My first gold drop

[Maurice]

Hi everyone,

I've been a member of this forum for a long time now. Been reading a lot, have done small scale tests and learned a lot. I've recently bought me some equipment and a few chemicals that I would need for my first real try at getting some gold. Got KNO3, H2SO4 37%, H2O2 3%, NaClO 2.5%, HCl 30%, SMB among others. I'll be using the AP and HCl + bleach for the resulting foils. All is done outside away from people and myself. I've gotten proper glasses, a breathing mask and a box of gloves.

Materials:
The materials that I used where RJ-45 Phone jacket pins. They are sturdy gold plated pins connected to a copper wire with a brass clamp to make the electrical connection. Was less then 50 grams in pins.

Process:
I dissolved the base metals with 30% HCl and 3% H2O2 (AP). Where is covered the material in HCl and added a small quantity of H2O2 at different intervals. When the solution became darker towards green I added an air hose and a fish tank bubbler and let it bubble for a couple of days till all that remained where gold foils.

I filtered the solution and used some HCL to rince a few times to get rid of the base metals.

I put the filter in a clean beaker and covered it in HCl and added small quantities of 2.5% bleach (NaClO) over time. After a couple of hours all the gold was dissolved and I poured the result through a filter, rinsing it with some water until all the color was gone from the filter. I ended up with about 500ml of yellow liquid. The color was fainter then the color of a solution of 1gram of gold per liter. So there is not that much gold in the solution.

I read that it might be more difficult to drop the gold if there is little dissolved. So I put the beaker on a hot plate and set it on a low heat to remove some excess liquid and get it down to about 250ml. I let it cool and settle overnight. This is the only time I've used heat in the process.

The next morning when looked I saw that there was some metal gold on top of the liquid and some at the bottom. Swirling the beaker showed a lot of sparkling tiny pieces of gold in the solution. Looks nice, but that is not what I would have expected to happen.

Somehow a part of my dissolved gold has come out of the solution when I reduced the volume by halve. Maybe some contamination happened where the gold has cemented out and the contamination went into the solution.

As a next step I plan on adding some HCl and some bleach to make sure all the gold is dissolve again, filter it and then add SMB to the solution to drop all the gold.

Questions:
Anyone might have an idea why part of the gold came out of the solution ?
Any improvements to the process I followed or things that I should do different ?

thank you for your time

 

[Maurice]

I've placed the beaker onto my hotplate again, set it to low heat.

Added about 50ml of HCl and about 10ml of NaClO 2.5% to the beaker and covered it with a watch-glass.

After an hour all the gold that dropped out has redissolved into the solution so I'm back to the situation where part of my gold dropped out .

I'll let the beaker cool down down now and pour the liquid through another filter to filter out any paper pulp that was not filtered out the last time. A few small pieces made it past my filter.

Then I'll pour it back to the beaker I used for dissolving the gold and I'll use SMB to drop the gold. I'll do a stannus test to make sure I got all the gold out of it.

Give the gold a few rinses with HCL and water and let the remaining water evaporate drying out the gold powder.

 

[Maurice]

The last filtering didn't go as planned. I see a few bits and pieces floating around this morning when I looked at the filtered result from yesterday. So this came through my Büchner funnel or it appeared overnight after filtering.

* edit: removed the image. I'm unable to add an image to the post as it keeps complaining that it can't determine the dimensions of the image. I know the url is correct http://theplace2be.nl/IMG_0407.JPG

I'm going to filter the solution once more but this time I'll be using a larger filter paper and using my glass funnel instead of my Büchner funnel. see if I can catch the white stuff on the bottom.

I do wonder what it might be. It could be residual paper from the filters used in the process or a byproduct from the HCl + bleach method for dissolving gold.

Anyone got an idea what it might be?

The solution has a little bit of a greenish tint to it, so I suspect there are still some base metals dissolved in the solution.

How to proceed from here ?

I could drop the gold from the solution using copper or I could drop the gold with SMB.
Once dropped I should do a few hcl and water washes to get rid of most conterminations before letting the powder dry.

 

[butcher]

Maurice,
Bleach is a basic solution or an alkali , opposite of an acid, when added to an acid it consume the acid, and will make salts out of that acid.

In this case the hydrochloric acid and hypchlorite solution form sodium chloride salt (table salt) and water and generate volatile chlorine gas that is the oxidant that dissolves the gold and other metals into solution.

2HCl + NaClO --> NaCl + Cl2 + H2O

Gold is oxidized by the chlorine gas in the solution.
2Au + 3Cl2 --> 2AuCl3

Gold in the acid with the hypochlorite solution produces a salt of sodium( sodium chloride) , a salt of gold (gold chloride) dissolved in a solution of water (along with salts of any of other metals involved in solution) ...

2Au +6HCl +3NaClO --> 2AuCl3 + 3NaCl + 3H2O

Once gold is dissolved we normally heat the solution just enough to drive the free chlorine from solution, letting it sit in the heat of the sun or using a heat source to drive off the volatile gas.

Evaporating the solution will saturate the solution with the white salts of sodium chloride which can begin to precipitate out when the water volume is not suffufient enough to hold all of the salts in solution...

Bleach consumes or converts the acid to salts while it is making chlorine gas, using too much bleach and not enough acid can make the solution neutural or even make the solution basic (no longer acidic)...

 

[Maurice]

Hello butcher.

Thank you for your time.

Once gold is dissolved we normally heat the solution just enough to drive the free chlorine from solution, letting it sit in the heat of the sun or using a heat source to drive off the volatile gas.

How do you know from observing the beaker that you drove of any remaining gas ?

Evaporating the solution will saturate the solution with the white salts of sodium chloride which can begin to precipitate out when the water volume is not sufficient enough to hold all of the salts in solution...

That's proberbly what happened. The volume in the beaker was 500ml and it had some white solids in the bottom. Thinking it was some residual filter paper pulp that got past the filtering. It should pose no issue and will be gone after a filtering. But instead of filter paper pulp it might just have been table salt that came out and evaporating it further drove other salts out from the solution aswel. Which is why I saw the sparking of very small gold partials.

Bleach consumes or converts the acid to salts while it is making chlorine gas, using too much bleach and not enough acid can make the solution neutral or even make the solution basic (no longer acidic)

I tested the solution and the PH is well below 7, so it is still acidic.

Might have been better to make a separate flash to generate the Cl gass and bubble it through the solution using a tube with a glass tube at the end. The table salt would not be in the gold solution but in the reaction flask instead. Although dealing with common salt should not pose an issue. I should be able to get rid of that with a few water washes.

I'll continue with dropping the gold from the solution with SMB testing with stannis to make sure I've got all the gold out of it and clean the gold afterwards.