Emerald Green solution instead of yellow.

[artyfo61]

Good Morning,
This afternoon, I put about 36 grams of gold flake in a beaker with 400 ml of HCL, warmed it up, and added 100 ml of nitric acid. About 20 minutes later I added about 15 ml of nitric via pipette. Overall about every 20 minutes I added a total of 145 ml of nitric, the 45 via pipette. The reaction was going along fine and when the fumes ceased and the action ceased, I took the beaker off the heat to cool down. At this point I put in 3 drops of sulphuric acid and noticed there were just a few flakes of gold in the beaker. Rather than add acid, I took the flakes as an indication of solution saturation. I then filtered the solution thru a buchner funnel and was getting a nice, clear yellow solution. I transferred the solution to a new beaker, got my SMB out and added some water. When I poured it into the solution, WOW! I got a very fast black fizz that settled quickly and left me with a beahcker od crystal clear, green solution. Looked very pretty, but no gold and no idea where it went. What did I do wrong? Thank you for your help.

 

[FrugalRefiner]

It probably redissolved. You used way too much acid, especially the nitric. DeNOx with sultan if acid, then drop again.

Dave

 

[MvK]

Did you do a stannous test to see if gold was present before/after? Maybe the gold is still suspended in the acid and will drop overnight. But maybe its still in solution, stannous test is the way to tell.

If you dont want to do a stannous test you can always cement the PGM's out with copper.

 

[Shark]

DeNOx with sultan if acid, then drop again.

Sulfamic acid

 

[FrugalRefiner]

Thank you Shark. It's been a rough day.

Dave

 

[artyfo61]

It probably redissolved. You used way too much acid, especially the nitric. DeNOx with sultan if acid, then drop again.

Dave

Thank you for responding. I'll give it a try. How do you know how much HCL and HNO3 to use when putting gold into solution? I used a total of 400 ml HCL and 145 ml HNO3. That was a ratio of 2.75 HCL to 1 HNO3. Too much HNO3 acid but not that much. I still have 2 batches of 30g each of ram stick gold flake. I'm going to take another batch and try it again, but need to know how much of each to use. Thank you.

 

[Yggdrasil]

Thank you for responding. I'll give it a try. How do you know how much HCL and HNO3 to use when putting gold into solution? I used a total of 400 ml HCL and 145 ml HNO3. That was a ratio of 2.75 HCL to 1 HNO3. Too much HNO3 acid but not that much. I still have 2 batches of 30g each of ram stick gold flake. I'm going to take another batch and try it again, but need to know how much of each to use. Thank you.

Way too much.
You used enough Aqua Regia to dissolve 350g + of Gold.
Recommended use of AR here is like this:
Add enough HCl to cover your material, heat the solution carefully add some Nitric something like half the weight of your Gold in Nitric is a good start.
When the brown fumes dies down and the reaction slows add more half that again.
Then you continue by adding it with pipette some 3-5 ml at the time until there are no more reaction.
If the reaction stops before the material is gone, continue by adding some HCl and continue with Nitric the same way.

 

[kurtak]

but need to know how much of each to use.

As a "general" rule of thumb it takes about 1 ml of (67 - 70%) nitric (plus 4 ml HCl) to dissolve 1 gram of gold

I put the word about in bold print because just how much nitric it actually takes to dissolve 1 gram gold depends a great deal on the conditions under which the gold is being dissolved

Example of conditions; ----------

1) if you try to dissolve a solid 1 ozt bar of gold it will take MORE than 1 ml nitric to dissolve 1 gram gold

2) if you melt & pour that same 1 ozt bar of gold to shot/corn flake it will take much closer (plus/minus a bit) the 1 ml nitric to dissolve a gram of gold

3) if you are dissolving something like gold foils or gold powder it will likely take LESS then 1 ml nitric to dissolve 1 gram of gold

There are other factors (conditions) that play into just how much nitric it takes (more or less) to dissolve a gram of gold - the above are just examples of how the "condition of the gold" it self can change the amount of nitric needed to dissolve a gram of gold

I still have 2 batches of 30g each of ram stick gold flake

For 30 grams of foils you want 120 mil HCl --- than at most - 30 ml nitric (67 - 70%) & likely even less then that

Personally - I would start with no more then 20 ml nitric & then start adding a few drops of nitric at a time IF (the BIG IF) the 20 ml did not dissolve all the gold

In other words - even 20 ml can be MORE then enough (for gold foils) - depending on OTHER condition

I put about 36 grams of gold flake in a beaker with 400 ml of HCL, warmed it up, and added 100 ml of nitric acid.

Per the bold print - if you are using 67 -70 % nitric --- you used WAY TO MUCH nitric in the first place - for 36 grams of gold - at most you should have only needed 36 ml nitric (& likely less)

The amount of HCl you want to start with --- multiply the grams of gold by 4 - that's the the HCl you need

Then for the nitric - figure about 1 ml per gram - BUT - start with LESS then that - like only 2/3 that - then if the 2/3 does not dissolve all the gold - start adding nitric a few drops (2 - 3) at a time

Make sure the nitric is completely done reacting with the gold before adding more nitric AND after each addition

Kurt

 

[artyfo61]

As a "general" rule of thumb it takes about 1 ml of (67 - 70%) nitric (plus 4 ml HCl) to dissolve 1 gram of gold

I put the word about in bold print because just how much nitric it actually takes to dissolve 1 gram gold depends a great deal on the conditions under which the gold is being dissolved

Example of conditions; ----------

1) if you try to dissolve a solid 1 ozt bar of gold it will take MORE than 1 ml nitric to dissolve 1 gram gold

2) if you melt & pour that same 1 ozt bar of gold to shot/corn flake it will take much closer (plus/minus a bit) the 1 ml nitric to dissolve a gram of gold

3) if you are dissolving something like gold foils or gold powder it will likely take LESS then 1 ml nitric to dissolve 1 gram of gold

There are other factors (conditions) that play into just how much nitric it takes (more or less) to dissolve a gram of gold - the above are just examples of how the "condition of the gold" it self can change the amount of nitric needed to dissolve a gram of gold


For 30 grams of foils you want 120 mil HCl --- than at most - 30 ml nitric (67 - 70%) & likely even less then that

Personally - I would start with no more then 20 ml nitric & then start adding a few drops of nitric at a time IF (the BIG IF) the 20 ml did not dissolve all the gold

In other words - even 20 ml can be MORE then enough (for gold foils) - depending on OTHER condition


Per the bold print - if you are using 67 -70 % nitric --- you used WAY TO MUCH nitric in the first place - for 36 grams of gold - at most you should have only needed 36 ml nitric (& likely less)

The amount of HCl you want to start with --- multiply the grams of gold by 4 - that's the the HCl you need

Then for the nitric - figure about 1 ml per gram - BUT - start with LESS then that - like only 2/3 that - then if the 2/3 does not dissolve all the gold - start adding nitric a few drops (2 - 3) at a time

Make sure the nitric is completely done reacting with the gold before adding more nitric AND after each addition

Kurt

Great Info! Thank you very much.

 

[artyfo61]

Way too much.
You used enough Aqua Regia to dissolve 350g + of Gold.
Recommended use of AR here is like this:
Add enough HCl to cover your material, heat the solution carefully add some Nitric something like half the weight of your Gold in Nitric is a good start.
When the brown fumes dies down and the reaction slows add more half that again.
Then you continue by adding it with pipette some 3-5 ml at the time until there are no more reaction.
If the reaction stops before the material is gone, continue by adding some HCl and continue with Nitric the same way.

Thanks for your help. Will follow your recipe.

Edited by moderator, removed double quote.

 

[billgold]

Please post here how you plan to handle your botched attempt - before you proceed any further.

 

[artyfo61]

It probably redissolved. You used way too much acid, especially the nitric. DeNOx with sultan if acid, then drop again.

Dave

It worked! Thank you. I got less gold than I expected, but I think I add SMB to soon and didn't let it sit over night. But I did get some gold. Thanks.

 

[FrugalRefiner]

You can recover any "losses" in the stock pot. You never really lose any gold unless you throw it away.

Dave