint. You'd remove the copper, using scrap steel, then discard the solution.

also after percipitaing gold with sodium metabisulphate can i reuse that aqua regia

I'm not sure why you'd want to----and, it is no longer AR---it has undergone changes and is now just a chloride solution. Recycling such a solution would be akin to taking a bath in muddy water.

Harold

 

[cheekyjass]

thanks for reply guys and sorry i didnt mention that it is actually an alloy, so if i have got it correctly u guys mean that i dont have to melt this and add more copper to it to make it 25% gold and can put it straight into nitic acid (50%) to dissolve copper. There is a liitle problem though i have already bought nitric acid which 69% would that be alright and how much acid would i require if i have 100grams of this alloy.
thanks

 

[4metals]

The nitric you have is fine, by 50% nitric I meant take your nitric and cut it 50% with distilled water, as in cut in in half so you will have roughly 35% acid.

You should require around 600 ml of acid to do the job, add 500 and keep adding as the reaction slows until the reaction stops. No sense over adding.

The gold will be on the bottom. It will probably be 99% pure, you will have to aqua regia refine it to get a higher purity.

 

[cheekyjass]

so if for 100gms of 35% gold that has 65gms copper i need 600ml acid which means for every gram of copper i need around 9ml well thats a lot isn't it cos at another website called Goldnscrap.com i read u only need 2.5 ml of acid for each gram of base metal.
thanks

 

[stihl88]

Each material must be handled differently

It takes approx 3.98 mL of 70% HNO3 per gram of copper.

&

It takes approx 1.17 mL of 70% HNO3 and 1.17 ml of 100% H20 per gram of silver.

Edit: This was taken from Lasersteves thread here> http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=562&p=4766&hilit=+solution+until+it+becomes+saturated+with+copper+#p4766

Lazersteve wrote:
Nitric with Copper
The key equation for copper from wiki (Wiki Copper Nitrate) is:
Equation (1) :
Cu + 4 HNO3 → Cu(NO3)2 + 2 H2O + 2 NO2

Copper (Cu) has an atomic mass of 63.55 grams per mole

70% Nitric acid has 15.8 moles per liter of nitric acid (HNO3).

Using the ratios from the equation above:
15.8 / 4 = 3.95

Therefore 1 liter of 70% HNO3 is enough HNO3 to dissolve 3.95 times the mass of copper in equation(1):

3.95 x 63.55g =~ 251 g ( 3.98 mL of 70% HNO3 per gram of copper)

Nitric with SilverThe key equation for silver from wiki (Wiki Silver Nitrate) is:

Equation (2):
Ag + 2 HNO3 → AgNO3 + NO2 + H2O

Silver (Ag) has an atomic mass of 107.9 grams per mole

70% Nitric acid has 15.8 moles per liter of nitric acid (HNO3).

Using the ratios from the equation above:
15.8 / 2 = 7.9

Therefore 1 liter of 70% HNO3 is enough HNO3 to dissolve 7.9 times the mass of silver in equation(2):

7.9 x 107.9g =~ 852.4 g (1.17 mL of 70% HNO3 per gram of silver)

The above numbers are the theoretical figures, in practice you will find that you can get more life out of your nitric by :

a. Adding an water to the reaction.
b. Covering the reaction vessel with condenser or watch glass (reflux).
c. Capturing the NOx (mixed nitrogen oxides) off gases.
d. Recycling the nitrate by products of the reaction.


You can use the examples above to determine the amount of nitric required to dissolve any metal by substituting the appropriate equation and molar mass of the metal into the formulas given. Please note that nitric will not attack all base metals, and even passivates some and their alloys

 

[cheekyjass]

wow 8) that is some information thanks a lot mate.

 

[Harold_V]

The gold will be on the bottom. It will probably be 99% pure, you will have to aqua regia refine it to get a higher purity.

It also will be unlikely to have lost its form. With gold content that high, the end result is a very heavy honeycomb of gold---that is slow to give up its copper content. I had a similar experience with some 40% gold/copper wire. It took hours to remove the copper, but it did work, and quite well.

It is important that the wire not have a heavy cross section. If it's too heavy, you'll reach a point where the gold honeycomb isolates the balance of the wire from the nitric solution, stopping dissolution. To your advantage, the material will still dissolve in AR, unlike wire that is alloyed with excessive silver.

Harold