Dental plate

Hi fellas,

Today I came across a dental plate and I am trying to find out if it's gold or not and if it contains any PGMs.

Here is a picture:



I tested the piece with 10k, 14k & 18k acid and the mark did not dissolve at all...

Now, I can hardly believe that is 18k gold but so white ! It also tested negative to silver and is non magnetic.

Finally, it weighs 10.5 grams.

What are the next steps to determine if it's really gold ? Is it possible that my acids are showing a false positive ?

as long as it's not plated... (i can't tell...)
i belive that knowing the density will help guide you further...

Does it bend easy? I think if it snaps it is usually not of value.
Did you heat it and see if it does not change color?

What jimdoc said. If it is brittle, and breaks when you attempt to bend a corner, it likely has no precious metals within. I say it does not.

Break off a tiny corner and heat in a test tube with a drop of AR. If the resulting solution is a dark green color, it's valueless. If, on the other hand, the solution is a dark brown color, it will contain platinum group metals.

In any case, allow the acid to work until it is exhausted, then note any changes of color of the solution. If it changes color, you are witnessing values being cemented by the remaining base metals.

Before discarding, be certain to test the solution with stannous chloride, early on, and after it has ceased working.

Harold

I'd almost bet its worth in platinum that it's not. I bet it's a high temp cobalt-nickel type alloy. If you take a torch to it and it turns a rainbow, it's not noble.

Thanks for the great tips !

I'll let ya know of the results.

Lou was right, definitely not gold.

Your tips greatly helped.

I've seen plenty of the crap.


Most high noble (platinum and palladium-containing) dental alloys I've encountered were all bronze looking.

Lou said:

I've seen plenty of the crap.
Most high noble (platinum and palladium-containing) dental alloys I've encountered were all bronze looking.

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Not all are, however. Many of the caps I encountered were platinum group metals. They tend to have a slightly less blue color than the high temperature alloys. It's very obvious when you see them together.

When I'd encounter a large mixed lot such as that, instead of taking a chance of tossing anything of value, after removing any traces of teeth, they got incinerated, then processed directly in AR. By using less than was needed, the AR would consume everything until it was exhausted, then the remaining base metals would cement the values. When the solution tested barren, it would be decanted, with a fresh start of AR applied. I would repeat that cycle until there was almost nothing left to dissolve, so the end solution was primarily of value. It's a great way to eliminate base metals when processing by nitric or other single acids fails to work.

Harold

Harold,

I understand exactly what you are doing here but wish to point out that unless one is proficient in using stannic acid losses are to be expected. I also would not recommend trying this with electronic scrap as there are better methods for that material.

Oz said:

I understand exactly what you are doing here but wish to point out that unless one is proficient in using stannic acid losses are to be expected. I also would not recommend trying this with electronic scrap as there are better methods for that material.

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I feel that learning how to be proficient with stannous chloride should be the top priority for anyone on the forum because, as Oz said, if you don't you'll lose values. It's easy to learn if you make up small amounts of various PM solutions and play with them - straight, mixed, diluted, strong, etc. Download the 2 Hoke books for instructions. I would imagine a jeweler would sell tiny amounts of Pt (and maybe other PGMs, if he had them) for little money. You can also intentionally contaminate small portions of these PM solutions with various base metals and see what happens (or, doesn't happen). The reaction colors can be easily recorded with a digital camera. If I were just starting out, this is what I would do.

If the value of the electronic scrap is high, say $200 - $300/pound, or more, I think aqua regia should be considered, at least for certain things. The method Harold detailed in the above post is an excellent way to do this. The beauty of it is that all the values end up in a relatively small amount of acid. I look at recovery and refining as a series of steps, where each step makes the pile containing the values smaller. That's exactly what this process does. Everyone should understand how and why it works. It not only is a good recovery method, it will explain why many of the member's solutions surprisingly test barren for gold.

Oz said:

Harold,

I understand exactly what you are doing here but wish to point out that unless one is proficient in using stannic acid losses are to be expected. I also would not recommend trying this with electronic scrap as there are better methods for that material.

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Your comments are in step with what I've said right along. AR should not be used as a recovery procedure in any but the rarest of exceptions. The reasons are many, loss being but one of them. To the inexperienced refiner, it's an open invitation for grief.

To that end, it would be interesting to know how many have posted on the forum, asking where their gold is. There is so much bad information floating around outside this forum that the world is turning out a huge number of badly directed people. Sad thing is, they want to believe it, because it sounds so simple. That's the nature of people, looking for a fast buck, instant success, and a free ride.

Refining successfully requires a person to do some home work, to expend a given amount of effort, and, most of all, to learn to trust experienced people. They can save one a ton of trouble and hard work. The problem, of course, is sorting those that know what they're talking about from those that don't.

With time, I have become somewhat less willing to help people that work without knowing. It is my opinion that anyone that attempts to refine and doesn't understand stannous chloride, or has NOT read Hoke, deserves all the problems they create. Knowledgeable people on this forum have made it dead easy to have stannous chloride, by making it from lead free solder. Others have made Hoke available at the click of a button. There is no excuse for not being informed.

Read Hoke, folks, and DO NOT WORK BLINDLY. Make standard solutions and test with stannous chloride. Do that until you know and understand the reactions. It is also a good idea to have a solution of DMG (dimethylglyoxime) at the ready, for those cases where one may wish to know if there is palladium in a mixed lot, or if the blue color you see is copper, or nickel. It's all in Hoke.

Harold

Harold_V said:

Your comments are in step with what I've said right along. AR should not be used as a recovery procedure in any but the rarest of exceptions. The reasons are many, loss being but one of them. To the inexperienced refiner, it's an open invitation for grief.

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The problems comes IMHO in the fact that if you search the internet that AR is the most frequently advised way to recover gold. How many other places list the procedures we use on this forum in such an open manner that they can be effectively used for recovery of PM's

To that end, it would be interesting to know how many have posted on the forum, asking where their gold is. There is so much bad information floating around outside this forum that the world is turning out a huge number of badly directed people. Sad thing is, they want to believe it, because it sounds so simple. That's the nature of people, looking for a fast buck, instant success, and a free ride.

Refining successfully requires a person to do some home work, to expend a given amount of effort, and, most of all, to learn to trust experienced people. They can save one a ton of trouble and hard work. The problem, of course, is sorting those that know what they're talking about from those that don't.

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More than just some home work Harold, it's like craming a 4 year college into 2 years of study. With no definative book to go by when you first enter the class until you are told hey get this book it will save your life, and by that time you are 1/4 of your way thru school and have to play catch up to the rest of the class.

And even at your age you should know by now that most people are not going to expend the given amount of energy that it takes to become successful at this or anything else in their lives. People want the shortest route to success. Much less listen to and or trust any one. You yourself must make ths decision to continue to teach these individuals or concentrate on the ones that listen and follow directions.

With time, I have become somewhat less willing to help people that work without knowing. It is my opinion that anyone that attempts to refine and doesn't understand stannous chloride, or has NOT read Hoke, deserves all the problems they create. Knowledgeable people on this forum have made it dead easy to have stannous chloride, by making it from lead free solder. Others have made Hoke available at the click of a button. There is no excuse for not being informed.

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But Harold, you have tought so many here on the forum that they can handle this process for you with new people.
There is no excuse for not being informed. I think the illness is called lazieness.

Read Hoke, folks, and DO NOT WORK BLINDLY. Make standard solutions and test with stannous chloride. Do that until you know and understand the reactions. It is also a good idea to have a solution of DMG (dimethylglyoxime) at the ready, for those cases where one may wish to know if there is palladium in a mixed lot, or if the blue color you see is copper, or nickel. It's all in Hoke.

Harold

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Harold you are one of the founding Gradfathers( I say that with a smile because of youe age :lol: ) of this forum. To see you be disheartened about trying to teach someone here is unnerving to say the least, to think that you might loose interest in this and stop teaching the correct way of doing things. Your teachings are blunt, but when you step in they need to be because of the health dangers involved in this industry.

How would you feel if you stopped posting for a while and came back to find out that one of the members had lost their life because of an accident involved in this field that you could have made a post on to stop it?

Everyone has to start out some where in this field as a beginner. Do you remember your first days at doing this work. Do you look back and remember the paitence that the individual that tought you had to stick with you because they saw some thing in you to stick with you and teach you. If there was an individual like that in your life I am sure you have never forgotten him/her and think about them on a regular basis for what they tought you.

Harold you are respected, honored, trusted & wanted by all here on the forum.

Sorry I didn't mean to hijack this thread. I'll put my dunce hat back on and go back to my corner now.

I stumbled upon that method that Harold talked about several years ago by sheer accident and stupidity. I had done a batch of gold fill in aqua regia and couldn't figure out what had happened to the gold that was not precipitating out of the mother liquor.
I finally figured out that the base metals had precipitated the gold after exhausting the ar. I dissolved the solids again in ar, that were leftover from the spent solution and there was the gold that I thought was lost.
I routinely use this method now for the types of scrap that gsp referred to and certain other scrap material. Done just the way Harold detailed , its a good way to recover and concentrate values. Keep in mind you still have to refine these values, there is a difference between recovery and refining.

Harold_V said:

... AR should not be used as a recovery procedure in any but the rarest of exceptions. The reasons are many, loss being but one of them. To the inexperienced refiner, it's an open invitation for grief....

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Would anyone care to expand on that thought? Why is AR wrong for primary recovery from cornflakes or other inquarted material?
It is almost impossible for many of us to obtain Nitric acid. So, the choices become:
AP, HCl/Cl and poor man's AR.
Why should people go through the hassle of making nitric when they can go straight to the process of completely digesting the metal in one step with AR? After the AR, the excess nitric is neutralized (or consumed with a timesaver button) and then the gold is dropped with SMB.

Inquarted gold is 75% or greater silver and will not dissolve in AR.

Instead a crust of silver chloride will form on the cornflakes and the alloy will not dissolve. Likewise AP, HCl-Cl and any other chlorine based solvents will form this protective layer and stop further action.

35% Nitric acid is the way to go with inquarted material.

If you want to use AR on alloyed gold, bring the alloy up to 18kt plus and cornflake the resulting alloy.

AR will work partially on extremely finely divided 10-18 karat gold. You will still have to deal with some of the gold being trapped in this silver chloride protective layer. This layer always requires more effort and processing to extract the last of the gold from the silver chloride residue.

When properly inquarted and extracted with nitric acid, you can be certain that you will get all the gold the first time through with minimal losses.

Steve

From when I started posting on this forum I've been slowly changing the way I approach any refining issue. I must admit, compared to some on this forum, I've been lucky. If I need nitric acid I have nitric available to me. When I was in business I had plenty of affordable nitric acid.

In the last week I've had some time so I decided to look at the world through the eyes of some others on the forum. Taking advantage of the cold weather I decided to whip up a gallon of nitric acid to see what some of you go through.

Well the acid came out pretty nice, clear and strong... in my opinion if I had to I could do without technical grade nitric. BUT THANK GOD I DON"T HAVE TO, it's a pain in the a** to make. Do you have any idea how much gold I could have processed in the time I was making the nitric?

My point is inquarting is nice, produces a nice base metal free gold sponge which refines easily in aqua regia and results in a high purity gold bar. I've done it for God knows how much gold in my day as I'm sure others here have. The catch was I always had cheap nitric on hand and never had to think twice about nitric usage.

I'll tell you now, having brewed my own nitric, if that were my only option I would do all of my refining in a way that used as little nitric as possible. For high yield gold foils or karat that would be in aqua regia. I'd keep the silver under 7.5% and run with aqua regia, reduce the chlorides from the AR to metallic silver, assay for retained gold if necessary, and recover the silver via silver cell, and process the slimes for gold and other PGM's.

Having home brewed my own nitric I can feel chemists' pain and would factor nitric availability into any refining scheme.

Indeed, distilling Nitric is pain in the neck. I used to do this but now I'd buy it instead...

Has anyone tried the potasium chloride method of disolving high silver gold in AR?

Noxx and Steve, thank you for feeling our pain.
Harold, as usual, is giving good advice and I appreciate your guidance.
O.k., so here is really weird question: if a person doesn't have access to nitric acid, could they use copper or another metal to inquart the gold and then process it directly in poor man's AR?
If silver is used as the inquarting material, then the AR will form AgCl2 in the AR and reduce the rate of dissolution, but copper will form a water-soluble copper chloride that will wash away and allow the AR to act on the gold. I understand that this process would have to continue until all of the metals reacted. If the process was stopped too soon, then the values would be cemented out of the solution by any unreacted copper.
Am I nuts?