Is the solution boiling

[wheed]

Good Morning all.

I am learning, so please be kind.

I am running a small batch of what was tooth gold (about 10 grams).

History. Broke out the teeth bone from gold via hammer. I then melted the tooth into a button. repeated for some other teeth I had. I then placed the button into a solution of HCl and Nitric (1:4 ratio) per Hoke and then more detailed in the forum books. I understood by not granulating the button it would take a LONG time to get the gold into solution (surface area low compared to granulating). Initially the button bubbled. I waited, and waited... The button developed a crusty exterior look to it. I knew I still had unspent Nitric in solution (because there was still a button left) so I added one more tooth button. Lots of bubbles again, then bubbles slowed. I then added another tooth button... More bubbles, and then bubbles slowed again. I then added heat to the HCl + Nitric + Water solution (water added because nothing was happening until I did add the water). All the buttons bubbled and danced in the bottom of the flask.

Question. I added heat slowly. As heat was added, the buttons started to dance a bit in the bottom of the flask. When I removed heat, bubbles stoped. Am I boiling the buttons in Acid, or are the bubbles just part of the reaction and/or the gold going into solution?

Question 2 similar to Q1. My math per forum books says the first button should of totally dissolved into solution, but I added more buttons because of low surface area to increase surface area with the end goal of getting as saturated a solution as possible before next step (precipitation with SMB). I now have a flask with some spongey buttons in the bottom. I know there is more gold than can be dissolved with Nitric + HCl. But I don't know if I have used up all the Nitric because when I heat the solution, the buttons dance an bubble. Am I just boiling acid, or is gold going into solution at higher temperature? Does warm/hot HCl + Nitric dissolve more gold than cold solution? Or is the purpose of adding heat to solution to increase speed of reaction? Can a warm solution of HCl + Nitric hold more gold than a cold solution? Chemistry was so long ago, and silly me sold the chemistry books after I passed the class.

My proposed plan to move forward...
1. Verify if all the Nitric in the solution is used up. Please nudge me in the right direction to do this please.
2. Pour solution and buttons through filter into a beaker and precipitate the gold out with SMB + Water.
3. Now that I have my ultra awsome mini furnace from Lazer Steve, melt the spongy buttons into a button again, and then pour into a bucket of water for granulation purposed.
4. Process the granulated gold which should go into solution much faster.

Definition of granulating to me is pouring molten metal into water bucket, correct me if I am using wrong words please.

Note, I have read Hoke, and the Forum books (which have a few bad links btw). I know I made a wrong turn trying to take an entire button into solution without granulating. Please don't hold it against me

Thanks in advance for any help, and thanks for all the help so far!

 

[Palladium]

Note, I have read Hoke, and the Forum books (which have a few bad links btw).

Could you post the bad links or tell me which ones and i'lll fix them for you.

 

[maynman1751]

Do a search on inquarting (proper term). The gold isn't just melted and poured into shot. The total gold percentage should be reduced with silver and then poured as shot (or cornflakes).
Also, I don't think that it's advisable to digest entire materials together. You should first remove the silver in Nitric before dissolving the leftover gold sponge in AR.
I think you need to do more reading and understand the process before proceeding. Just my opinion!

 

[philddreamer]

I think you need to do more reading and understand the process before proceeding. Just my opinion! Do a search on inquarting (proper term).

I agree with Maynman. There're many details to the whole process, & if you miss one, you could end up with problems. For example, if you just melt the metals in your inquart, but you don't stir properly with a hard graphite rod, you'll end up with a problem. If you digest the inquart in AR, (HCl+nitric) you'll run into another problem.

You can do some reading here:
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=12732&p=127126&hilit=inquarting#p127126

Take care and be safe!

Phil

 

[dcorley001]

Did you use 4 parts hcl and 1 part nitric or 4 parts nitric and 1 part hcl. From your description it sounded like the ratio was reversed..

 

[butcher]

wheed,

You have been given good advice, I suggest putting a hold on the project, and doing more homework, it sounds like you have learned some of the details, but are missing many parts of the processes, Along with reading Hoke's book, You can learn a lot about the dental gold and processes from reading Harold’s posts on this subject, the Platinum groups involved you can also learn much from Lou's posts, and Laser Steve’s posts, Stefan's (garage chemist) dental gold experiment is also very helpful, (flagged under the PGM section of the forum).

It is better to prepare yourself before attempting a process, by studying, than it is trying to figure out what went wrong and where you lost all of your values by just trying something your not sure about, especially when working with high value scrap.

 

[wheed]

Did you use 4 parts hcl and 1 part nitric or 4 parts nitric and 1 part hcl. From your description it sounded like the ratio was reversed..

I used 4 part HCl, 1 part Nitric.

The first button was 9.3 grams of near 24k gold. I estimated it was 23-24k because the test kit indicated it was greater than 22k gold.

The math I ended up with was...
288.3mL HCl + 74.4mL Nitric should have disolved the 9.3 grams of gold.

Why inquart if it is such a high percentage of gold? Inquarting I thought was for 14k(ish) gold?

Palladium. I had issues with the links to older posts. I am sorry I did not keep track of which ones didn't work. I will keep better track in the future and pass on the broken links to you next time I run into them. My computer is not located next to the fume hood in the garage, I have printed each of the forum handbooks and Hoke out and placed in a big binder, or what I call my gold refining bible. I like to put sticky tabs on the useful posts/chapters/interesting stuff. But to guide you to where I have issues with the book... Forum book #1 I like the most because rather than links to posts or videos, everything is cut and pasted into one document. Forum book 2 has links to stuff, and the links that worked, and where printable, ended up in my gold bible. So all I can say is I like the books that have cut and pasted stuff vs. links. I will keep track of broken links and PM to you if I find more.

You have been given good advice, I suggest putting a hold on the project, and doing more homework, it sounds like you have learned some of the details, but are missing many parts of the processes, Along with reading Hoke's book, You can learn a lot about the dental gold and processes from reading Harold’s posts on this subject, the Platinum groups involved you can also learn much from Lou's posts, and Laser Steve’s posts, Stefan's (garage chemist) dental gold experiment is also very helpful, (flagged under the PGM section of the forum).

It is better to prepare yourself before attempting a process, by studying, than it is trying to figure out what went wrong and where you lost all of your values by just trying something your not sure about, especially when working with high value scrap.

I have been on hold for a few weeks reading and searching for answers to my questions. I finally broke down and posted this morning because I keep collecting scrap and need to keep things moving through the process.

So the questions still stand I believe...

Question. I added heat slowly. As heat was added, the buttons started to dance a bit in the bottom of the flask. When I removed heat, bubbles and dancing stoped. Am I boiling the buttons in Acid, or are the bubbles just part of the reaction and/or the gold going into solution?

Question 2 similar to Q1. My math per forum books says the first 9.3gram button should of totally dissolved into the AR solution, but I added more buttons because of low surface area to increase surface area with the end goal of getting as saturated a solution as possible before next step (precipitation with SMB). I now have a flask with some spongey buttons in the bottom. I know there is more gold than can be dissolved with Nitric + HCl. But I don't know if I have used up all the Nitric because when I heat the solution, the buttons dance an bubble. Am I just boiling acid, or is gold going into solution at higher temperature? Does warm/hot HCl + Nitric dissolve more gold than cold solution? Or is the purpose of adding heat to solution to increase speed of reaction? Can a warm solution of HCl + Nitric hold more gold than a cold solution? Chemistry was so long ago, and silly me sold the chemistry books after I passed the class.

Thanks again, I hope the additional information will help achieve the answers to questions above.

 

[butcher]

The reasons I would in-quarter the gold with silver, even if the dental gold tested High for karat gold,

(It could be the karat is not as high as your test indicated, the PGM do not dissolve easily in test solution),

The PGMs may show high karat in the scratch test for gold, Platinum will not dissolve easily in aqua regia, (or in the scratch test with the test solution).

In-quartering with silver helps not only to separate the metals in nitric solution, but silver can be a collector of the PGM, and can help make it easier to dissolve them in solution, which can be retrieved in the electrolytic cell, silver can help the PGM's go into solution,(actually I use more silver than needed to quarter the gold, when messing with dental gold, ten time’s silver content in the Platinum group will help them dissolve into solution, the gold is left as powder, but I do not mind, just give it more time to settle).

Your question, of if heat is used to speed reactions (yes it is), and the question if solutions will hold more metal salts hot than cold (yes again), platinum needs a hot aqua regia solution to dissolve, so heating is needed here, (I would normally add a little water to help keep my acid in solution to dissolve metals instead of just vaporizing off), a watch glass and not too hot so your just boiling away your valuable metals in fumes.

 

[nickvc]

The guys have pointed out why your having problems and the correct approach to rectify the situation. The problem with going direct to AR is you have no idea of what base metals and other values are usually in the mix, the big refiners do go direct to AR but they use assays or these days xrf readings to check that the mix will dissolve and easily, we home refiners and small time refiners don't have that luxury. Dental alloys can be a nightmare to process directly in AR due to the mix of values and base metals so inquarting the metals with silver is almost mandatory and as butcher says excess silver will do little harm if there are quantities of PGMs as they will help dissolve them in the nitric and be easily recovered by cementation and then via the silver cell, the other problems your encountering could well be similar in nature to trying to dissolve karat alloys with high silver content in AR, a shell forms that is impervious to the acids. You state you have other values coming in so if I was in your situation I'd mix them altogether unless you suspect very high PGM content in the teeth using iquartation so any PGMs will report with the silver and be recoverable via the cell later, this at least gets your gold back out and leaves the other values to be sorted at a time your better aquatinted with their proper processes.

 

[qst42know]

A 9.3 gram button whole is going to be a slow dissolve indeed. Include platinum group metals will slow it even more.
Adding more buttons does nothing to speed this up. Pound the button thin with a clean hammer or melt and pour into water to form small pieces will.

There is a slight difference between the bubbles from boiling and the bubbles of dissolving. Lower the heat until the bubbles come only from the pieces of gold should be just about right.

Be patient a 9.3 gram piece will take several hours.

 

[wheed]

Thank You!!!

I now see the importance of inquarting, even if the test kit says high gold content.

Off to research if the sterling silver spoons I have found at garage sales will be good enough for quartering with.

You all rock, thanks again!

 

[butcher]

Sterling is great to use, that way you remove most of the copper from the silver in the same process.

 

[Harold_V]

Thank You!!!

I now see the importance of inquarting, even if the test kit says high gold content.

Off to research if the sterling silver spoons I have found at garage sales will be good enough for quartering with.

You all rock, thanks again!

The thing that is very important when you use AR to dissolve gold alloys is the percentage of silver that is present. From your description, I venture to guess that the gold you tried to dissolve slowly formed a crust that was somewhat gray/green in color, correct? That would be when action ceased, even after heating.

That gray/green color you saw (assuming you did) is a crust of silver chloride that is so dense that it isolates the alloy from the acid. Once you've created that situation, you can boil the material for days on end and not dissolve anything. Inquartation and a preliminary digest in dilute nitric acid is pretty much mandatory for this type of alloy, unless you can atomize the material. In that case, it can be dissolved directly in AR, before the hard crust of silver chloride can form. That is most likely beyond your capability. Do not try just granulating---that won't work.

Harold