Smelting fine carbon ash
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The essential FeSO4 will be arriving in days so I'll have days to read the materials. Guess I'll be ready.anachronism said:
I ash the carbon using a pot with heat underneath. A electric heating thing, I'll take a photo of it tomorrow.
I think it's very very likely that the carbon isn't completely ashed, since we didn't spend much effort examining this part.
This conversation has reminded me to ash the carbon tomorrow by myself, as this part had been done mostly by someone else. I will try the 'adding KNO3 when carbon is red hot' method which I found on this forum. Then I will smelt the ash again, see if there's a difference.
Sir, your reply has given me a lot of new knowledge. I'm not sure if it is, but I found a lot of white bubbles on the upper-inner part of the crucible, maybe that's KNO3, I don't know. But knowing that the graphite crucible would absorb KNO3, I guess I'll stop using it or find something else to replace it.snoman701 said:
Stirring the molten is the another thing I've missed out. Important too. I'll try this with a fire-proof gloves. Thanks!
I've noticed that a lot of Na2CO3 with little SiO2 would make a lot of bubbles. The flux almost spilled out of the crucible today as I was doing experiments. Didn't think of using this as an advantage though. Thank you for your experience talk, I will try that.
The borax/silica part, I assume you mean 2 part borax, 2 part silica, and 1 part soda ash? I always felt like silica would make the molten too sticky, and gold would stick to the slag, so I always put more soda ash than silica. Is this wrong?
I'm new to this. Actually I'm new to this whole industry, and I'm learning from XRF assaying to ores processing to now hydro-metallurgy and fire-assaying.snoman701 said:
I thought, graphite was the only option here because, I thought, it was how this 'induction furnace heating the crucible not the quartz cup protection very safe bla bla bla' thing works.
You suggesting SiC crucible and I asked my supplier and they did have it. I suppose in this way I could use KNO3 more effectively? If yes, I'm buying a box.
You can use SiC crucibles with induction, but 5 kw might be pushing it a bit. I've got 7.5 and the smallest SiC crucible barely gets hot enough for silver, on a good day. You end up dumping a lot of power in to the conductive crucible.
I found that the factor which affect me most was how well the carbon was ashed. Adding KNO3 during ashing when the carbon started to become red hot surely speeded up the process, but the carbon I was using was around 1-2mm large so only the surface of it ashed rapidly. Most part of the carbon was still not-burnt.
So, I started grinding the gold-bearing carbon, in order to get cleaner ash. I know there would be great loss of gold during grinding. I feel like the first step to find out the problem is to make sure it's not about ashing. Or, problem solved.
Will be updating my results tomorrow.
So, I started grinding the gold-bearing carbon, in order to get cleaner ash. I know there would be great loss of gold during grinding. I feel like the first step to find out the problem is to make sure it's not about ashing. Or, problem solved.
Will be updating my results tomorrow.
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I'm not certain why you would add acid during ashing.
What temperature and time are you taking and what equipment are you using?
What temperature and time are you taking and what equipment are you using?
Potassium nitrate may be acidic in a smelt, but I would not say it is an acid.
But yes, why add anything when ashing. I think he meant to use it as an oxidizer.
I had a high temperature "ashing" furnace made just for this type of work.
It was plumbed to were you could add pure oxygen during ashing of the sample.
But yes, why add anything when ashing. I think he meant to use it as an oxidizer.
I had a high temperature "ashing" furnace made just for this type of work.
It was plumbed to were you could add pure oxygen during ashing of the sample.
I found the problem, guys!
I used nitric acid to dissolve the copper button.
The residue was assayed by XRF.
It had almost 95% of the original gold value from ash.
To conclude, I did manage to condense all gold value into the copper button. It was the surface of copper button having low readings, now that I can assume the inner part of the button is more condensed with gold.
So it is now I understand that I failed the assaying because I missed out one procedure showed in our guidebook: I need to compress the oval-shape copper button into a form of plate. I guess this will force the inner part of the copper button show up.
I used nitric acid to dissolve the copper button.
The residue was assayed by XRF.
It had almost 95% of the original gold value from ash.
To conclude, I did manage to condense all gold value into the copper button. It was the surface of copper button having low readings, now that I can assume the inner part of the button is more condensed with gold.
So it is now I understand that I failed the assaying because I missed out one procedure showed in our guidebook: I need to compress the oval-shape copper button into a form of plate. I guess this will force the inner part of the copper button show up.
Is it possible that smelt button have different composition on surface and different in inner part. I heard that button have same composition through out. Can some one confirm Is it normal that button have different composotion at surface and different in inner part?
Depending on melt time, temperature and such parameters it may happen that the button can be poorly mixed.
I think.... maybe.
Like a solder operation if all metals do not melt properly, but more braze together.
But in normal conditions they should be more or less uniform, unless you have alloys that don't play well together.
The surface can have impurities from slags, oxides and such though.
Depends on what you are smelting. It is obvious when one look to the phase diagrams of metals which are melted. Some - like AgPd system has nice phase diagram without any eutectics (but that doesn´t mean it will stay homogenous after melting). Others, like Fe-C are much much different and difficult.
One of the most crucial things for preparing homogenous button is cooling time. If you left the bead to cool slowly, it has plenty of time to establish equilibriums and create various crystalline phases inside - which ultimately result in different composition eg on the surface and inside the button.
I had plenty of experience with this phenomena on PGM alloys. XRF was sometimes practically useless for assessing the composition... Also AgCu tend to alter the composition, despite being melted at higher temperature and poured into the mold.
kumbirai.mhere
Active member
What's the correct flux composition when smelting carbon ashes?
Fully ashed Carbon is usually leached in AR or similar.
Besides that, if you plan to smelt it I would believe some collector metal has to be used.
Do some searches on the forum for Carbon ashes.
