Just began processing small gold pins (low grade) - help please

[Ellias]

Hello everyone!

I just began processing pin (very small amount to give my plan a go)

Equipment (safety is accounted for)
1. Hotplate
2. Sodium nirate
3. 32% HCL
4. Distilled water
5. Stannous test

my plan was to just use poor mans aqua regia to dissolve twice however maybe i should have given a HCL bath first to remove more base metals. I wanted to stop because there were a few unknowns.

steps i did:
1.Mix of 125 ml hcl 32%
2. 28 g NaNO3
3. 100 ml H20
4. Add my pins
5. After my reaction stopped i ended up with gold floating on top and some gold on pins.
6. Did a stannous test and no gold in solution.

Questions:

1.should I do another poorman aqua regia run after decanting and filtering?

2. What is the white powder at the bottom?

3. My stannous chloride is light blue - it cannot be palladium or silver can it?

 

[adam mizer]

The solution is pregnant with copper chloride falling out.
If you add HCL the chloride should go back into solution.
Filter this solution out and save foils.
Do your poor mans again.
Its possible you may have to do a few times. Lots of copper to be removed.

 

[Shark]

I will answer this the wrong way, but the way you ask for.

1. Maybe

2. Most likely the remnants from an excess of sodium nitrate.

3. Not likely.

Now, let’s try another way.

How many pins did you use for the volume of poormans AR you made up? Pins are largely base metals and requires a lot more volume of AR to take it into solution than pure gold will.

How hot did you heat it? Sodium nitrate needs a fairly high heat to produce actual AR. It works, but not exactly like using nitric acid. Not enough heat and the results maybe very little of anything will dissolve. Too much and you still have large amounts of excess salts from the nitrate.

Stannous test in base metals are not exact. This makes it harder to determine what you really have in solution. Is there any reason that the pins would contain silver or palladium?

 

[Ellias]

I will answer this the wrong way, but the way you ask for.

1. Maybe

2. Most likely the remnants from an excess of sodium nitrate.

3. Not likely.

Now, let’s try another way.

How many pins did you use for the volume of poormans AR you made up? Pins are largely base metals and requires a lot more volume of AR to take it into solution than pure gold will.

How hot did you heat it? Sodium nitrate needs a fairly high heat to produce actual AR. It works, but not exactly like using nitric acid. Not enough heat and the results maybe very little of anything will dissolve. Too much and you still have large amounts of excess salts from the nitrate.

Stannous test in base metals are not exact. This makes it harder to determine what you really have in solution. Is there any reason that the pins would contain silver or palladium?

1. I used around 85 grams of pins
2. The heat applied was around 100 - 105 Celsius. Before adding the Pins the color was dark yellow/ orange color with absolutly no salts left.
3. The pins i took from any connectors (maybe there were brushes of silver on them?)

I wanted to see and test if i could do this without an HCL bath or Nitric bath to save money and resources.

 

[Shark]

For the volume of AR made up for the volume of pins was a bit shy of enough. While hot it would hold things in solution but not when cold. So some parts dropped back out and others plated out. This can be seen on the pins as the color of copper. While running small volumes of pins directly in AR works pretty well, it changes some as the mass of pins goes up.

HCl will only hold so much volume of metals. Adding water, to a certain degree, can cause more to go into solution, but not stay based on temperature. By adding a nitrate salt to make AR, this volume has to be taken into account as well. If we put the pins into solution with HCl, say the form of AP, we need a given volume to hold those metals as well. The same volume required with the AR. This leaves little or no advantage as to resources saved of chemicals. It does save some headache by allowing gold to be dropped from a cleaner AR solution. The gold can refined a in a much smaller volume once base metals are gone. Meaning a much smaller volume of AR and less drag down of base metals.
Now if we put pins directly to AR the biggest savings are in time. We now have a tiny bit less waste to deal with, in exchange for longer times washing the powders, more chemicals to do the washes with as well. And still volumes of waste to treat or dispose of.

Time versus costs.

Let’s look at your 85 grams of pins and not get technically scientific about it. I like 2L beakers so add them to the beaker, cover with HCl then double that. Add sodium nitrate and 1/2 the volume of he HCl in the form of water to it. Heat to 150-175F. Hotter is ok, just don’t crazy with it. Let it work. If it doesn’t all dissolve added the proportions of chemicals but in smaller volumes until it does. All this is only good if you’re willing to work with very dirty solutions. It is also slower to settle and may need filtering of the gold powders and not waiting for them to settle on their own. It can vary based on certain metals involved. It can also affect what precipitants are used. Heavy copper in volumes in poormans AR can also cause a situation where the copper can become the oxidizer and continually dissolve you gold over and over.

Will it work, yes. Does it require less chemicals, not really. Will it save time, sometimes. Was it worth it for me try it and find out for myself, yes. Do I still do it, sometimes.
What ever you decide, hope this helps a little.

 

[Ellias]

For the volume of AR made up for the volume of pins was a bit shy of enough. While hot it would hold things in solution but not when cold. So some parts dropped back out and others plated out. This can be seen on the pins as the color of copper. While running small volumes of pins directly in AR works pretty well, it changes some as the mass of pins goes up.

HCl will only hold so much volume of metals. Adding water, to a certain degree, can cause more to go into solution, but not stay based on temperature. By adding a nitrate salt to make AR, this volume has to be taken into account as well. If we put the pins into solution with HCl, say the form of AP, we need a given volume to hold those metals as well. The same volume required with the AR. This leaves little or no advantage as to resources saved of chemicals. It does save some headache by allowing gold to be dropped from a cleaner AR solution. The gold can refined a in a much smaller volume once base metals are gone. Meaning a much smaller volume of AR and less drag down of base metals.
Now if we put pins directly to AR the biggest savings are in time. We now have a tiny bit less waste to deal with, in exchange for longer times washing the powders, more chemicals to do the washes with as well. And still volumes of waste to treat or dispose of.

Time versus costs.

Let’s look at your 85 grams of pins and not get technically scientific about it. I like 2L beakers so add them to the beaker, cover with HCl then double that. Add sodium nitrate and 1/2 the volume of he HCl in the form of water to it. Heat to 150-175F. Hotter is ok, just don’t crazy with it. Let it work. If it doesn’t all dissolve added the proportions of chemicals but in smaller volumes until it does. All this is only good if you’re willing to work with very dirty solutions. It is also slower to settle and may need filtering of the gold powders and not waiting for them to settle on their own. It can vary based on certain metals involved. It can also affect what precipitants are used. Heavy copper in volumes in poormans AR can also cause a situation where the copper can become the oxidizer and continually dissolve you gold over and over.

Will it work, yes. Does it require less chemicals, not really. Will it save time, sometimes. Was it worth it for me try it and find out for myself, yes. Do I still do it, sometimes.
What ever you decide, hope this helps a little.

This helped a ton. Will be working on cleaning now! You guys are the best!

 

[Ellias]

Quick question if anyone knows. How bad would it be to add non gold bearing AR solution to my AP solution stockpot?

 

[Yggdrasil]

Quick question if anyone knows. How bad would it be to add non gold bearing AR solution to my AP solution stockpot?

One should keep the Nitric and Chloride based leaches separate.
AP is "never" waste.
As for the question, as long as the AR is active it can be used for treating pins and stuff you like to dissolve but don't like to use fresh acids on.

 

[kurtak]

2. What is the white powder at the bottom?

Two possibilities' - (1) copper chloride is precipitating out because not enough HCl/water was used to keep the copper in solution - so IF (the BIG IF) it is CuCl hot water should dissolve it & put the copper back in solution

2) it is meta stannic acid - the nasty tin paste created when tin reacts with nitrates (otherwise known as a refiners nightmare) - meta stannic acid will not dissolve in water &/or the other acids commonly used in refining (HCl, nitric or sulfuric)

So - when dissolving pins in acid with nitrates (nitric acid or other nitrates as a nitric substitute) the meta stannic acid can be created by two sources

1) if the pins had solder on them & the solder was not first removed with a HCl leaching the tin solder will turn into the meta stannic acid as a result of the nitrate in the poor mans AR

2) If the pins are made of bronze (an alloy of copper/tin) instead of copper or brass (brass being an alloy of copper/zinc) then the meta stannic acid will be created as a result of the nitrates in the PM (poor mans) AR reacting with the tin in the bronze alloy of the bronze pins

So if hot water does not dissolve the white powder away then more then likely it is meta stannic acid

Kurt

 

[Yggdrasil]

Two possibilities' - (1) copper chloride is precipitating out because not enough HCl/water was used to keep the copper in solution - so IF (the BIG IF) it is CuCl hot water should dissolve it & put the copper back in solution

2) it is meta stannic acid - the nasty tin paste created when tin reacts with nitrates (otherwise known as a refiners nightmare) - meta stannic acid will not dissolve in water &/or the other acids commonly used in refining (HCl, nitric or sulfuric)

So - when dissolving pins in acid with nitrates (nitric acid or other nitrates as a nitric substitute) the meta stannic acid can be created by two sources

1) if the pins had solder on them & the solder was not first removed with a HCl leaching the tin solder will turn into the meta stannic acid as a result of the nitrate in the poor mans AR

2) If the pins are made of bronze (an alloy of copper/tin) instead of copper or brass (brass being an alloy of copper/zinc) then the meta stannic acid will be created as a result of the nitrates in the PM (poor mans) AR reacting with the tin in the bronze alloy of the bronze pins

So if hot water does not dissolve the white powder away then more then likely it is meta stannic acid

Kurt

There is a member that has found that Metastannic acid dissolves in hot concentrated HCl.
Information from last week.

 

[kurtak]

There is a member that has found that Metastannic acid dissolves in hot concentrated HCl.
Information from last week.

Can you link me to that post/thread info

Kurt

 

[Yggdrasil]

Can you link me to that post/thread info

Kurt

Here it is:
https://goldrefiningforum.com/threads/problems-with-matastannic-acid.16047/post-374154