Help needed-Fingers.

[paulo123]

Hi there. I have almost 500 grams of gold fingers , I have taken the gold
flakes from the plastics and cut of the wires with a opperation knive-side cutter , so these 500 grams have no plastics-fiber and they only need to be put to the acids and I need to know :
How much hydrogen peroxide and muriatic acid is needed for a batch of 100 grams of gold flakes.

paulo123

 

[lazersteve]

PaulO123,

Cover the foils with HCl then add 25% of that volume in 3% peroxide. If you do not see a color change to blue-green in 20 minutes add another 50% of the first volume of 3% peroxide again. The foils should all float freely when the solution is swirled within 48 hours.


Steve

 

[goldsilverpro]

For a liter of solution, you have 800ml of HCl and 200 ml of 3% H2O2. If it doesn't start, add 100 ml more H2O2 for a total of 300 ml. So, with 30% H2O2, you would add 20 ml and 10 ml? Does the stronger H2O2 take less time, due to the HCl solution being stronger?

Does the H2O2 only jumpstart the reaction, until enough copper chloride is produced? Could you start the dissolution using copper chloride from a past batch, and no H2O2. If so, how much would you add to 800ml of HCl.

What is the weight of copper that can be dissolved in 800 ml of HCl?

 

[lazersteve]

So, with 30% H2O2, you would add 20 ml and 10 ml?

Yes.

Does the stronger H2O2 take less time, due to the HCl solution being stronger?

Yes, but you also run the risk of dissolving some of the foils if the peroxide is not diluted enough by the bath before it reaches the foils.

Does the H2O2 only jumpstart the reaction, until enough copper chloride is produced?

Yes. Air can be used instead of H2O2 which will be slower to form the required initial CuCl2, but will insure that no gold gets dissolved.

Could you start the dissolution using copper chloride from a past batch, and no H2O2. If so, how much would you add to 800ml of HCl.

Yes.

The optimal molarity of the bath is 3 M for maximum etch rate and minimal HCl fumes. Since 32% HCl is 10 M, you can add 333 mL of 32% HCl to 667 mL of CuCl2 and water. This should form a CuCl2 solution that is approximately 3M HCl.

If you want to use 800mL of HCl then you will add:

800/333 = 2.4

2.4 * 667 mL = 1600.8 mL of CuCl2 solution.

What is the weight of copper that can be dissolved in 800 ml of HCl?

The HCl is consumed as the CuCl is rejuvenated back to reactive CuCl2 via :

2HCl + 2CuCl + O (from Air) → 2CuCl2 + H2O

and metallic Copper is dissolved via :

CuCl2 + Cu (s) → 2CuCl

So the net result for 8 Moles of HCl (ie 800 mL 32% HCl)

at 1 Mole of HCl per mole of Cu dissolved is 8 moles of Cu or :

8 x 63.5 = 508 g

in pounds we have:

508 / 454 = ~1.12 pounds of copper

Hopefully I haven't made any mathematical errors, but if I have please feel free to correct me.

Edit :Corrected atomic mass of Copper.

Steve

 

[goldsilverpro]

Good, Steve.