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View Full Version : What kind of Crucible for the Lead-Ore-Borax part of a Fire Assay ?



gunDriller
4th October 2011, 02:42 PM
http://www.mine-engineer.com/mining/assay2.htm

reference to Fire Assay process for testing for presence of gold in ore samples; will reply to my first post to add pictures etc.

gunDriller
4th October 2011, 03:06 PM
http://media1.riogrande.com/Products/Images/Large/704155.jpg

I have one of these crucibles and a kiln that goes up to 2000 F. The graphite crucible in the picture is about 3 inches diameter and about 5 inches high, weighs about 5 pounds.


That web page describes the fire assay process as a 2 step procedure.

As I understand it - first you mix the ground up ore sample with powdered lead and borax.

It doesn't tell me the amounts so I am going to go with about 2 ounces (by volume) or ore, 2 ounces of lead, and 1 ounce of borax. I'll put it in the crucible, heat it up to 2000 F, and let it cool off.

It makes it sound like the kiln should be pre-heated.

I'm wondering if the kiln is not pre-heated, if the molten lead just oozes to the bottom of the crucible, without getting a chance to mix with any gold in the ore sample.

But my kiln is not the greatest, it's not so easy to pre-heat to 2000 F and then open the door and insert the loaded crucible.

Will it still work if you don't pre-heat the kiln ?


When it cools, according to the process description at the link, you end up with a 'thing' with lead at the bottom, and some kind of slag on top. If all has gone well, whatever gold was in the ore sample has ended up in the lead 'button'.


Part 3 of the process - you take the lead and put it in a ceramic crucible called a "cupel." In my case I got some #5 bone ash cupel's from these guys -
http://www.minerox.com/

The lead soaks into the cupel, and if there was any gold in the lead, it is left in the bottom of the cupel as a tiny bead.


Part 2 -
I have a hunch that I'm using far more lead than my #5 cupels can absorb, so I was going to re-melt the lead after Part 1, and then pour it on a smooth ceramic-ish surface (e.g. concrete floor). then cut the resulting lead sheet up into small pieces & weigh them, and divvy them out to the cupels. Then when I do the part 3, I might have 6 cupels each with 10 grams of lead.


DANG I sure would like to open that kiln door after part 2 and find a tiny bead of gold in the middle of the cupel ! ;)


Beefsteak, Crazy Chicken, whoever has done the fire assay process, and every body else, I welcome your feedback.

Am I on the right track ?

Are my proportions of lead/ore sample/ borax OK ?


All I have is the graphite crucible, so I was going to use that for Part 1 and Part 2, unless it gets messed up by Part 1. They're only about $30 from Rio Grande -
http://www.riogrande.com/Product/Salamander-Clay-Graphite-No-2-Crucible-55-lbs/704155?pos=8

A picture of the #5 bone ash cupel - they're only about 1" high and 1" wide -
http://minerox.com/images/products/M%208952full.jpg

Quixote2
4th October 2011, 04:56 PM
make your own with bone ash and cement plus water

http://www.google.com/#sclient=psy-ab&hl=en&source=hp&q=fire%20assay%20procedure&pbx=1&oq=fire%20assa&aq=2&aqi=g1g-s1g2&aql=&gs_sm=sc&gs_upl=5780l7786l1l11759l7l7l0l0l0l0l363l1671l0.2. 4.1l7l0&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=8bdce738706c865e&biw=1133&bih=1023&pf=p&pdl=300

http://www.google.com/#hl=en&cp=20&gs_id=5s&xhr=t&q=clay+cupel+crucible+fire+assay&pf=p&sclient=psy-ab&source=hp&pbx=1&oq=clay+cupel+crucible+fire+assay&aq=f&aqi=&aql=&gs_sm=&gs_upl=&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=8bdce738706c865e&biw=1133&bih=1023

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=9827

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=5650&hilit=portland+cement

http://nevada-outback-gems.com/Prospecting_Basics/Basic_fire_assay.htm

http://www.prospectorsparadise.com/html/assaying.html

Quixote2
4th October 2011, 04:56 PM
make your own with bone ash and cement plus water

http://www.google.com/#sclient=psy-ab&hl=en&source=hp&q=fire%20assay%20procedure&pbx=1&oq=fire%20assa&aq=2&aqi=g1g-s1g2&aql=&gs_sm=sc&gs_upl=5780l7786l1l11759l7l7l0l0l0l0l363l1671l0.2. 4.1l7l0&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=8bdce738706c865e&biw=1133&bih=1023&pf=p&pdl=300

http://www.google.com/#hl=en&cp=20&gs_id=5s&xhr=t&q=clay+cupel+crucible+fire+assay&pf=p&sclient=psy-ab&source=hp&pbx=1&oq=clay+cupel+crucible+fire+assay&aq=f&aqi=&aql=&gs_sm=&gs_upl=&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=8bdce738706c865e&biw=1133&bih=1023

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=9827

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=5650&hilit=portland+cement

http://nevada-outback-gems.com/Prospecting_Basics/Basic_fire_assay.htm

http://www.prospectorsparadise.com/html/assaying.html

http://www.tomslibrary.net/p_wk_fR1.htm

http://www.tomslibrary.net/Link_Wf.htm

gunDriller
4th October 2011, 05:48 PM
make your own with bone ash and cement plus water

THANKS !

to make bone ash - can i just take some bone meal (like they sell at garden supply stores) and heat it up in the fireplace to about 1500 F for an hour ?


in the write up at

http://www.mine-engineer.com/mining/assay2.htm

it sounds like this assay technique 'gets' / extracts most of the gold, enough to make it useful as an analytical tool.


so - why not use it as a production process ?

you would end up with a batch of lead-filled used cupels, but i'm pretty sure that the lead can be extracted from the used cupels using a centrifuge or something.


my kiln heated up remarkably fast, got to 1500 F in a half hour, usually it takes longer.

http://oi52.tinypic.com/14lokk1.jpg

ore, lead powder, borax.

the upside down cup is the crucible. it is looking very used.

the little cup is the cupel.


may your cupel runneth over ;)

Quixote2
4th October 2011, 06:34 PM
Just buy the bone ash at a local craft/pottery supply store, about $2 a pound.

http://www.axner.com/bone-ash-di-calcium-phosphate.aspx

http://www.google.com/#hl=en&cp=12&gs_id=1d&xhr=t&q=bone+ash+production&pf=p&sclient=psy-ab&source=hp&pbx=1&oq=bone+ash+pro&aq=0v&aqi=g-v3&aql=&gs_sm=&gs_upl=&bav=on.2,or.r_gc.r_pw.,cf.osb&fp=8bdce738706c865e&biw=1133&bih=1023

You cannot keep using the bone ash cruicble. The lead metal is oxidized to lead oxide and absorbed into the bone crucible pores. The crucibles are sized to absorb only so much material. After use you cannot reclaim the lead from the lead oxide by melting. Throw away the used bone ash crucibles. (Do not tell the EPA that you are pitching them in the muncipal dump.)

gunDriller
6th October 2011, 07:44 AM
Well, I managed to get my lead out of the crucible.

And then I poured it onto a steel sheet to make a crude lead sheet.

Then I took some pieces of that and put it in the cupel.

And it got a Spongey Orangey Crust - I'm thinking that's Lead Oxide. From doing a web search, I'd say that is almost definitely lead oxide.

The lead didn't soak into the cupel, as it was supposed to.

Back to the instructions - "So, the cupel's with the lead buttons are again placed in a Assay or Cupellation furnace, heated to about 2,000 deg F and the lead is absorbed into the cupel, leaving only a tiny gold bead. The cupels are removed from the furnace, allowed to cool and the gold bead is weighed."

I will try it again. I don't think I got it up to 2000 F.

Pics -

http://oi55.tinypic.com/5x0s3b.jpg

Crucible + Lead + Slag.


http://oi55.tinypic.com/2z556s9.jpg

Lead


http://oi55.tinypic.com/25zm9fo.jpg

Lead Oxide on Rim of Cupel.

E. Haney
6th October 2011, 08:32 AM
The short answer is no, that won't work.

It appears you have a measuring cup of metallic lead, you need to use lead oxide (PbO).
Mixing ore with metallic lead and borax will result in the lead melting (at approx. 622F) and sinking to the bottom of the crucible, as the heat is increased (Yes, you should start with the furnace cold or fairly warm, but not at fusion temperatures and gradually raise the temperature) at about 1000F the borax will begin to melt (the use of 20 Mule Team or any hydrated borax is discouraged, as it heats the water boils off and the borax 'grows' and can overflow the crucible taking ore and flux components with it) and begin to form compounds with the bases of the ore. But the 'collector', the lead, is now sitting at the bottom of the crucible where it is of little use.
The use of lead oxide (a powder) thoroughly mixed with the powdered ore and powdered flux components forms an intimate mix where as the lead oxide reduces beginning at approx. 950F, the resultant microscopic beads of molten lead alloy with the Ag and Au contained in the ore/flux mix, the base metals oxides for the most part dissolve into the flux as the temperature of the furnace is increased the flux becomes more fluid and the heavy lead alloy drops to the bottom and collects as a button.
A simple flux/ore charge:
1 part by weight Ore
1 " " " Sodium Carbonate (washing soda [baking soda {1.6 parts} can be substituted, but like 20 MT borax is hydrated and contains CO2, so it will 'grow' as well and release carbon dioxide gas])
1/2 part by weight Borax
2 1/2 parts lead oxide (PbO)
1/2 part flour (ordinary baking flour)
this is thoroughly mixed until it is homogeneous, added to the crucible, heated with increasing temps to fuse (dull red) when it is no longer bubbling, heated to fluidize at a bright yellow heat.
Allowed to settle, then removed from the furnace and poured into a cone mold.

As BeefSteak pointed out this is a procedure that is done outdoors or with a ventilated furnace due to lead vapor.

As far as you being able to do a cupellation, I doubt you can do it unless your furnace is a front door vertical opening model.

Your best bet for crucibles are clay smelting crucibles, cheap, disposable, non-reactive, the carbon in your graphite crucible will react with any oxides in the ore, a good thing for the fusion, but it eats the crucible thinning it, a bad thing if it breaks while removing it from the furnace or pouring.

E. Haney
6th October 2011, 08:44 AM
Is that a #5 cupel?
How much lead did you load? A #5 absorbs 16.6g Pb.

From your photo, you are clearly too cold, the lead oxide needs to melt and absorb into the cupel, some has as you can see a yellow staining.
What you have is known as a frozen assay, they cannot be recovered.

I guess I should ask what your intentions are.
Are you attempting to extract values from ore in this manner? If so, it's not really the way to go, and will be quite expensive and time consuming.
If you are just experimenting, more power to you, be careful, read, try things, but realize you will lose some gold and silver, it's inevitable.
If you are trying to do accurate assays, I hate to say it, but accuracy in fire assays is not a 'home-made' venture, can it be done? Yes. But the proper equipment is required.

gunDriller
6th October 2011, 05:46 PM
Is that a #5 cupel?
How much lead did you load? A #5 absorbs 16.6g Pb.

From your photo, you are clearly too cold, the lead oxide needs to melt and absorb into the cupel, some has as you can see a yellow staining.
What you have is known as a frozen assay, they cannot be recovered.

I guess I should ask what your intentions are.
Are you attempting to extract values from ore in this manner? If so, it's not really the way to go, and will be quite expensive and time consuming.

Yes, it is a #5 Cupel. The store guy told me it would absorb its own weight in lead; it weighs about 33 grams. maybe if i had a perfect lead sphere 33 grams would fit in the shallow cup on the cupel.

15 grams makes much more sense.

i think it was when i was talking to a few metal detector guys, one of them told me about fire assays.

as a way to see if there is gold in a particular ore sample. then i did a web search and realized i had most of the tools.

from the mine-engineer.com/mining/assay2.htm
write-up, they make it sound like a production-ready technique (if you have the right tools).

the most sensitive scale i have is a Salter Brecknell PB-500, which goes down to .1 gram. if i found .1 gram of gold in a 15 gram lead sample, well that's a lot of ounces per ton, i sure don't expect to find that.

for starters, i need a more accurate scale.

i measured the lead before & after the assay. 115 grams before, 96 grams after. it didn't spill but my guess is, some of those fumes infused lead into the fire-bricks in the furnace, or maybe went into the orange glass on top of the metallic lead in the bottom of the graphite crucible.


mainly, yes, i am doing it to learn.



If you are just experimenting, more power to you, be careful, read, try things, but realize you will lose some gold and silver, it's inevitable.
If you are trying to do accurate assays, I hate to say it, but accuracy in fire assays is not a 'home-made' venture, can it be done? Yes. But the proper equipment is required.

THANKS MUCHO everybody - Beefsteak, E. Haney, & Quixote ! ;)

i just started 2 more with about 14 grams in each one.


on the safety issue - obviously something that is easy to overlook in the enthusiasm/ gold fever of the moment.

for most of the work around the kiln, which is in the garage, i held my breath while i was in the garage.

i would work for a minute or 2, then go outside and get a breath, etc. i made a mistake and i left the hot crucible near the plastic meter on the oven, i didn't want to breathe that smell anyway.


work mode #2 - i was using a propane-oxygen torch to try & get the lead to "ball up" so it would fit in the cupel better. i also held my breath for that. at one point i put the lit torch down, while i stepped away to get a breath. and it burned the concrete step and sent a little chunk of it flying. so i know i held my breath for that part.


at the same time, i am building a fume hood workbench in the garage. about half an hour after i turned off the kiln, i went back in the garage and worked on that for about a half hour. now i wonder if i might have gotten any lead fumes then.

it makes me think about water - it doesn't boil till 212 F, but obviously air can contain water at lower temperatures.

i did see lead vapor rising off the lead in the crucible when i re-melted it and took it out of the kiln, hot, and poured it on the steel sheet. referring to the 96 grams of lead that was in the crucible beneath the orange glassy stuff.

i wonder what happens to that lead vapor. does it fall back to the ground (the garage floor in this case) because lead is heavy ?

gunDriller
7th October 2011, 07:06 AM
http://oi52.tinypic.com/264kiys.jpg

a tiny bead of metal in the middle of the bupel. crappy pic taken with a flashlight or flash, i forget. it's about 6 AM, no daylight available.

the set-up for this go-round -

http://oi56.tinypic.com/241a6wi.jpg

2 cupels loaded with lead from ore-borax process, and the "frozen assay". the frozen assay was on the floor next to the kiln & i accidentally kicked it over. there was a small bead of lead about the size of a piece of corn or hominy, and the cupel was about halfway stained. thought i would just give it a try.

i turned the kiln off last night. this morning the 2 freshly loaded cupels had a little bit of crust on them. the re-tried frozen assay just had this tiny little bead, as shown in the top photograph.

no disrespect to E. Haney - i believe you that a good working procedure is to abandon a frozen assay.

later this morning, i will take it to a local coin dealer for a nitric acid test.

it's so small i can't tell what color it is, besides shiney and lighter colored than lead.

E. Haney
7th October 2011, 08:05 AM
Yes, it is a #5 Cupel. The store guy told me it would absorb its own weight in lead; it weighs about 33 grams. maybe if i had a perfect lead sphere 33 grams would fit in the shallow cup on the cupel.

15 grams makes much more sense.

The rule is a cupel will absorb 3/4ths it's weight in PbO (lead oxide), but this should be reduced slightly when figuring lead absorption due to the lead oxide weighing 7.1679% more than metallic lead.


i think it was when i was talking to a few metal detector guys, one of them told me about fire assays.

as a way to see if there is gold in a particular ore sample. then i did a web search and realized i had most of the tools.
It is the standard and most accurate way, in-spite of what others may believe, but it requires careful measures, accurate techniques, and attention to detail. Don't become discouraged, we learn by doing, experiment, have fun, but more than anything be careful, lead fume will sicken you, if not kill you, it is insidious, lead collects in bone and tissue, you may not feel bad now, but with repeated exposures you can become very ill.
Molten metal and slags burn instantly, a small drop on the top of even a leather shoe or boot will burn through and sizzle into your flesh.
Slags are essentially glass, large pieces should be discarded in a study container, because they are contaminated glass, as it cools internal stresses are induced, a large piece can shatter spontaneously.
Always heat a new crucible slowly, preferable empty to a red heat before using it, new or hardly used crucibles contain moisture, if placed in a hot furnace they can explode from the steam generated.




the most sensitive scale i have is a Salter Brecknell PB-500, which goes down to .1 gram. if i found .1 gram of gold in a 15 gram lead sample, well that's a lot of ounces per ton, i sure don't expect to find that.

for starters, i need a more accurate scale.
Yes, I'd say so. A tenth of a gram is not of much use for assay weights.


it didn't spill but my guess is, some of those fumes infused lead into the fire-bricks in the furnace, or maybe went into the orange glass on top of the metallic lead in the bottom of the graphite crucible.
Some lead does go off as fume (approx. 2% at proper cupellation temperatures) and some of this will be absorbed by the furnace lining, unfortunately this will now fume off every time the furnace is heated even if it's not being used for fusions and cupellations. I hate to say it, but it is a toxic nightmare, which is why ventilation is important.




at one point i put the lit torch down, while i stepped away to get a breath. and it burned the concrete step and sent a little chunk of it flying. so i know i held my breath for that part.

This illustrates the point of slowly heating your new or not used in a while crucibles, the flame boiled the water in the concrete and blew the chunk out, the same can happen to a crucible.



at the same time, i am building a fume hood workbench in the garage. about half an hour after i turned off the kiln, i went back in the garage and worked on that for about a half hour. now i wonder if i might have gotten any lead fumes then.

it makes me think about water - it doesn't boil till 212 F, but obviously air can contain water at lower temperatures.

i did see lead vapor rising off the lead in the crucible when i re-melted it and took it out of the kiln, hot, and poured it on the steel sheet. referring to the 96 grams of lead that was in the crucible beneath the orange glassy stuff.

i wonder what happens to that lead vapor. does it fall back to the ground (the garage floor in this case) because lead is heavy ?
A fume hood with a good draft (suction) is this most important thing you'll do.
As for the fumes, they will condense and drop out of the air, unfortunately all over everything in the garage, including the floor and surfaces, while I have no idea about your home life, if you have children and/or pets this is a no entry zone even when you are not working, also you need to remember anything you touch you are transferring lead to yourself, your shoes, your clothes, your hands, thorough washing is important before eating, drinking or smoking. Again, you or a loved one may not develop symptoms for a long time after many small exposures.

One final thought, if in time you get to the point where, and I'm sure with patience and practice you will, you get nice buttons from your cupellations, refrain from jumping too high, they contain the gold and the silver from the ore, not just the gold, so they are going to look a lot more valuable than they are.

E. Haney
7th October 2011, 08:32 AM
You are doing much better.
The tiny size is in my opinion because of the use of metallic lead as opposed to litharge (lead oxide) as i had said the metallic lead just melts and sits on the bottom of the crucible. But all-in-all a nice job.

You should be heating your empty cupels to bright red before adding the lead (Yes, I know, not an easy task, but it is the correct way). Heat the cupels, add the lead, close the door (to retain and quickly heat the charge) crack the door a bit (yes, I understand the heat will escape, but you need to admit some air [oxygen] to oxidize the lead in to PbO, this is what the cupel absorbs) with a closed door, once the oxygen is utilized effectively stops the cupellation.


no disrespect to E. Haney - i believe you that a good working procedure is to abandon a frozen assay.
No disrespect was detected, I may have misspoken, I meant for an accurate assay, you will have substantial gold and silver loss when reprocessing a frozen assay.
As far as for experimentation and learning, as long as you can accept losses, do what you please, well except carelessness, that can be painful and deadly.

E. Haney
7th October 2011, 08:53 AM
A few other things:
It's a good idea to lay down a layer of bone ash or magnesia bedding on your furnace floor, spills and overflows happen and are a pain to clean up, the bedding, after a spill can be scraped out quite easily, also some fluxes will eat the firebrick lining, relining your furnace isn't nearly as cheap as a layer of bone ash. I see you are using pliths, very nice.

Pre-mixed fluxes are available from on-line prospecting sites, or of course if you live near 'gold country' in brick and mortar detectoring/prospecting/mining shops. These will improve your yields. Though if, I should say when, you go this route, get a respirator, the last thing you'll want to do is inhale these dusts.

Also, though they aren't cheap, lead detecting swabs are available to test surfaces and your skin for residual lead contamination.

gunDriller
7th October 2011, 01:12 PM
A few other things:
It's a good idea to lay down a layer of bone ash or magnesia bedding on your furnace floor, spills and overflows happen and are a pain to clean up, the bedding, after a spill can be scraped out quite easily, also some fluxes will eat the firebrick lining, relining your furnace isn't nearly as cheap as a layer of bone ash. I see you are using pliths, very nice.

Pre-mixed fluxes are available from on-line prospecting sites, or of course if you live near 'gold country' in brick and mortar detectoring/prospecting/mining shops. These will improve your yields. Though if, I should say when, you go this route, get a respirator, the last thing you'll want to do is inhale these dusts.

Also, though they aren't cheap, lead detecting swabs are available to test surfaces and your skin for residual lead contamination.

now if i could just find a cheap source of powdered lead !

i made the lead powder using a large file and a kilogram ingot of lead. and about 2 hours of elbow grease.

Sigma-Adlrich has powdered lead, but it's expensive.


i got back from the coin shop & the nitric acid test.

he put the metal sphere DUT (device under test, electronics industry terminology) onto a piece of slate that they use for other assaying purposes. then he put a few drops of nitric acid on top of it.

i stood back and held my breath, but he acted like it was no big deal.

the teeny sphere did not dissolve. it bubbled for about 30 seconds, and it turned black, but it did not appear to dissolve. it's not spongey, though it must have lost some mass when it was bubbling.


i thought most metals would dissolve in nitric acid.

http://www.finishing.com/509/33.shtml

http://www.ishor.com/RefineAgInstruct.php

2 links that come up when you do a web search for 'silver dissove nitric acid'


what do you think is in the sphere ?

what other metals would not dissolve in nitric ?

"Nitric acid reacts with most metals. This characteristic has made it a common agent to be used in acid tests. Some precious metals, such as pure gold do not react with nitric acid, though pure gold does react with aqua regia, a mixture of concentrated nitric acid and hydrochloric acid. However, some less noble metals (Ag, Cu, ...) present in some gold alloys relatively poor in gold such as colored gold can be easily oxidized and dissolved by nitric acid, leading to colour changes of the gold-alloy surface. Nitric acid is used as a cheap means in jewelry shops to quickly spot low-gold alloys (< 14 carats) and to rapidly assess the gold purity."

http://en.wikipedia.org/wiki/Nitric_acid


what is described in Wikipedia as a low-gold alloy, that sounds like what i saw.

however, i'm not sure if the nitric acid test is conclusive.

color-wise, it is black or very dark gray.

gunDriller
8th October 2011, 07:46 AM
Gunny,

Locating cheap litharge is tantamount to De Leon's fountain of youth GPS coordinates.
Good luck with that one.

Nitric reaction which creates black or very dark grey coloration in response to being applied to your solid remainder from your cupellation attempt is nothing more than a definitive indicator of the presence of base metals in your ball. Testing is a micron depth test, nothing more.

Nitric will not entirely dissolve the base metals present unless there is greater than 25% of base metals in your ball if it is truly alloyed with a noble metal, such as gold.

Nitric will dissolve Palladium, and leaves a yellow coloration on a Q-tip, for example.
Nitric will NOT dissolve Platinum, nor does it turn platinum black.

You are now in the world of ratios determining what you are going to experiment doing next. In your 100% unknown solid, if base metals are comprise LESS THAN 25% of the whole, the ball will remain intact and no appreciable dissolution will occur. It can't. It's a physics thing...

You've successfully tested that undissolved bead. What experimental procedure are you going to perform next?


beefsteak

are you saying that the teeny test sphere is
A/ definitely part base metals
B/ may or may not contain gold
B/ may or may not contain silver

i don't know what to do, except to go work on other stuff (planting trees etc.)

i wonder if the sphere actually contains impurities from the lead brick i filed down, not from the ore sample.

it makes me wonder if i should flatten the test sphere into a thin sheet before doing the nitric, so it can penetrate better.

i also think of the stannous chloride test.

gunDriller
8th October 2011, 12:35 PM
Gunny,

A/ Yes B/ Yes C/Yes.

PS...the coin shop owner who was willing to test with nitric and not hold his breath, for example, has a different opinion of the value of his lungs than I do. Most assuredly this is the case if he has been doing this same action repeatedly over decades. Breathing any amount of nitrous oxide is unacceptable in my circles, let alone repeatedly.

beefsteak


Thanks ! I think it might take me 6 months to fully understand.

I read the Google-search and some of the links.

I couldn't take a picture of the bead for the exact reason you mentioned. it's in the baggy with the orange crud & the cupel, I was talking to the guy at the coin shop, i lost track of it but i know it's in there.

It sounds like flattening it is a good next step.


i have been web-searching for "what metals don't dissolve in nitric acid".

so i guess the question is, besides gold, what metals don't dissolve in nitric acid ?

sorry if you already answered that, my vision isn't great and it is hard for me to absorb information visually.


anyway i found it, i used a flat needlenose and a bigger wrench to flatten it, 'it' being the black metal bead.

i guess i'm going to have to go back and buy something at the coin shop. bummer ;)

i offered to pay money for the assay task and the guy refused it. so it's sort of basically them doing me a favor. if i go back, i would feel wierd using their assay assistance without doing something that benefits them. i don't want them to start groaning when i walk in the shop, "the guy who asks 8 million questions."

i also offered him half of my box of nitrile gloves - this time and last time he was elaborating on the effect of nitric on his skin. he has lost lots of the feeling and his fingers look a little like he held them against a grinder or belt sander.

a very interesting first hand look at the effects of prolonged nitric use.

this isn't the guy who runs the coin shop, he's a friend and employee of the owner. why they don't take basic steps health-wise, i don't know except to say, i notice in some cultures, dangers that you can't see, people don't worry about.

he said they stopped buying sterling silver, perhaps to spare his skin. it sounded like his skin used to be in worse shape.


as far as a lead assay technique in general, so far i've gotten a lot of knowledge for a minimum emittance of lead. i like the technique of using lead, except for the toxicity of the lead.

i would think people have tried doing this basic procedure using other metals. it would be handy if you could do it using aluminum and a cupel that absorbs aluminum.

my guess is when i follow some of those links that will become more clear.

gunDriller
9th October 2011, 04:02 PM
Gunny,

additional notes for your encouragement. Since you've experienced a modicum of success in your learning curve while using metallic lead as opposed to PbO, here are 3 suggestions for you.

1) Since litharge isn't cheap....
Since whittling lead ingots is laborious...
there is a 3rd alternative: plumbers lead. Found at any hardware store. Looks like shredded up steel wool, but it's lead instead.

2) It is best practice to NEVER get cupellation temps above 1850F !!! NEVER!
Best maintain 1800F when performing cupellation.

3) Nitric can be purchased by ordinary folk like yourself, in small quantities, and yes shipped directly to you by legit sources. STAY UNDER THE HAZMAT quantities when inquiring about purchasing from a supplier. Those hazmat restrictions kick in above a certain fluid ounce threshold. Yes, you'll be buying more often, but so what? You're not going to bathe in the stuff.

beefsteak


one of the scrap metal places in town lets me cherry-pick lead out of their lead barrel and charges me 46 cents a pound.

that plumber's lead sounds helpful !


at this point the thermometer on my kiln is not functional. 3 hours seems to be good for 2000 F. i can back off on that + maybe get a better thermometer eventually.

gunDriller
10th October 2011, 07:06 AM
in order to shut the door on the kiln, i use a 1/2" woven rope tied around the outside. then cinch it up tight the way the door latch should be.

the kiln's about 20 years old. if i don't use a rope, it has a real hard time getting to the mid 1900's F to melt copper or gold.

so maybe i should put a new latch on.

E. Haney
10th October 2011, 08:08 AM
Nitric will not entirely dissolve the base metals present unless there is greater than 25% of base metals in your ball if it is truly alloyed with a noble metal, such as gold.


You are now in the world of ratios determining what you are going to experiment doing next. In your 100% unknown solid, if base metals are comprise LESS THAN 25% of the whole, the ball will remain intact and no appreciable dissolution will occur. It can't. It's a physics thing...
beefsteak

I'm sure in your haste to post you mistakenly inverted your ratios, but in case you didn't, you need to inquart to at least a gold/silver ratio of 25/75, though beads of low gold content need a ratio of a high as 1/20.

gunDriller
10th October 2011, 08:31 AM
question about the use of lead for a fire assay -

"The base metals, copper, lead, and zinc have been dissolved in the lead and absorbed by the cupel cup."

DANG ! that's convenient.

from
http://www.assaying.org/parting.htm

is it true ? does that mean my bead is silver and/or gold and/or PGM ?

does lead remove ferrous metals that sometimes occur with gold ?

from
http://www.prospectorsparadise.com/html/assaying.html
"In the trade they say, "if you can cupel it, you can sell it". Anything that remains after cupeling is precious metal."


i did test the lead ingot i used for the lead powder by putting a 14 gram chunk on the cupel. it soaked it all up. i wanted to make sure i wasn't getting metal from the lead source, thinking it was from the ore.

beefsteak
10th October 2011, 08:37 AM
Gunny,

I will not admit to "hasty error"...

Eustace's still functioning as a wannabe and incorrectly relayed what he THOUGHT I said. Then he compounded his error by not typing exactly what he was told to type in his reply from his ghostly (ghastly?) "Mr Q" and the truth got lost in the translation.

Beefsteak = real world of been there, done that, and most assuredly does not act as a mouthpiece or ghostwriter for someone else in an effort to draw attention. Attention for what: credibility as a newbie on a public forum? ? ?

Suggest you go back and re-read the proferred url from the 1871 text I posted above, thanks to Google's scanned references base, and let that be the final arbiter...that is if you need one.

----> http://books.google.com/books?id=lgFLAAAAYAAJ&pg=RA1-PA269&lpg=RA1-PA269&dq=parting+an+assay+bead&source=bl&ots=QbQFr93Gw2&sig=C16AtyK4iRg7r8b8HPcHYyOUuTQ&hl=en&ei=cWGQTp6-PMyJsALpzeS1AQ&sa=X&oi=book_result&ct=result&resnum=10&ved=0CFUQ6AEwCQ#v=onepage&q=parting%20an%20assay%20bead&f=false

I'm going to be the bigger man, gunny, and exit this thread of yours. Good luck with your experiments. What you need to know can be found in books and from real-life schooling, teachers, chemists. Just be careful of newbies on chatroom boards with hidden agendae. Look at how he messed up the inquartation discussion with his jealous--didn't tell you first--rant/response aimed at taking me down a peg or two.


beefsteak

E. Haney
10th October 2011, 08:41 AM
Suggestion: performing an inquartation is commonly done with silver. Then you have to get the silver back out and re-solidify. Most perform this silver recovery step by cementation, others drop it out as a curdish chloride and flux and fire it. Many prefer inquarting with Cu due to this much lower than silver cost per troy oz, and Cu's easy susceptibility to dissolution by HNO3.
That will release chlorine gas into his garage, you know, the same gas we used in war, to kill. Beefsteak, seriously, if a little knowledge is a dangerous thing, you should be licensed with the government.



Many prefer inquarting with Cu due to this much lower than silver cost per troy oz, and Cu's easy susceptibility to dissolution by HNO3.

Inquartation with copper while it does work is wasteful of nitric acid, it requires three times as much nitric to dissolve an equivalent amount of copper than silver.

E. Haney
10th October 2011, 09:23 AM
Suggest you go back and re-read the proferred url from the 1871 text I posted above, thanks to Google's scanned references base, and let that be the final arbiter...that is if you need one.


http://books.google.com/books?id=lgFLAAAAYAAJ&pg=RA1-PA269&img=1&zoom=3&hl=en&sig=ACfU3U1ybjASjFWp2934hZ73MUQJ8DiJGQ&ci=45%2C485%2C434%2C83&edge=0




I'm going to be the bigger man, gunny, and exit this thread of yours. Good luck with your experiments. What you need to know can be found in books and from real-life schooling, teachers, chemists. Just be careful of newbies on chatroom boards with hidden agendae. Look at how he messed up the inquartation discussion with his jealous--didn't tell you first--rant/response aimed at taking me down a peg or two.


That's really adult of you, running away because I pointed out you were/are in error.
If you suffer with dyslexia or perhaps need reading glasses please forgive me.
Otherwise, If you truly want to be a 'bigger' man, apologize.
I assure you, if you wish to make this a whip them out and measure contest, you will lose.

E. Haney
10th October 2011, 09:52 AM
question about the use of lead for a fire assay -

"The base metals, copper, lead, and zinc have been dissolved in the lead and absorbed by the cupel cup."

DANG ! that's convenient.

While a small amount may carry over to cupellation, the preponderance was removed in the slag from the fusion.



is it true ? does that mean my bead is silver and/or gold and/or PGM ?

does lead remove ferrous metals that sometimes occur with gold ?

.
Yes to the first, no to the second (that is the function of the flux)




"In the trade they say, "if you can cupel it, you can sell it". Anything that remains after cupeling is precious metal."


That is true, and in your case because you are not doing determinations (values per ton), your best scenario would be to save your beads, conglomerate them in one cupellation (they're small, why mess around parting these tiny things), and end up with a larger bead with is infinitely easier to work.

E. Haney
12th October 2011, 06:54 AM
Here's a few companies that sell supplies and chemicals.

http://www.anachemia.com/engnew/frame/product2.html (Chemicals, Fluxes, Assay supplies)

http://www.dfcceramics.com/ (Crucibles, Cupels, Furnaces, Bone ash, some chemicals and flux components [though large quantities])

http://www.minerox.com/ (Not much for your present interest, but none the less interesting)

http://www.actionmining.com/Catalog.PDF (A lot of goodies, including pre-mixed fluxes in small quantities)