# substituting bismuth for lead in fire assays



## 4metals (Apr 10, 2010)

I was wondering if anyone has substituted bismuth for lead in their assaying procedures? I had done fire assays, in side by side comparisons, in the late '90's when the concerns about lead pollution were getting more attention in the press and with the EPA and found it to be an effective substitute but its cost made it prohibitive.

Well the EPA is back and asking questions as to the disposal of used cupels from fire assaying so I sense there may be a renewed interest in the future. It's a shame to say but most assayers simply toss their used cupels in the trash and that behavior may soon be stopped. The only way to avoid the manifested collection of the cupels as a hazardous waste is to cupel with bismuth. 

Just fishin' to see if any one else out there is having issues with the lead cupel disposal or if anyone is trying the bismuth route?


----------



## samuel-a (Apr 10, 2010)

one can throw them used cupels to the e-scrap pile... it contains lead anyways....


----------



## Oz (Apr 10, 2010)

I wonder if the used cupels would be considered a high enough grade of lead ore for a smelter to be interested in.


----------



## 4metals (Apr 10, 2010)

Used cupels run 30 to 50% lead by weight, never have been able to locate a lead recycler to just take them. If you need documentation that they were disposed of safely, then a manifest is involved, then the cost starts going up fast.


----------



## Anonymous (Apr 28, 2010)

I looked into the idea around 97-98. Basically to reduce the amount of hazmat the laboratory was generating. I remember doing a lot of testing; but I never felt comfortable with the numbers when doing side by side comparisons. The assayers did not seems to notice any problems to speak of. 

I have had more statistic classes now and could tell if there was a difference in the Lead/Bismuth vs sampling/splitting bias. At the time, there was enough variability that I was not comfortable to make the switch.

I do not have the facilities to do these experiment; however, I would be willing to guide you in setting up standards, experiment, and statistical analysis if you are interested.


----------



## 4metals (Apr 28, 2010)

Thanks for the offer but it's not my issue. Because of its cost, Bismuth for cupellation is 3 times as costly to do an assay. For 2 cups bismuth costs $2.60 and lead $.88 so a busy shop is only about to change when they have to. 

I did some work for a refiner in the midwest, running 200 plus assays a week, to work out the kinks between using lead cups and bismuth cups. He's ready to make the switch but at a difference is basic supplies of $350 a week he's waiting for the industry to make the shift. 

I'm just looking to see if anybody is considering the change, or even doing the testing just in case.


----------



## NobleMetalsRecovery (May 25, 2010)

A few years ago I spoke with a person, (don't remember who) that told me that they were using bismuth for assays instead of lead. The main thing they pointed out was the need to use a magnesia cupel in place of a bone ash cupel. Every since then I have been using magnesia cupels. Not for assaying, but as melting dishes.


----------



## Lou (May 25, 2010)

They work great as melting dishes for practically any metal!


----------



## lazersteve (May 25, 2010)

I sell these on my website, but the ones I sell are only able to hold about 1 ounce of gold.

They are very durable though. Before I started doing larger batches of metals I used them exclusively for melting.

Steve


----------



## goldsilverpro (May 28, 2010)

4metals said:


> I was wondering if anyone has substituted bismuth for lead in their assaying procedures? I had done fire assays, in side by side comparisons, in the late '90's when the concerns about lead pollution were getting more attention in the press and with the EPA and found it to be an effective substitute but its cost made it prohibitive.
> 
> Well the EPA is back and asking questions as to the disposal of used cupels from fire assaying so I sense there may be a renewed interest in the future. It's a shame to say but most assayers simply toss their used cupels in the trash and that behavior may soon be stopped. The only way to avoid the manifested collection of the cupels as a hazardous waste is to cupel with bismuth.
> 
> Just fishin' to see if any one else out there is having issues with the lead cupel disposal or if anyone is trying the bismuth route?



I did find a patent on using bismuth for assays.

http://www.google.com/patents?id=JBQkAAAAEBAJ&printsec=abstract&zoom=4&source=gbs_overview_r&cad=0#v=onepage&q&f=false


----------



## goldsilverpro (Jan 18, 2011)

4metals,

I thinking about switching to bismuth. Legend-Reno wants $1000/55 pounds and that's about 5 times litharge. I'll mainly be using it for production and research, so I'll only be running about 4/day. Any major differences or problems? Same flux mixtures? Same techniques? I'll be using magnesia cupels. They also sell bismuth cups, which I assume replaces the lead foil. Does bismuth require an exhaust? How are PGMs affected?

Chris


----------



## qst42know (Jan 19, 2011)

The patent you found has the special flux ratios on page 2.


----------



## goldsilverpro (Jan 19, 2011)

qst42know said:


> The patent you found has the special flux ratios on page 2.



That flux formula didn't seem that special to me.


----------



## Westerngs (Dec 10, 2011)

I remember that Asarco in East Helena Montana did a lot of research work on switching to bismuth. I think they published a paper on this.

I do know that lead bearing cupels need to be disposed of as hazardous waste. I am currently paying about $600 per 55 gallon drum for disposal.

4Metals, give me some more information on what kind of questions EPA is asking. If they are getting more strict on lead usage, emissions and waste disposal I will need to know as I generate about 2 drums of waste cupels a year.

Thanks,


----------



## 4metals (Dec 10, 2011)

Used cupels fail TCLP for lead and thus must be manifested. $600 a drum seems reasonable as the full drums are in excess of 600 pounds and $1 a pound isn't a bad trade-off as compared to the cost of switching to bismuth assaying. 

Who are you using for the removal?


----------



## Westerngs (Dec 10, 2011)

I use a local company. They then haul the waste to a hazardous waste landfill in Nevada. I am in the western part of the country.

I will send you the name of the landfill on Monday or so.

If you are in the East, your shipping costs to Nevada will be expensive, you might try to find a hazardous waste landfill closer to you. I do know a cupel generator in the northeast, I will ask them for their disposal method and costs.


----------



## Westerngs (Dec 12, 2011)

My friend in New York state uses Veolia Environmental Services and the cupels are processed through the West Carrollton Ohio facility. The cost is $195.00 per drum.


----------



## duncan (Jun 8, 2012)

The bismuth assay has been looked into for years. Most production Assay labs don't use it because of cost.

One of the guys in our lab wants to try and sell used cupels to be ground up and mixed with concrete for radioactive shielding. I thought that was a pretty good idea.


----------



## Eu_citzen (Apr 5, 2017)

Bringing back a ancient thread in the hopes of some new insight into the matter.

Has anyone done some testing in regards to using bismuthoxide for assaying?

Otherwise...
Once I get my furnace up and running again, I'll try and run some side-by-side comparisons.


----------



## 4metals (Apr 6, 2017)

I haven't run any more samples with bismuth since I first did the evaluations in the '90's. The cost is a big factor and no one in a declining (USA) refining market is looking to spend any more money than they have to. 

It would be a good change for the assay industry but it needs to be driven by environmental regulations, in the US the majority of the refiners tend not to be the type to spend the substantial extra dollars just to be green. They would not be classified as "tree huggers!"


----------



## Eu_citzen (Apr 6, 2017)

4metals said:


> I haven't run any more samples with bismuth since I first did the evaluations in the '90's. The cost is a big factor and no one in a declining (USA) refining market is looking to spend any more money than they have to.
> 
> It would be a good change for the assay industry but it needs to be driven by environmental regulations, in the US the majority of the refiners tend not to be the type to spend the substantial extra dollars just to be green. They would not be classified as "tree huggers!"



I hear ya. I got myself approx 1 Kg of bismuth from a fireworks shop, to try out.

My assaying is done for my own prospecting needs only, not much refining going on here. 
Well, not yet anyway.

Pricing is second concern to health & disposal issues with lead, I won't be doing a whole lot of assaying.
So it makes a attractive alternative for me.

What were your findings in the 90's, if you remember? Any interesting observations?

Some preliminary testing I did (before the furnace broke!) indicated that it seems beneficial to add a bit extra bicarbonate as to improve results on assays containing silver. Otherwise I'd tend to get somewhat low results on that using bismuth.

Well, it'll be a week or two before the furnace is ready for action, so I'm reading all I can get my hands on.


----------



## 4metals (Apr 6, 2017)

The only thing I had issues with was replacing litharge with the bismuth oxide for sweeps assays when there was a high concentration of chromium in the sample. Back then I assayed a lot of jewelers sweeps and green rouge had high chromium. It was difficult to assay with a litharge flux and even more difficult with a bismuth oxide flux. 

Checking old notebooks, my comment was if green (that's chromium) and an unacceptable spread between cups results with a green rouge specialty (litharge) flux, forget bismuth oxide, unacceptably low results.


----------



## Eu_citzen (Apr 6, 2017)

4metals, Thanks! Curiously, chrome oxide is very rarely used for polishing jewelery these days, in Sweden.
I see more iron oxide based polishing compounds.


----------



## 4metals (Apr 6, 2017)

True but I'll wager money I'm a lot older than you! Green rouge was very popular in the '80's and '90's. Today not as popular. I believe it is used to polish Platinum though.


----------



## Eu_citzen (Apr 7, 2017)

:lol: 4metals, Chances are you're right about that.


----------



## goldrun (Jun 10, 2017)

Does bismuth require an exhaust? Is it imperative to use magnesium cupels?


----------



## 4metals (Jun 12, 2017)

I wouldn't do any cupellation without exhaust!


----------



## goldrun (Jun 13, 2017)

goldrun said:


> Does bismuth require an exhaust?


Sorry for this one  Even bismuth is less toxic than lead it is necessary to have axhaust :!: What about magnesia cupel? Someone :?:


----------



## 4metals (Jun 13, 2017)

Sorry all of my first hand experience with bismuth cupellation was with bone ash cupels


----------



## Eu_citzen (Jun 18, 2017)

What ever you do, don't use pure cement cupels. (in case someone still makes cupels)
A 50/50 mixture of bone ash and cement gave good results, however. Bone ash cupels also worked.

Haven't tried magnesia cupels, don't have any at hand.

ALWAYS have an exhaust.


----------



## Yggdrasil (Apr 18, 2022)

I am aware that this thread is old but since my question is on topic I hope its ok.
We have tried to cupel with Bismuth, but it failed. 
The button had slags and was very brittle. It also had prills around it.
I was not there so I'm just relaying the information. 
Are there some things not to do with Bismuth in stead of lead?
He was out of lead, but had Bismuth and gave it a try, it's for internal use no need for high precision.
Regard Per-Ove


----------

