I'm colour blind need help (pink)

[Harold_V]

Aww, not as much fun without the gas.
I am with GSP on this one. I think red heat may have been too much with these pins.

Assuming such items are processed with the dilute nitric acid method, how much heat is used isn't a factor. Process all of the ash that results from incineration and there will be no losses.

If incinerated pins are sent to the stripping cell, any values lost to the ash would have to be recovered by processing the ash. That's just good refining practice, so I fail to see any reason to be overly concerned about the temperature of incinerations, so long as the items are not melted.

I fully expect that there would be no migration of gold to the base metal, as virtually all gold plated objects used in the electronics industry, today, have a nickel barrier that prevents migration of gold to the base metal, which would melt long before the barrier achieved melting temperature.

My money says incinerate. Just don't discard the ash.

Harold

 

[Anonymous]

Guys why is everyone assuming that I don't agree with incinerating?

I do, in its place and time so would you all kindly stop assuming that I'm completely stupid? :evil: Just because I asked a question ? :lol: :lol:

 

[Harold_V]

Guys why is everyone assuming that I don't agree with incinerating?

If you don't wish to have a shot across your bow, don't make inflammatory remarks on the board. They will be rebutted in kind, as you're about to see.
Maybe it's because of the less that stellar comment you made previously:
"I don't profess to know everything about every process and one thing I have noticed in my time here is that everyone has slightly differing opinions on many processes and the steps within them. There are other ways to remove any residual HCl as opposed to incinerating so there was some validity to my question."

I do, in its place and time so would you all kindly stop assuming that I'm completely stupid? :evil: Just because I asked a question ? :lol: :lol:

I gather, from your comment, that you'll pick and choose what you think is the appropriate time to choose incineration, with no regard to what is considered acceptable by others.

You make it pretty hard to not think of you as a fool when you utter comments such as I quoted.
One of the things that gets my attention is anyone who comes to this forum and thinks themselves clever, posting comments that tend to be less than acceptable, in particular, for those who come here to learn. The one, above, is a classic example. It's as if you're trying to lend credence to your less than proper understanding of refining procedures, which makes it difficult, if not impossible, for the new guy to know what is and what isn't considered good procedure.

If you're familiar with a process that equals incineration in the way of eliminating one acid before introducing another, by all means, make it known to all of the readers. If, on the other hand, you do not, please refrain from posting such comments, as they tend to lead to mass confusion for folks who hope to learn acceptable processes.

You might understand that I'm less than impressed with anyone who professes to have "slightly differing opinions" where refining is concerned. There are processes that are known to yield acceptable results. Follow those processes until you are completely comfortable with refining, and you'll achieve the desired results. Get creative and arbitrarily disregard parts of any of the processes will most likely lead to less than acceptable results.

So, my friend, I reject your notion that there are "differing opinions" as to processing. Those who assume that they are clever and arbitrarily make changes are generally the ones who fail in their quest, then they can't understand why.

Harold

 

[kurtak]

If you're familiar with a process that equals incineration in the way of eliminating one acid before introducing another, by all means, make it known to all of the readers. If, on the other hand, you do not, please refrain from posting such comments, as they tend to lead to mass confusion for folks who hope to learn acceptable processes.

Harold

Correct as underlined above - which is why I asked Jon (spaceships) to share this info - simply telling me there is another way tells me nothing

Three years ago when I first came to this forum I read these 4 words that stuck in my mind - "incineration is your friend" --- after reading those words I paid close attention to the instructions I read concerning the How - When & Why of incineration

Having put those instructions of how - when & why into practice has proven those 4 words to be words of wisdom by a marked & noticed improvement in my refining outcome

Harold - I want to thank you for posting those 4 words - because I learned something from them - I learned that incineration is not just another step in the process but in fact - "incineration is my friend"

Kurt

 

[goldsilverpro]

On electronics, the nominal thickness of a nickel migration barrier, between gold plating and copper, is only 50 micro". At 50 micro", the nickel plating will be somewhat porous. This link says that, if the service temp is greater than about 250F, both the nickel and gold thicknesses should be increased and pure gold plating should be used. Migration rate is proportional to the temperature. I don't know how hot he got those pins, but it was probably somewhere between 1200 and 2000F. At the higher temp range, I can easily see the Ni/Au, and/or, Cu/Ni, alloying somewhat (check phase diagram) and the nickel barrier between Au and Cu completely broken down.
http://www.te.com/documentation/whitepapers/pdf/aurulrep.pdf

I've always used incineration for all types of jewelry sweeps, filings, and buffing dust. In that case, of course, it's a necessity. I've never used it in any part of karat gold refining and have never seen it done in any of the many refineries I've worked for or visited. I can see some merit in it, however, although I can't recall an instance in my refining life where it would have made any difference. I've always prided myself in being able to get all the of the gold and getting it pure, and was easily able to do that without incineration.

Pins are a different story. I think incineration of pins is a very bad idea. You probably end up with a mixture of Au, Au/Ni, Ni, Au/Cu, Cu/Ni/Au, Cu, and who knows what all and, to me, that just complicates a very simple thing. Several times over the years, I have taken pins from incinerated boards, refined them, and compared the results with the same pins that had not been incinerated. The incinerated pins always ran less and much less with cyanide stripping, my usual method of choice. I also remember dissolving some in AR, analyzing the solution on an AA, and they still ran a little less.

I've probably processed more pins than everyone else on the forum combined, although 4metals may be an exception. We often got 55 gal steel drums nearly full of nothing but pins, sometimes by the pickup load. They all were clean enough to directly process without incineration. A little soil won't hurt. If I were to get some pins packed in axle grease, I probably would use some chemical to clean them. Incineration would be my last choice.

 

[Geo]

On electronics, the nominal thickness of a nickel migration barrier, between gold plating and copper, is only 50 micro". At 50 micro", the nickel plating will be somewhat porous. This link says that, if the service temp is greater than about 250F.

Being the devils advocate here, the 250F was for an extended period. Long term usage may take more thickness than a short, very hot temperature. Is there any literature on the upper limits of the barrier failing due to increasing temperature and at what temperature it was when it failed.

 

[goldsilverpro]

On electronics, the nominal thickness of a nickel migration barrier, between gold plating and copper, is only 50 micro". At 50 micro", the nickel plating will be somewhat porous. This link says that, if the service temp is greater than about 250F.

Being the devils advocate here, the 250F was for an extended period. Long term usage may take more thickness than a short, very hot temperature. Is there any literature on the upper limits of the barrier failing due to increasing temperature and at what temperature it was when it failed.

I know of nothing in the literature. All nickel plating is not the same. This is mainly due to the myriad of different proprietary plating bath formulations available from the many manufacturers. All nickel solutions are doped with several proprietary organic additives (almost every manufacturer has their own, different, mix) to improve things like brightness and stress and to prevent things like pitting. These additives alter the grain structure differently, which would likely affect a lot of its particular properties.

I would imagine that the migration rate is geometric in its relationship to temperature. The rate would be much more than 2000/250 = 8 times the rate at 250F. It might be 100's of times faster. Also, after looking at all the phase diagrams, I feel that there could be some alloying between the metals. Also, as I said earlier, the very thin nickel is, at least, slightly porous. Also, all 3 metals are intimately attached to one another and the Au and Ni are super thin. The Ni is thicker but it would still take 20,000 sheets of it stacked up to make an inch.

 

[Geo]

Great, so now we have the how and the where. All we are missing is the why and that's easy enough to fix for the future, don't incinerate using a torch. 8)

 

[4metals]

I think the differences of opinion that are emerging here are because we have two distinctly different types of refiners here. I can only comment from a perspective of a commercial refiner and generally GSP is commenting from the same perspective.

I have worked in, owned, and designed for clients refineries with large incineration capacity, large stripping capabilities, and large digestion capabilities. In addition I am a strong advocate of analytical chemistry. When I set up a refinery I always stress the importance of an analytical lab. Not only to assay for settlement, to determine quantitatively the effectiveness of a process. A good analytical lab is essential to complete and cost effective processing.

I have also stripped large lots of pins without incineration. My quick and dirty quantifier was to splash some water on the scrap. If the water beaded up the parts were roasted before processing. There is a world of difference between roasting and incinerating.

Here on the forum we have refiners that have a lab consisting of a hood and a torch. For them, there is no such thing as roasting a lot before processing. For a larger well equipped refinery that routinely handles a wide variety of scrap for refining there are more, and much more effective, options.

This thread is about a type of scrap that didn't even exist when Hoke wrote her book. Her book deals very well with jewelers sweeps, sink sludges and karat gold. Her descriptions for processing are spot on, sweeps are incinerated and there simply isn't much possibility of over incinerating it. And karat gold is rarely incinerated (with the possible exception of old gold filled which is nasty from body oils) and even then the material behaves best if melted into a homogeneous mixture and granulated for acid treatment. Unfortunately we cannot carry over all of Hokes suggestions to all of the scrap types discussed here on the forum.

If you are refining in a small lab and your idea of incineration involves a torch and a frying pan, incineration in this case is likely to give you some insolubles that require reprocessing. That is a difference between a smaller refiner and a larger refiner. A small refiner processes your material and pays on out turn. (as in everything that does not come out as fine gold using your processing method is not paid on and essentially becomes eventual profit) A larger refiner generally processes material to a point where it can be sampled and paid on assay, with the possible exception of large lots of strippable goods such as drums of pins.

There are many roads to a cost effective end in refining. The more of these roads your refinery can take, the more effective your process can be.

 

[nickvc]

Like 4metals and GSP I have run a refinery and while I can see the need to find a route for the small home refiner there are methods and processes that work outside that which we all promote. The processes we all try to get people to follow work but become cumbersome in a production environment, workarounds exist which those that do process volumes use and find easier to reach the final goal. Volumes of materials present their own problems which need addressing to remain competetive within the business, not all these processes are suitable for the home refiner or hobbyist, the use of good assays and the ability to check the process is essential to ensure decent recovery of the values whilst pushing the materials through to keep your customer happy.
Modern recovery and refining isn't really like carat scrap refining the metals involved complicate the processes that our good friend Hoke promotes but her teachings still have value to allow all to follow the chemistry involved in the newer processes and why they work.
None of us know it all, there are many clever amateur and professional chemists here on the forum but I challenge all of the forum to claim they know better than anyone else, I learn virtually every day here and probably always will, different approaches aren't always wrong, sometimes a new view of an old process yields a better idea.
This is a science and by its nature it will evolve, not always in the way we predict or expect, remain open to new ideas, but always challenge dangerous processes or ideas and demand proof of the claims of successes or the chemical reasoning behind it.

 

[g_axelsson]

Playing the physics advocate here... :mrgreen:
Diffusion rates of solids in solids seems to follow exponential rates and as far as I can see approximately a tenfold increase in speed for every 100 degrees C increase in temperature.
So by raising the temperature from room temperature to 700 C (red glowing) we increase the diffusion rate 10.000.000 times.
That means 10 minutes of red glowing gives the same diffusion as 20 years at 120 C ( 250 F ).

This is an approximate calculation based on what numbers I could find in a short search on the net and could be really wrong. What I found was a diagram of diffusion constants for an alloy of 0-100% nickel with gold and the temperature dependent of diffusion rates for a number of non ferrous metals.

We will have some gold diffusing into the nickel and probably forming a colloidal solution of gold when the nickel is dissolved in acid but that should go through the filter and wash out with the fluids, not leaving such a lot of red sediments.

I'm starting to suspect litharge, lead oxide. It would have formed from the solder when it was incinerated the first time, although that would have been dissolved in the following HCl bath. It could also be some kind of iron oxide.
A couple of easy tests should bring a bit of clarity at least...
1. Take a small sample and put a drop of sulfuric acid on the pink residue. If it is colloidal gold it would not change color. As far as I can see litharge or lead oxide is reacting with strong acids and the sulfuric acid would turn it into white lead sulphate.
2. Take a small sample and put a couple of drops of HCl and a drop of HNO₃ to form aqua regia. If the red material is colloidal gold it would dissolve in the acid, and you should be able to test it with stannous chloride.

Göran

 

[ferrous]

Today test proved that it was colloidal gold
I was able to recover the gold
High heat for an extended time was the cause,
I learn from my mistakes and I'm glad I didn't do a large
Batch , today I did another 50gm test batch lightly heated pins with propane touch
The pins had transmission oil on them, washed with water and soap rinsed well
Proceeded with hcl to remove all the solder, 50/50 nitric to remove base metal
Now I have nice clean foils

Thanks a lot for the help
Junior