# Assaying Karat GOLD 8K > 18K and FINE GOLD



## masarh (Dec 20, 2008)

i am writing this procedure as i was told but i need some explanation [if any]

ASSAYING KARAT GOLD
1.drill sample from bullion,
2.make three sub-sample of gold 0.25000 gramin in weight
3.add *0.32000*gram pure silver
4.foil in lead
5.put in cupell, and cupell in furnance at 960grade Celcius which forms a button contaning only Gold and Silver
6.roll the button to for a sheet,
6.boil with nitric acid in 32 baume 1 time for 20minutes
7.boil with nitric acid in 49 baume 2 times for 20minutes
8.wash with distilled water, and let dry
9.measure the left over of the gold and divide /primary sample
[for example leftover=0.15203 divide by 0.25000 =0.608‰

that means 608/1000 pureness


ASSAYING FINE GOLD
1.drill sample from bullion,
2.make three sub-sample of gold 0.25000 gramin in weight
3.add *0.45000*gram pure silver and *0.05000*gram Copper
4.foil in lead
5.put in cupell, and cupell in furnance at 960grade Celcius which forms a button contaning only Gold and Silver
6.roll the button to for a sheet,
6.boil with nitric acid in 32 baume 1 time for 20minutes
7.boil with nitric acid in 49 baume *3 times* for 20minutes
8.wash with distilled water, and let dry
9.measure the left over of the gold and divide /primary sample
[for example leftover=0.24239 divide by 0.25000 =0.96956‰

that means 969/1000 pureness

why is that i use for assay of karat gold 0.25gram Gold and 0.32gr silver 
while for FINE GOLD 0.25gram gold + 0.32 silver + 0.05 Copper


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## Noxx (Dec 20, 2008)

It will work. But I'm not sure about the accuracy though.

Why do you wrap your metals in lead foil ? Also, you should mention to use pure metals to inquart.


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## goldsilverpro (Dec 20, 2008)

The procedures given are excellent, although very exacting, fire assay procedures. They seem to follow the "Mint" method, which requires a lot of expensive equipment. For example, whoever wrote them had access to a 5 decimal place scale, which is quite expensive. A 4 decimal place scale should be adequate for decent routine results. Here are my comments of the various steps as to how I would do it, with lesser equipment. 

ASSAYING KARAT GOLD
1.drill sample from bullion,
Unless the bar was cooled immediately after pouring, there can be stratification and, therefore, differences in the compostition of the drillings. It is best, in my opinion, to sample in the well-stirred molten stage - stir with a carbon rod. This can be done by pin sampling (a small sealed glass tube containing a vacuum is quickly dipped into the molten metal - the tip of the glass melts and the gold is sucked into the tube - the glass is then broken away from the gold pin) or by ladling out a sample and pouring it into water (shotting).

2.make three sub-sample of gold 0.25000 gramin in weight
The more samples you run, the more samples you can average, and the better the final results. For routine work, 2 samples should be adequate. It is not necessary and is difficult to weigh exactly .2500 gram samples. Just weigh close to .25 grams and record the exact weight - for example, .2483 grams. Use this figure in the calculation in step 9.

3.add *0.32000*gram pure silver
In the "Mint" method, they use Platinum crucibles to part (dissolve) the silver from the gold. They also use a rolling mill (expensive) to roll out the Au/Ag bead into a long strip (step 6). They then shape the strip into a spiral. They only use a 2.2 to 1, silver to gold, ratio to prevent the gold from breaking up. Since I have no rolling mill, I flatten the bead with a clean hammer and anvil and end up with a thicker bead. Therefore, I use a higher silver ratio to insure that I dissolve all the silver. For a .25 gram sample, I use about .8 grams of silver - about 4 or 5 times more silver than gold. With this ratio, the gold will break up. You have to be very careful not to lose any of the gold specks.

4.foil in lead
Use about 10 grams of .005", silver-free, lead foil. Wrap the foil securely around the metals and form it into a package so it's about 1/2" square, or less.

5.put in cupell, and cupell in furnance at 960grade Celcius which forms a button contaning only Gold and Silver
Preheat the cupel at this temperature for about 20 minutes, or until it's a uniform color (no dark center), before adding the foil. A very slight amount of air is allowed to enter the furnace, in order to oxidize the lead. When all the lead and base metals are absorbed into the cupel, you are left with essentially a gold/silver alloy. Note: A full page could be written on the cupellation procedure.

6.roll the button to for a sheet,
Like I said, I flatten it with a hammer and anvil

6.boil with nitric acid in 32 baume 1 time for 20minutes
Starting with a weaker acid, the bead will break up less. I use #1 Coors porcelain crucibles on a hot plate. I usually use 7/1, distilled H2O/nitric, as a first acid. I use reagent grade nitric. Since my gold breaks up, I don't boil the acid. I heat it to near boiling until I see no more reaction. Carefully pour off the acid, without losing any black gold particles. This is easily done by swirling the crucible, to collect the gold into a pile, and then slowly pour out the acid down a glass rod.

7.boil with nitric acid in 49 baume 2 times for 20minutes
My second acid is 2 to 3, distilled water/nitric. Don't boil.

8.wash with distilled water, and let dry
I do 3, quite hot, water rinses. After decanting the final rinse, make sure all the gold is together, at the bottom edge of the crucible. Dry at very low heat on the hot plate. If it is too hot, it will spit gold out of the crucible. When *COMPLETELY DRY*, anneal the gold by holding the crucible over a bunsen burner. The gold will turn from a dark color to bright yellow. If the gold wasn't dry, it will spit out of the crucible. Set the crucible on a dry insulator (like a brick) to cool. If you place it on a metal surface, the crucible will likely break.

9.measure the left over of the gold and divide /primary sample
[for example leftover=0.15203 divide by 0.25000 =0.608‰
that means 608/1000 pureness
When cool, dump the gold onto a tared weighing paper or boat on the scale, weigh it to 4 decimal places, and calculate the results. Make sure you get any stray gold specks.

I use the same procedure for pure gold, although the "Mint" procedure given would give more accuracy on the final digit. In this case, triplicate samples (or, more) would be best. For the pure gold, they used .45 grams of silver, still maintaining the 2.25 to 1 ratio.

why is that i use for assay of karat gold 0.25gram Gold and 0.32gr silver
while for FINE GOLD 0.25gram gold + 0.32 silver + 0.05 Copper
I don't know why they add the copper, although I have seen it in the "Mint" procedures. They surely have a reason for it. I don't use it

Hope this helps.


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## Noxx (Dec 20, 2008)

That's a great description  Maybe it could be added to the wiki...


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## qst42know (Dec 20, 2008)

GSP 

You should sticky this to the top of the section you decide to leave this in so it is easy to find.

Done!

Harold


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## masarh (Dec 24, 2008)

on step 6) when rolling, i have rolling mill since my primary business is jewellery production, but are there any spec. on how thin/thick should the sheet be?
since i am suspecting that MAYBE, the sheet is to thick and the Acids can not ETCH [remove the silver]??

on steps 6 and 7 when "Heating" /"Boiling" in Acid
also i am suspecting that MAYBE, the 'faltened sheet' is not heated enought and i have to wait to boil?

how true it is that when heated with SECOND ACID, * 2 times, will remove/disolve all the silver left over.


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## masarh (Dec 24, 2008)

> why is that i use for assay of karat gold 0.25gram Gold and 0.32gr silver
> while for FINE GOLD 0.25gram gold + 0.32 silver + 0.05 Copper
> I don't know why they add the copper, although I have seen it in the "Mint" procedures. They surely have a reason for it. I don't use it


could it be that because of the low content of non-PM they add copper, so it can react with LEAD better and it smoke all the impurities and the lead during the cuppelation?


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## goldsilverpro (Dec 24, 2008)

Masarh,

In my books, I have several descriptions of the Mint method. All are somewhat different and only one mentions the thickness of the gold after rolling. T.K. Rose, in his 1937, 7th edition of "The Metallurgy of Gold," says the thickness should be 0.25 mm. I would think that if it were too thin, the gold would break up. If it were too thick, all of the silver would not dissolve when using a low Ag/Au ratio.

The bead is first flattened a bit, with a hammer, so the rolls will grab it. It is rolled into a long strip and then shaped into a cornet (a spiral) by hand. The portions of the spiral should not touch each other. The cornet is annealed at a dull red heat and then allowed to cool before parting. The rolls must be very clean with no oil.

I would first try the lower Ag/Au ratio of about 2.0 to 2.2, to prevent the gold from breaking up. Since you are rolling the bead, this ratio should work. To prove your process, assay some known 999.9 Fine gold. A Canadian Maple Leaf is a good source.

If the gold is about 70-80%, or better, slight amounts of silver will be retained in the gold. This is called a "surcharge". If the gold is of less purity, there will be a slight loss. I would suggest running 2 samples plus a "proof" sample, all run side by side. 

For karat gold. To make the proof sample, weigh some fine gold and add some copper. Use enough of each to approximate the composition (and quantities of metals) of the unknown samples that you are running. Then, correct the assay based on what happened to the proof

For refined gold, just use the proof gold alone.

None of the references I have add copper to a pure gold sample. I am thinking that the guy added copper to discolor (green) the cupel. I think that the copper would be the last thing to be oxidized and absorbed into the cupel. If so, the green color would be an indication that all of the lead has been absorbed into the cupel. I may be completely wrong about this.


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## qst42know (Dec 24, 2008)

The small amount of copper remains with the gold and silver in the button and aids in reducing the tendency of spitting and sprouting.

http://books.google.com/books?id=i_JMAAAAMAAJ&pg=PA267&lpg=PA267&dq=copper+in+mint+fire+assay&source=web&ots=fIrn5c6uqk&sig=DoDncrIdHESogL53NtOmoitLsDY&hl=en&sa=X&oi=book_result&resnum=5&ct=result


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## goldsilverpro (Dec 24, 2008)

Very good, qst. I stand corrected.

I can't imagine any spitting to occur at a 2/1 ratio, which I have never used, but perhaps it would. Spitting/sprouting can also be avoided by cooling the bead very slowly. I used to cover the cupel, very carefully, with a hot empty cupel (upside down), before removing it from the furnace, in order to cool the bead slowly. Even with pure silver, I rarely got sprouting. This is difficult with bone ash cupels because they tend to crumble. Although the bone ash cupels are the best, especially for silver, I usually used DFC composite cupels (bone ash + Portland cement, I think) due to their durability. For precision, I used bone ash.


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## qst42know (Dec 24, 2008)

This is from an early text (1913) written by the son of a Royal Mint Assayer and the technique may only be part of the handed down tradition rather than a having a firm basis in science. Later text may have dropped the use of copper for that reason.

It was also mentioned it aided malleability for rolling. 

I have read in a 1909 text that spitting is blamed on a contaminate in the cupel itself that reacts with the litharge. Calcium carbonate if I remember correctly?

This may be an old debate we have stumbled on based on where you learned your assaying from?


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## goldsilverpro (Dec 24, 2008)

I downloaded that book, awhile back, but haven't read it. I think I should.

Pure silver bars spit like crazy, especially if you melt them too hot.

In the late 60s, I went to work, in L.A., for Sel-Rex, a big scrap refiner and the largest supplier of gold plating systems in the world. At the time, they were located only on the East coast. Soon, they built a large refinery in L.A. and I was in on the ground floor, as their Senior Chemist. 

My boss was friends with the owner of a large, very famous fire assay lab in S.F. that had been around since the gold rush. It is no longer there and I don't remember the name. Anyway, I spent a week there in training and that's how I got the basics. Then, I got copies of Bugbee, and Shepherd and Dietrich, and Beamish, and Fulton and Sharwood , and started learning.

At the L.A. refinery, we had 2 large DFC gas assay furnaces and we usually ran from 72 to 144 assays per day. I trained an employee to do the assaying and I just filled in for him when he was on vacation. 

Since then, I have run fire assays for 40 years, in almost every place I worked or owned - at least 10,000 assays. Never as a business - only for our own deals. 

Once you learn it, it's like falling off a log.

My experience is about 95% in scrap, with only about 5% in ores. 

If you know exactly what a batch of material runs, it's hard to lose money on it. Of course, the other side of the coin is the art/science of sampling. A good assay on a non-representative sample is less than worthless. Good sampling is much more difficult than good assaying. 

Where did you pick up your assaying savvy, gst? It's obvious that you have a lot of knowledge.


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## qst42know (Dec 24, 2008)

I learned from a 1909 copy of Fulton. 

Mostly just as a hobby before I knew anything of making my own chemicals. I had always thought the chemicals were unobtainable without a business. I had used the fire assay techniques for a crude refining of silver contacts and some gold plated stuff. Using a propane torch and kiln bricks. I would guess I have run hundreds of assays none technical or professionally.

I learned a lot making my own cupels from roasted bone meal and larger ones from straight Portland cement.

The Portland cement cupels do sometimes spit with only the melting of lead. I got in the habit of starting with the lead, the cupels that spit would be roasted until they calmed down then I could add the silver.

I have experienced the pure silver sprouting long antlers spitting off sizable pieces, and sometimes the whole bead would crystallize entirely looking much like a head of cauliflower. I never did figure that one out but I wish I would have saved one to see what you thought of it.


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## Lou (Dec 24, 2008)

goldsilverpro said:


> If you know exactly what a batch of material runs, it's hard to lose money on it. Of course, the other side of the coin is the art/science of sampling. A good assay on a non-representative sample is less than worthless. Good sampling is much more difficult than good assaying.




This is a take home message and clearly he who said it knows what analysis is all about. Proper acquisition and handling of a sample is imperative or an assay isn't worth the paper it is printed on let alone the big money that probably rides on it. This is true for almost every type of test--an XRF on an improperly prepared sample may also be worthless (this is a notorious example).


When one starts dealing with UHP metals and doing analysis on them, even very small things start to accrue and throw off the results. A case example is rolling out a sample--your sample will pick up metal off the rollers, or perhaps even grease. Even handling a sample with your bare hands can lead to measurement errors (fingerprints have mass). Go even further and for more precision and temperature, humidity, and pressure fluctuations will affect your balance's performance. Most of the new Cahn or Sartorius microanalytical balances have multiprocessors that correct for the such variables through sophisticated algorithms. 

Analytical chemistry can be taken as far as one wishes to take it, it's all what you want to settle for accuracy and precision-wise. 


I love seeing this type of discussion on the forum. I think it is very important that members here understand that there's no magic to an assay. Knowing what happens to your sample when sent out for an assay is key to understanding what your assay means and how to value it.

Everyone willing, I think we should make various threads about assay methodologies--one dedicated to traditional fire assays, one to alternative fire assay, and perhaps one directed towards instrumentation. I'd love to discuss XRF, ICP, EDX, and AA at length and how they pertain to the precious metals if there is enough interest. 

I've some time off this week obviously, so I'm probably going to make some value posts soon . Next I think will be proper sample preparation.

Merry Christmas all,

Lou


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## Oz (Dec 25, 2008)

Well Lou you have talked to me before about operator error with XRF. If my vote counts for anything I would love to hear you outline proper procedure for this. Although the cost of such equipment is beyond the means of the majority of this forum many accept XRF as the holy grail of testing. If they understand the process thoroughly they will be in a position to judge if the operator giving results truly knows how to use his equipment.

There are those out there that have the money for this equipment, but have no clue.


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## masarh (Dec 25, 2008)

Noxx said:


> It will work. But I'm not sure about the accuracy though.
> 
> Why do you wrap your metals in lead foil ? Also, you should mention to use pure metals to inquart.



why should there be used PURE metals, when they will dissolve and/or 'smoke'?


lead collects all other non precious metals, while being heated in cuppellation furnance, thats why you need lead foil.


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## masarh (Dec 25, 2008)

qst42know said:


> It was also mentioned it aided malleability for rolling.



this couldnt be true, since the easiest and the best gold that melts is that of high gold content like 90% or more.


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## qst42know (Dec 25, 2008)

This could be true. 

Assays are performed when the total alloy is questionable. If the starting gold had traces of Antimony or Arsenic they could be very brittle. Traces of some metals will pass the fire portion of the assay and must be removed in the parting step.

I could not find a specific reference to support this but copper may help keep your rolled cornet in one piece for parting. When your sample tears in rolling there is always a possibility small crumbs could be lost spoiling the accuracy of the assay.


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## qst42know (Dec 25, 2008)

This text points to other elements that add brittleness to PMs. One of particular note is lead where 1 part in 500,000 can have a noticable effect.

http://books.google.com/books?id=2SpVAAAAMAAJ&pg=PA66&lpg=PA66&dq=brittle+alloys+of+gold+and+silver&source=web&ots=UPLgvztUbl&sig=8Q19PU5hCOJt5ZuBBpwQs8hToGA&hl=en&sa=X&oi=book_result&resnum=1&ct=result#PPA66,M1


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## goldsilverpro (Dec 25, 2008)

> why should there be used PURE metals, when they will dissolve and/or 'smoke'?
> 
> lead collects all other non precious metals, while being heated in cuppellation furnance, thats why you need lead foil.
> 
> this couldnt be true, since the easiest and the best gold that melts is that of high gold content like 90% or more.



You are right. Superpure metals are not necessary for inquartation. However, the silver used should be of decent quality and you should avoid such contaminates as tin, since it would only complicate the process.

The lead foil alloys the silver and gold and helps to drag the base metals into the cupel. To prepare for parting, some people alloy the Au and Ag with a torch, skipping the cupellation altogether. This is a poor practice. There can be losses and the base metals are still in the alloy, some of which can be retained in the final gold.

Concerning the increased malleability, qst was quoting the book that he gave a link for. Your argument is with Ernest Alfred Smith and not with qst.

*Lou,*

Although the handling of samples, after you get them, is extremely important, I was talking about the OBTAINING of the samples, in the first place. In other words, if a guy wants to sell you a pile of mixed scrap, how do you pull representative samples from that pile that will allow you to determine the value of the entire pile. You can guess and bid low but, even then, you can be bitten. The reason I said that a good assay on a bad sample is less than worthless, is because a high sample will lose money and a low sample can cause you to miss the deal. Each deal is different. Good sampling requires knowledge, ingenuity, and some math - although not absolutely required, a little knowledge of statistics can be very helpful.

Here's a few situations that I have found myself in:

(1) A company I worked for generated 50 drums of silver bearing slag every few months. They shipped it to be refined. The refiner processed a 5% sample, taken here and there, and gave my boss the results. He had suspected of being cheated for some time. To keep the refiner honest, I was given the chore of sampling the material and then determining the value. The questions I had to ask were: How do I pull the samples? How many samples (and their size) do I pull to get decent statistical results? How do I process the samples?

(2) A guy brings in a 100 oz bar of mixed karat gold that he had melted. The bar has some slag on it and there are a few magnetic objects embedded in it. We want to buy it and he is willing to let us sample it in any way that we want. He wants 95% of the gold value, which we agree to. However, unless we do things right, 95% is pretty tight. How do we sample the bar, in order to determine the value with less than a 1/4% error?

(3) A guy brings us 6 drums of mixed gold pins. They have been out in the rain and the drums contain water. There are leaves and other trash in the drums. He is willing to hang around until we get numbers. How do we sample the material?

(4) We went to a Ma Bell auction viewing somewhere in OR or WA. The lot we were interested in was 750,000# of mixed electronic scrap. In general, it looked pretty good. It was winter and the stuff had been sitting out in the weather. They allowed the bidders to pull samples as they required. How should we sample the material? No matter how we did it, it would only be an half-assed approximation. After we ran the samples, how should we bid the lot? BTW, we didn't get the deal.

(5) A scrapper brings us a pickup load of mixed boards. He agrees to leave them with us until we evaluate them. He says they are worth $10/#, but he's only guessing and is also jacking up the value. How do we evaluate them?

I could go on and on.


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## qst42know (Dec 25, 2008)

Noxx said:


> Why do you wrap your metals in lead foil ?



Lead foil is a convenient way to package your gold drilling's and measured snippets of silver to the preheated cupel. The samples are wrapped in lead tamped snug and are ready to drop. There are devices that will drop several samples simultaneously. They are pricey but if you are doing many assay samples at once this is the way to go.

http://www.lmine.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=17850&Category_Code=lead_loader&Product_Count=0


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## qst42know (Dec 25, 2008)

This post bugged me from the first time I read it. If anyone had paid attention to this post it would have been obvious where the source of the error was.

This member had stated he had selected samples from the material delivered to him that showed colors and had sent his selections out for assay. He did nothing to homogenize the bulk to a representative sample. His selections would be much like reaching into a ten pound bag of mixed coins selecting only dollars and presuming the whole lot contained only dollars.

The resulting g/ton meant nothing because he did not sample by the ton. 

No one should have been astounded by the resulting assay as he stated the error up front. A purely random sample of a homogenized mix should have been selected for assay. Not a cherry picked batch of stones that showed colors.

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=2596&start=0&postdays=0&postorder=asc&highlight=


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## Lou (Dec 25, 2008)

GSP,

I understood what you meant, I didn't miss the point  I was just going on further to say that handling is just as important as the actual sampling. 

You gave excellent examples. It is necessary to make sure one's representative sample is from a homogeneous source.

This problem with obtaining homogeneity is particularly bothersome with assaying melt samples. If metals aren't stirred properly, then there can be stratification, especially in the resulting casting (case example being high lead brasses). Induction melting greatly reduces this issue because it is self stirring.

@qst24know, great catch.


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## goldsilverpro (Dec 26, 2008)

In many cases, it is impossible to make the pile homogeneous. In the examples I gave, the bar (2) can be made quite homogeneous. The pins (3) can be made fairly homogeneous by drying and then by coning and quartering. The slag (1) can be made homogeneous (sort of), by coning and quartering, but if would require a helluva a lot of labor (grinding would be great, if you have the equipment). The rest cannot. So, you have to do the best you can. You basically pull several preliminary samples, intelligently, usually with some pre-processing (drying, blending, grinding, sorting, etc.), and assay them. Then, based on the results, you can use statistical formulae to estimate the full number of samples needed and how large they need to be, in order for the results to fall within the desired standard deviation level. You then pull the samples, assay them, and compute the std.dev. You may have to do it all over again, with help from the previous results. One time, we fire assayed 96 samples on a lot of several tons of pulps - the ground ash from the burning of circuit boards - before we got it right. Of course, the size and value of the lot has a lot to do with how much labor and equipment you put into it. I didn't put much into the pickup load of boards.

He who best knows the material always ends up the winner! 

Sampling ain't easy.


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## qst42know (Dec 26, 2008)

goldsilverpro said:


> He who best knows the material always ends up the winner!



Have you considered the folks who *won* the bid for the telecommunication equipment in your example 4 may have lost money on the deal.

Perhaps the phrase should be:

He who best knows the material doesn't lose!


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## goldsilverpro (Dec 26, 2008)

> He who best knows the material doesn't lose!



That's true, but it's like a game and it's always a downer to not get the material. On that lot, we were probably better not getting it, even if it was free. There was a lot of junk in it. The transportation, sorting, burning, melting, etc. could have eaten our lunch. We really didn't bid much on it.


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## qst42know (Dec 26, 2008)

I'm guessing you knew the material best.

I've been in the auction game for some time now and it's often better to come home empty handed than with something you paid too much for.


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## Anonymous (Feb 9, 2010)

I did melts & assay for years on 47th street. The first step is do your own melt to make sure it's a homogenius material, don't accept anyone elses melt. When drilling make sure the bar is clean, because borax or dirt on the surface of the bar will kill the assay. At this point an analitical scale is most important, mine is acurate to 1/10,000 gram & that's OK but not great. 
measure the samples like you wrote. The big buyer does two samples & takes the lowest of the two, that's business. The corect way is to do 3 samples and averidge the three. if one sample is widely divergent, throw it out and averidge the two that should be exact on the first three didgets and close on the fourth.
Use CP grade nitric and fine silver and wrap the sample in 20 times it's weight in a led sheet. Most of the rest of what you wrote is fine. when preparing the oven for the bone ash cupels put a layer of spent cupels in the front of the oven to guard the cupels you're using. you have to open the door to check the 3 samples. The led will cary all but gold, silver, and paladium or platinum into the lambs bone ash cupel. 
At the end you may see something that looks like colors over the tiny ball of metal in the coupel. The ball should be round and clean when taken out of the oven. If it's round but seems to have indentations in it, it's probably paladium. 
next step is to put it through a mill and make it paper thin. now you simmer 3 dishes of CP nitric. important not to put the sheets in the nitric untill the acid is hot, because if it has paladium in it you won't get it out. 
After the first acid, pour off the acid carefully and wash it in distilled water. Then I put a paper napkin away from the sample to absorbe the water.
repeat this with a second acid and distilled water again. 
Now it should hold together well and can be slowly heated and dried.
now that you have begining weights of the three samples (kept in order) weigh again for finished weight. Now read bugbee on fire assay. 
I've enjoyed reading, now I hope I've contributed.
Best Regards, Carmine


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## lazersteve (Feb 9, 2010)

Carmine,

Excellent first post!

Welcome to the forum.

Do you have any tips for assaying Platinum and mixed PGMs?

Steve


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## Anonymous (Feb 13, 2010)

I worked buying scrap, doing melts & assay for a business who did between 200 and $300,000.00 per week on 47th street in New York. This started in 1979 and went on a little over 5 years. Then the major partner & spark in the business died of cancer, & the business died. I assayed gold & silver that I melted for the business. First we did a mathmatical probability by multiplying total 14K bought in by 0.57, 10K by 0.39, & 18K by 0.729 to get a realistic figure of minimum gold that should come out of the assay. Then every night the assay had to be done & called in before second Lundon fix. Just multiply the assay by the weight of the bar to get the fine gold content of the bar. 
Silver assay is realy easy. I melted scrap silver & monigramed silver into bars that were usually about 27 pounds. I cleaned off all borax with a hammer & a metal brush. I then took two drillings from the top of the bar & two from the bottom. I used a heavier sample, don't add anything to the silver.& wrapped it in 20 times it's weight in led. same process with the coupel & getting the tiny ball of metal in the coupel. at this point if you're sure about the metal you put in the bar, you can put second weight over the starting weight. If there's any chance of gold in it, go on to boiling it out in the two CP nitric acid solutions. Then it's simple math to determine gold & silver content.


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## 4metals (Feb 13, 2010)

Carmine,

Silver likes to spit, what kind of proofs did you run?


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## goldnugget77 (Feb 17, 2010)

[quoteSilver assay is realy easy. I melted scrap silver & monigramed silver into bars that were usually about 27 pounds. I cleaned off all borax with a hammer & a metal brush. I then took two drillings from the top of the bar & two from the bottom. I used a heavier sample, don't add anything to the silver.& wrapped it in 20 times it's weight in led. same process with the coupel & getting the tiny ball of metal in the coupel. at this point if you're sure about the metal you put in the bar, you can put second weight over the starting weight. If there's any chance of gold in it, go on to boiling it out in the two CP nitric acid solutions. Then it's simple math to determine gold & silver content.][/quote]

If there was gold in the sample
If you disslove in CP nitric acid solutions
the silver will go into the acid then you will have to precipitate.
I am confused


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## 4metals (Feb 17, 2010)

The silver content is calculated by weighing the bead from cupellation, as no silver has been added. If you suspect gold, part the silver bead and weigh the gold that is insoluble.


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## goldnugget77 (Feb 18, 2010)

Hi 4metals
Thanks for your answer 
I was wondering what you would do in this case if you suspected 
platinum ,palladium and iridium


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## 4metals (Feb 19, 2010)

Platinum may or may not digest in the silver depending on how much is in the sample, the palladium will be in with the silver and the iridium will be on the bottom with the gold. That is one reason you anneal the gold after parting as any Pt, Ir, or Ru will be visible because it will appear as dark spots.


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## Anonymous (Feb 21, 2010)

Hi again. You're right about silver spitting, most often with a torch & uneven heat or when overheated. You're using a kiln and hopefully putting spent coupels in front of the ones you're using. This is to try to maintain an even heat when checking the sample to see when they are done. Bugbee on fire assay writes to use 3 samples. if one of the samples is widely divergent and the other two are the same on the first three numbers after the decemil, you averidge two and throw out the third. They should all be same on the first three numbers and very close on the fourth so not using a sample should be a rare ocurance. For platinum group metals in the sample, you have to closely examine the little ball in the coupel when the oven cools. gold amd silver have melting points that are close. Platinum group metals need a great deal more heat to melt. If the ball has only silver or silver and gold it will be smooth. If the ball has platinum group metals, it's still round but it looks kind of like craters on the moon at close examination. Assaying a sample of a bar you didn't melt is foolish. You should have a good idea of what went in so you know what to expect, and that it's realy homogeneous melt. If the sample has a little paladium it can come out in a single acid (cp nitric). The trick is to heat the three dishes of acid to a simer and then put in the the 3 paper thin pieces of metal. if the acid isn't hot when the metal is put in, paladium won't come out in the acid.


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## 4metals (Feb 21, 2010)

Carmine,

The row of cupels does help keep the temperature more constant but I always teach assayers to run a proof as well. 

The palladium in silver not parting is a neat trick, but to collect Pd to pay on it's better for the buyer than the seller. Still you have to digest the gold and drop the Pd with DMG.


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## HAuCl4 (Aug 18, 2010)

Once upon a time our "cupellation furnace" broke (the electric resistance type), and we performed 5 fire assays (one at a time) for bullion with an oxy-acetylene torch borrowed from a jeweler next door, a cupel each, and 4 firebricks. When the results came back within 0.0001 for all the 5 assays, (surprise!) versus what the clients had from other refiners, I started to think: The precision balance is the only expensive piece that I really need.

The process used was similar to what is described by GSP as the "Mint method", except we used a manual roll for the beads => cornets, annealing in between rolls.

Is there a way to make a precision bullion assay without an analytical balance?. Something suitable to take in the field, outside the lab?.

I thought I'd ask.

edit: The samples we used were always 0.5 grams instead of 0.25 grams, although at the beginning we used 1 gram samples in larger cupels.


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## goldsilverpro (Aug 18, 2010)

HAuCl4 said:


> Once upon a time our "cupellation furnace" broke (the electric resistance type), and we performed 5 fire assays (one at a time) for bullion with an oxy-acetylene torch borrowed from a jeweler next door, a cupel each, and 4 firebricks. When the results came back within 0.0001 for all the 5 assays, (surprise!) versus what the clients had from other refiners, I started to think: The precision balance is the only expensive piece that I really need.



I've know guys who did this. Although I have no data to back it up, I would never trust the results. One problem is that you are relying on the nitric acid to remove 100% of all the impurities rather than absorbing them into the cupel. With certain impurities, this might be a problem. 



> Is there a way to make a precision bullion assay without an analytical balance?. Something suitable to take in the field, outside the lab?



No way that I know of. You have to weigh both the sample and the final gold very precisely. The precision of the weighing determines the precision of the assay. As a minimum, I would want to weigh to 4 decimal places - .0001 g. I actually prefer 5 places - .00001 g. 

Let's say you used a .001 g scale and the gold weighed .250 g. The last digit is questionable. Therefore, the weight is actually somewhere between .249g and .251g. The error could be +/- 0.4%. If that represents 100 oz of gold, the value would be questionable to the tune of +/- $480. Not good enough for me. With a .0001g scale, that is reduced to +/- $48.

Hope my math is right.

Action Mining has a Mickey Mouse chart composed of a bunch of different sized circles with corresponding weights. You "weigh" the bead by placing it on the circles until you find one that fits. Very inaccurate.


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## HAuCl4 (Aug 18, 2010)

I don't know how to do it without an analytical balance either GSP.

We were buying at 3% discount, so really the torch assays were more of a safety thing. We generally paid the client what he had in the assays even if it was a little richer than our assays. I didn't expect them to be that accurate, maybe because it was just gold and silver and little else?.

Our balance was 0.0001 gr accuracy. The other day I was checking balances out and I found a microgram balance for the price we paid for our 0.0001 back in the day!.


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## 4metals (Aug 18, 2010)

I am amazed at the way the prices of electronic balances have come down over the years. But then again the first balance I used in college was a chain o matic.

http://www.antiquesimagearchive.com/items/275935.html

They don't make 'em like they used to!


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## goldsilverpro (Aug 18, 2010)

4metals said:


> I am amazed at the way the prices of electronic balances have come down over the years. But then again the first balance I used in college was a chain o matic.
> 
> http://www.antiquesimagearchive.com/items/275935.html
> 
> They don't make 'em like they used to!



A Becker Chain-O-Matic was my first balance also.


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## HAuCl4 (Aug 19, 2010)

It took me forever to make a measurement in one of those mechanical things. We bought a Sartorius balance for $7,800, it was digital and self-calibrating and 0.0001 readability. Much faster. You can get a microgram balance for that amount of $ these days. Unthinkable at the time.

To this date, it is the one expensive item in assaying/refining that I would still have to buy.

Edit: If you are really looking around, it is amazing how many of the items needed in a lab can have a very affordable source. See picture and guess what it is and how it can be used?. :lol:

Most of the other items can also be easily sourced/replaced with everyday items. The one notable exception being the analytical balance.

The only relatively cheaper solution to the balance "problem" is to take a 10x larger sample, but then you need oversize cupels, a lot more lead, more acid, and a lot more time "rolling the button". Not an elegant solution, since you still need a 0.001 gr balance at a minimum.


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## 4metals (Aug 19, 2010)

That would be a porcelain casserole used for parting and annealing.

You can try auctions if you're looking for an analytical balance, I usually go to the auction site on the day of the inspections with some of my calibration weights and make sure the balance I want to bid on is working. With the internet today it's easy to find out about the auctions and most sites list all of the items for sale and give descriptions. If you like what you see, and the auction is close enough, go and bid.


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## HAuCl4 (Aug 19, 2010)

4metals said:


> That would be a porcelain casserole used for parting and annealing.
> 
> You can try auctions if you're looking for an analytical balance, I usually go to the auction site on the day of the inspections with some of my calibration weights and make sure the balance I want to bid on is working. With the internet today it's easy to find out about the auctions and most sites list all of the items for sale and give descriptions. If you like what you see, and the auction is close enough, go and bid.



You mean for the mechanical ones 4metals or the digital ones?. I live outside the US, but I would certainly purchase one of the "antiques" for sentimental value if it was in good shape. Where can I get good and precise calibration weights?.

If it was for work, I'd go with a 0.0001 gr digital ones for about $1,500-$2,000. Even amazon has them.

The picture is of a [email protected] porcelain coffee cup, and yes I used similar ones for annealing and parting. Much cheaper and sturdier than equivalent labware. Got a dozen for the price of one parting crucible...and my wife likes them too!. :lol:

I'm going to be in Miami-Orlando next month, and I also want to purchase about 5 OZ of gold, or scrap, or coins, and pay near spot with personal credit card. Anyone know how to do this?.


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## 4metals (Aug 19, 2010)

The digital ones, I got a Sartorius CPA 64 balance sensitive to 0.0001 gram at an auction in February for $75.


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## HAuCl4 (Aug 19, 2010)

4metals said:


> The digital ones, I got a Sartorius CPA 64 balance sensitive to 0.0001 gram at an auction in February for $75.




Wow!. I can pay you $100 right now for it!. Think about it: 25% profit!. :lol:


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## goldsilverpro (Aug 19, 2010)

Here's a Sartorius for $900.
http://balance.balances.com/scales/559

I would also get a furnace for cupelling. You can get an adequate electric burn-out from a jewelry supplier for a few hundred $.


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## HAuCl4 (Aug 19, 2010)

Great tips guys, thanks!. Anyone can become a refiner!. Gotta find the gold now!.


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## 4metals (Aug 19, 2010)

Anyone who comes to this site and learns. We have essentially lowered the bar.


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## HAuCl4 (Aug 19, 2010)

4metals said:


> Anyone who comes to this site and learns. We have essentially lowered the bar.



Any ideas on how to recover gold from seawater?. (Even at an economic loss). :?:


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## 4metals (Aug 19, 2010)

That has classically been like chasing your tail, as a general rule if you can't get a positive stannous test it's not worth the effort.

I wonder which side of a membrane (RO) the gold ends up on? I wonder if any salt mines have assayed their salt for PM's? If all of the oceans of the world have gold in solution, than the pre-historic remnants, or salt mines, should be holding concentrates from ancient seas.


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## HAuCl4 (Aug 19, 2010)

4metals said:


> That has classically been like chasing your tail, as a general rule if you can't get a positive stannous test it's not worth the effort.
> 
> I wonder which side of a membrane (RO) the gold ends up on? I wonder if any salt mines have assayed their salt for PM's? If all of the oceans of the world have gold in solution, than the pre-historic remnants, or salt mines, should be holding concentrates from ancient seas.



Just imagine that gold is $1,000,000 an OZ, and give the problem to your subconscious. Let me know the answer by Private Message!.


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## HAuCl4 (Aug 20, 2010)

4metals said:


> That has classically been like chasing your tail, as a general rule if you can't get a positive stannous test it's not worth the effort.
> 
> I wonder which side of a membrane (RO) the gold ends up on? I wonder if any salt mines have assayed their salt for PM's? If all of the oceans of the world have gold in solution, than the pre-historic remnants, or salt mines, should be holding concentrates from ancient seas.



I was thinking that instead of a membrane one could try some "special" solvent extremely selective for gold in a reverse osmosis type of idea like this diagram. I don't know what other attempts have been made or in what direction. The pipe is say 1 Km long, and the "funnel" in the bottom, near the bottom of the sea has a very large area. The water pressure against the solvent frontier acting like a pressure filter. The solvent slowly circulates from the top down by some type of pump. Crazy idea?. I wonder if it can be calculated, and if there is a suitable solvent. Even if it isn't economically viable, going to the moon wasn't economically viable either. :?:


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## 4metals (Aug 20, 2010)

I've seen estimates of gold ranging between 0.1 and 2 milligrams per ton of seawater, that's in the parts per trillion range. Even with the perfect solvent, a tremendous amount of water would have to contact the solvent for it to collect even the smallest quantity of gold. It's just that the oceans are so big that makes the parts per trillion amount to something.

I think the only thing going for you in this case is the gold is already in solution. There's just sooooo much solution. :shock:


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## HAuCl4 (Aug 20, 2010)

Of course you are right. If you had told a miner 60 years ago that ore with less than a gram per ton could be exploited by heap leaching with cyanide, he would have laughed. A 0.1 microgram balance was unthinkable 25 years ago, today $7k, etc.

I read there have been serious (not scams) attempts on the gold seawater thing, but I do not know what process or technologies they failed with and how much they recovered, costs, etc. I have tried web search and have only come up with unreliable bits of info. 

I do not know even HOW to assay seawater for gold content!. Do you?.


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## Barren Realms 007 (Aug 20, 2010)

HAuCl4 said:


> Of course you are right. If you had told a miner 60 years ago that ore with less than a gram per ton could be exploited by heap leaching with cyanide, he would have laughed. A 0.1 microgram balance was unthinkable 25 years ago, today $7k, etc.
> 
> I read there have been serious (not scams) attempts on the gold seawater thing, but I do not know what process or technologies they failed with and how much they recovered, costs, etc. I have tried web search and have only come up with unreliable bits of info.
> 
> I do not know even HOW to assay seawater for gold content!. Do you?.




Evaporate the water and testthe remians.


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## Lou (Aug 20, 2010)

For assays of that very low concentration, it is done exclusively with ICP-MS after careful preconcentration of a sample.

The only way I could think to recover gold would be with some sort of very selective ion-exchange resin--with water passing over the resin by tidal power.


Lou


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## qst42know (Aug 20, 2010)

If you do figure this out there are places they are already paying to pump huge quantities of seawater. The desalination plant in Saudi Arabia, and a billion dollar desalination plant in Queensland, and any others in arid lands.

It would have to be something truely revolutionary though. I'm certain they have given the issue a great deal of thought already. :mrgreen:


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## 4metals (Aug 20, 2010)

> Evaporate the water and testthe remians.



Mother earth has done this for you already, go to a salt mine, that's an old ocean less the water. Probably concentrated 25 to 50 times already. The salt is more valuable than the gold it contains.


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## HAuCl4 (Aug 22, 2010)

Barren Realms 007 said:


> Evaporate the water and testthe remians.



Actually the idea of diluting more is what keeps hitting on me. I don't know why. :roll:

If they threw me in jail and only let me out if I paid in gold, I'd actually, at this point in time, choose mercury neutron bombardment, over claiming gold from seawater... One has been done successfully at high cost, the other, if anyone solved the problem, he is keeping it very quiet.

From wikipedia:

Gold synthesis from Mercury
Gold obtained by mining has copper and silver impurities. Gold of higher purity can be made through the photoneutron process:

Mercury 198 + 6.8MeV gamma ray 1 neutron + Mercury 197 (half-life 2.7 days Gold 197 + 1 positron)
These energy levels allow a more efficient neutron source than the Spallation Neutron Source.

[edit] Gold synthesis in an accelerator
Gold synthesis in a particle accelerator is possible in many ways. The Spallation Neutron Source has a liquid Mercury target that will be transmuted into Gold, Platinum, and Iridium, which are lower in atomic number.

[edit] Gold synthesis in a nuclear reactor
Gold was first synthesized from mercury by neutron bombardment in 1941, but the isotopes of gold produced were all radioactive[3].

Gold can currently be manufactured in a nuclear reactor by irradiation either of platinum or mercury. Since platinum is more expensive than gold, platinum is economically unsuitable as a raw material. Only the mercury isotope 196Hg, which occurs with a frequency of 0.15% in natural mercury, can be converted to gold by neutron capture, and following electron capture-decay into 197Au with slow neutrons


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## Barren Realms 007 (Aug 22, 2010)

HAuCl4 said:


> Barren Realms 007 said:
> 
> 
> > Evaporate the water and testthe remians.
> ...



Am I understanding you right that they can change the molecular structure of mercury to become gold just by irradiation bombardment?


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## HAuCl4 (Aug 22, 2010)

Not "molecular structure" but atomic number. Essentially making one element from another.


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## Barren Realms 007 (Aug 22, 2010)

I didn't phrase that right but you said what I ment. Change mercury to gold, interestng.


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## goldsilverpro (Aug 22, 2010)

If one owned a large nuclear reactor, they might be able to produce a gram a year. We need a Pie-In-The-Sky or If-Pigs-Could-Fly category.


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## jimdoc (Aug 22, 2010)

goldsilverpro said:


> We need a Pie-In-The-Sky or If-Pigs-Could-Fly category.




Pigs can fly, I saw it myself at a Pink Floyd concert.

Jim


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## Barren Realms 007 (Aug 22, 2010)

goldsilverpro said:


> If one owned a large nuclear reactor, they might be able to produce a gram a year. We need a Pie-In-The-Sky or If-Pigs-Could-Fly category.



They can borrow my dunce hat. :roll:


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## HAuCl4 (Aug 22, 2010)

goldsilverpro said:


> If one owned a large nuclear reactor, they might be able to produce a gram a year. We need a Pie-In-The-Sky or If-Pigs-Could-Fly category.



I once saw a plane full of pigs take off.


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## Barren Realms 007 (Aug 22, 2010)

HAuCl4 said:


> goldsilverpro said:
> 
> 
> > If one owned a large nuclear reactor, they might be able to produce a gram a year. We need a Pie-In-The-Sky or If-Pigs-Could-Fly category.
> ...



Those were my pigs. I wondered where they went to. 8)


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## talalstuvs (Oct 7, 2010)

masarh said:


> i am writing this procedure as i was told but i need some explanation [if any]
> 
> ASSAYING KARAT GOLD
> 1.drill sample from bullion,
> ...



I try your procedure about fine gold but its not work i don't know why .
I use 68% nitic . Silver and copper not disolve i boil them 4 time but there isn't any kind of chage they are same. I use fire assay. what could be fault ?

1. 0.075 gold
2. 0.058 silver
3.0.037 copper
For 1st acid ration is 1part water and 1 part nitic acid and for second and third acid i use 68% nitirc .
could you tell me why it's not work ?
waiting for ur reply.


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## HAuCl4 (Oct 7, 2010)

You must use more silver. You have too much gold in % in your button. why make such small samples??? :shock: 

Re-read the instructions and follow them to the letter is my suggestion.


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## talalstuvs (Oct 7, 2010)

HAuCl4 said:


> You must use more silver. You have too much gold in % in your button. why make such small samples??? :shock:
> 
> Re-read the instructions and follow them to the letter is my suggestion.



I always use same ratio in 18 and 22 karat gold but i dont mix copper i use 
1) .075 gold
2) .118 to .120 silver
its worked. But when i use same ratio for fine gold there always some diffrene in two sample why is it ?


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## HAuCl4 (Oct 7, 2010)

talalstuvs said:


> HAuCl4 said:
> 
> 
> > You must use more silver. You have too much gold in % in your button. why make such small samples??? :shock:
> ...



You must use more silver. You have too much gold in % in your button. why make such small samples??? 

Re-read the instructions and follow them to the letter is my suggestion.


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## goldsilverpro (Oct 7, 2010)

talalstuvs said:


> masarh said:
> 
> 
> > i am writing this procedure as i was told but i need some explanation [if any]
> ...


The copper is added to the fine gold sample (although, I think 20% Cu is excessive) to assist driving all of the lead into the cupel and to help make the bead easier to roll without cracking. The karat gold already contains copper so it is not necessary to add any.

A ratio of silver to gold should be between 2:1 and 3:1 and the bead should be rolled out to about 0.01" (.004 cm) thick, or less. If the ratio is less than 2:1, silver will most probably be retained in the gold and the results will be high. If greater than 3:1, the gold will tend to break up and there will be a possibility of losing small pieces when pouring off the nitric and the rinses. I prefer at least a 3:1 ratio (actually, I use about 5:1), in order to insure that I have removed all of the silver/copper. However, since my technique precludes the possibility of losses, I can tolerate a higher ratio. Also, with the high ratio (5:1), I don't worry about rolling it thin. I just flatten the bead out with a hammer.

In the instructions above, if you were assaying 18K gold, with a sample of .25g and an addition of .32g of silver, the silver+copper/gold ratio would be 2.04:1, which is border-line. If it were 22K, the ratio would only be 1.48:1, which is way too low. With this ratio, I doubt if any of the silver would dissolve.

If the Ag/Au ratio is too low or, if the ratio is about 2:1 and the gold isn't rolled thin enough, you will get high answers. Also, you will most likely get variations between samples.


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## goldsilverpro (Oct 7, 2010)

talalstuvs,



> I always use same ratio in 18 and 22 karat gold but i dont mix copper i use
> 1) .075 gold
> 2) .118 to .120 silver
> its worked. But when i use same ratio for fine gold there always some diffrence in two sample why is it ?



With 18K, your ratio is 2.4:1. With 22K, it is 1.8:1. With 18K, you might be all right, assuming you rolled the bead thin enough. With 22K, at that ratio, I doubt if you'll ever get a right answer. Have you tried making up combining the right amounts of Au, Cu, and Ag, using those weight and ratio numbers, and assaying it? That should be done, along with the samples, as a matter of course, anyway. I would be interested in the results.

I think the reason you're getting differences in the samples is because (a) not enough silver, (b) the bead is not thin enough, or (c) you're not spending enough time in the acid(s). Possibly, it's all 3

If you only have a 4 place balance, I would use at least a .25g sample. A .50g sample for karat gold is traditional but some people only use .25. I've never heard of anyone using .075g. It's not good practice. Inaccurate assays can be very expensive. Don't cut corners.


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## talalstuvs (Mar 16, 2011)

could anyone send me video link of Assaying gold karat ? plz


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## Barren Realms 007 (Mar 16, 2011)

talalstuvs said:


> could anyone send me video link of Assaying gold karat ? plz



You can do a search on youtube and fine them.


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## talalstuvs (May 9, 2011)

How much I should preheat furnace for .100 milegram and how much silver
I should use after placing foil in cupel how much I should wait for it melting 
waiting for your replay .


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## 4metals (May 10, 2011)

That discusses read the methods are in this thread but another that covers it is this one.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=41&t=4789

Scale down the weights given proportionally to your sample size. Temperatures remain the same.


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## talalstuvs (May 19, 2011)

salam now i am using of .125 sample adding .125*2 silver and 3 part of foil lead .125*3 and i set furnace to 1100c but i am not getting button shap good and as i try to roll it its get break from side wht should i do sir ?


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## 4metals (May 19, 2011)

Try lowering the temp to 950 C and adding 2.5 silver. If the sample falls apart on rolling after cupellation, did it fall apart or split apart like this
when you rolled it before assaying? I would add 4 or 5 times the sample weight of lead as 3 times is probably not enough.


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## talalstuvs (May 20, 2011)

Is there any kind of accurate weight for foil lead for sample wait or not ? someome told me should take 3 part foil lead. means to saying is if sample is .250 then foil lead should be .250*3=750 and silver should be 2 part of ur sample weight .250*2=500 to not breaking for sample. is this ration is currect ? i try this method but still it break up .


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## 4metals (May 20, 2011)

What is the material you are assaying? 

I assay karat gold using a sample size of 0.5 grams and I cupel them in 15 gram lead boats. As long as the cupel is large enough to absorb the weight of lead you are using the cupellation will continue absorbing the lead and base metals into the cupel. 

Are you annealing the beads before rolling them?


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## talalstuvs (May 21, 2011)

4metals said:


> What is the material you are assaying?
> 
> I assay karat gold using a sample size of 0.5 grams and I cupel them in 15 gram lead boats. As long as the cupel is large enough to absorb the weight of lead yo
> u are using the cupellation will continue absorbing the lead and base metals into the cupel.
> ...


 

salam 
yes i annealing bead before rolling . how much gold, silver and foil i should use for not breaking gold ? less quality plz


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## talalstuvs (Jun 24, 2011)

Hi
In the procedure its use .250 mg sample and .320 pure silver.Now in day silver is quite expensive could i use .125 mg gold and .160 pure silver for 18 karat and pure gold to not breaking my gold. If .250 for accurate weight then i have 6 decimal scal. And also if i set my furance temp to 960 c how much time does it take to melt samples ? I tried 1100c its take 5 to 10 mints but sample sometimes spark . Now what should i do ? waiting for reply.


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## Westerngs (Dec 9, 2011)

The reason to add small amount of copper to sample to be cupelled is that lead (oxide) is absorbed by the cupel before copper (oxide) so when cupellation is complete there may be small amounts of copper in the button but no lead.

The reason you don't want lead in the button is that it causes cracking when rolling out the bead (If the button cracks enough, you may lose sample). Copper does not.

Finally, someone asked if the gold is pure after the assay process. Almost always not. There will be some silver retained depending on how well the process is carried out it can range between 0.1% to 1% of the final weight. For most accurate results follow goldsilverpro's suggestion of running a proof sample for correction purposes. The closer the proof sample is in composition or gold content to the sample, the more accurate the correction.


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## zachy (Dec 25, 2017)

as it should be the analysis of golden gold, for low grades and how to avoid the contamination of personnel with lead


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## rickzeien (Jan 15, 2018)

I really appreciate having access to this discussion and all the others here on this forum. 

It is many lifetimes of practical experience that simply would not be available in any other way. 

Thanks to all who have commented.

Sent from my LG-H872 using Tapatalk


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## zachy (Sep 30, 2019)

No one knows how to avoid contamination of leaded personnel, apart from the use of extractors and masks, what more safety measures can be taken?


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## DylanDownright84 (Jul 7, 2020)

Its official, I'm a GRF addict.


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