Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Best & Easiest way to refine gold dust to 99.9% purity
I feel like I need to tell whoever needs to know. This community you have built here is amazing. Here's an example: I have been wondering for months now what is the best way to clean gold I have found plaster gold. I learned something that is was very important knowledge just by reading a Comment. Great job again whoever needs to know. Thanks I should share that.
- Haleyville Alabama
May 14, 2024
Ed. note: Many readers have contributed to this discussion over many years, probably not realizing how helpful they have been. Thank you for the kind thoughts.
'Placer' not 'plaster'?
- Howe, Oklahoma
August 25, 2024
⇩ Related postings, oldest first ⇩
Q. Hello Experts;
I have just started to venture and little money in gold business, but I'm nowhere related to gold and chemicals. I have searched the internet and I came to know a lot about Aqua Regia Method and few steps on how to refine gold. But the steps and the vocabulary is too difficult for me to understand. 'I'm familiar with acid names. But all I would like to learn is or get a detailed, simple, easy and best procedure to refine Gold Dust to get 99.99% gold. I will be experimenting with small quantity at home so that I get to know how it is done and practice to get better results. Please experts, I will be highly grateful to you if can help me and tell me in simple words, step by step procedure to get 99.9% purity.
Regards
Mohsin Iqbal
- Dubai, UAE
2005
A. Burn the dust at 650 °C temperature.
Sieve it and remove iron by magnet.
Take 1 kg fine dust in 5 l glass beaker; add 1.5 l aqua regia (1 part HNO3 & 3 part HCl) in it very slowly. Boil the solution up to 30 min., then cool the solution and then filter by using Buchner funnel.
Add urea water & FeSO4 into your filtered solution until green colour reaches dark black colour. Settle the solution for 1 hour, then decant the solution into another drum. Remove the brown powder in a beaker. Wash it very well with HCl, and then wash with hot water until pH paper does not change.
Then dry that powder on heater slowly & melt at 1064 °C in melting furnace.
Bhupesh Mulik
jewellery - Mumbai, Maharashtra, India
Ed. note: Thanks for the highly detailed response, Bhupesh. Readers should be aware that these are hazardous operations and the instructions are intended only for people who have been trained in the safe handling of these dangerous materials.
Thank you for your explanation. I have flour gold and need to refine, but wasn't sure. I will do exactly as you described.
- St george Utah
June 18, 2024
Q. Hi,
I would like to know the reagent required to precipitate palladium.
Vidyadhar Sumant
- BOMBAY, India
2005
A. To Vidyadhar Sumant, you asked how to drop Pd from a solution. I assume a Pd Chloride solution that has been de- NOXed (HNO3 driven off and tested with starch-iodine paper) Pd Chloride will precipitate with Ammonium Hydroxide. As the pH rises to 7+ a pink precip called "magnus salt" will appear, as more NH4OH is added this will redissolve and around pH 7.5-8 depending on the temp of solution a bright yellow precipitate of NH3PdCl4 Ammonium Chloro Palladate. If you need to wash this on the funnel use cold concentrated ammonium chloride solution as NH3PdCl4 is somewhat soluble and you can have considerable metal loss if you don't know this. The "spent" solution also still has some metal left (around 1 gram in 10 liters), test it and do the math, is it worth the cost to recover, or concentrating? Good Luck.
Kiwi Bruce
- West Grove Pennsylvania
October 17, 2009
Q. Is there any other way to do the refining without boiling the solution?
Sarven Ozdemir
- Buenos Aires, Bs. As., Argentina
2005
Q. To an experienced professional,
I wanted to learn how to easily refine silver from scrap litho film; this has been in my family for generations, my grand father was a silver and gold refiner but he did it in old fashioned way and same goes for my father. Instead of refining gold I became a gold manufacturer at the age of thirteen, and I have been doing this for about twenty-eight years. I have been searching the internet for couple of years to help my dad out so he does not have to go through a long process when he can do it easily. I tried to find a new and advanced way to refine silver and gold but was not successful at it. Please, if anyone can help me out I will really appreciate your aid.
I am not exactly sure about the amount of chemicals he uses but the way my dad refines gold is first he combines silver along with gold and melts it then he throws it in the water which becomes grains, then he puts the stuff in stainless steel or a glass bowl along with the nitric acid. The nitric acid eats up the silver and leaves the gold on the bottom of the bowl, after that my father dumps the liquid in a plastic bowl and washes the gold and then melts which makes it into a 99.99% purity (24 Karat). Now to separate the silver from nitric acid, for this step you have to leave a copper wire in the bowl for 5 to 6 hours that makes leaves the powder on the bottom of the bowl and you throw the water out. Now you melt the powder which makes it into silver. Once again, I will be highly grateful to you if can help me and tell me in simple words, step by step procedure to get 99.9% purity. Thank you.
Tariq Feroze
Gold manufacturer - Iselin, New Jersey
2006
Q. I have just started to venture and little money in Platinum, Palladium or Rhodium gold Dust business, but I'm nowhere related to Gold and chemicals. I have searched the internet and I came to know a lot about Aqua Regia Method and few steps on how to refine gold. But the steps and the vocabulary is too difficult for me to understand. I'm familiar with Acid names. But all I would like to learn is or get a detailed, simple, easy and best procedure to refine Platinum, Palladium or Rhodium Gold Dust. Is there any other way to do the refining to get 99.99% Platinum, Palladium or Rhodium Gold without boiling the solution?
I will be experimenting with a small quantity at home so that I get to know how it is done and practice to get better results. Please experts, I will be highly grateful to you if can help me and tell me in simple words, step by step procedure to get 99.9% purity.
prop - Maharastara, Mumbai, India
2007
Q. I want to inquire how much it will cost to refine gold dust of around 25 kg.
I think I will get my answer soon from this site.
purchasing agent - Delhi, India
2007
Q. Dear Sirs
I have platinum ore but am afraid to process it for fear I will lose possible Rhodium also in the ore. Could you so kindly give some direction on how to process these metals from my little operation at home. Any help greatly appreciated.
Jeweler - San Diego ,California
2007
A. About refining GOLD. I've spent 8 years it it, and I think for a small quantity and only 99.9%. you do it this way:
Decrease% of gold to < or = 25%, as low as possible by copper or silver. Then put in 35%-40% HNO3. Wait 1 or 2 hr, filter solutions with filter paper. Rinse well with D.I water. The black powder is gold. Dry it and melt it and you have 99.9% gold this way without the iron inside the metal.
Anther way to refining gold 99.99% with any alloys: put 600 gram metal in beaker, then put in 3 liters of agua regia (1 HN03 + 3 HCL). Wait 1 day or finish reaction. Filter solution with filter paper. Put UREA slowly into solution until finish boil. Use SO2 gas (compressed gas) put pipe in solution, open the valve slowly. Wait 30 min or 1 hour until all the gold falling the bottom. Solution change to gray or black or blue-gray(precipitating finish). Filter solution and rinse well with water and hot water. Dry and melt. Now you have gold 99.99%. Good luck.
- VIET NAM
June 19, 2009
Ed. note: Thanks very much, Tran. Again, these instructions are for people trained in the same handling of the materials mentioned
A. As we here In Tanzania do, is very simple and accurate procedure. Just take the gold and then use a hammer and a steel doll and hammer the gold till it takes the form of sand particles. Then take a steel pot and pour the gold in it. Then pour some water. When the water comes to the boiling point pour Nitric acid (HNO3) in the pot and let the other particles evaporate from the substance. Then start the same process for the next 2 times. That makes a total of 3 times and what's left shall be 24 kt pure gold. But if done once you shall always get a loss. That is what always happens here in Tanzania and that is why many buyers end up getting losses here. Better stand near the material till the process ends. A blink of your eye shall change everything. People who have come here might understand what I just stated.
Thanks,
- Dar-Es-Salaam, Tanzania
October 31, 2011
Q. Hi, out of 100% gold 9 ct how much gold would I get back. Thank you.
Ana Laystudent - victoria
March 11, 2011
A. Hi, Ana
9 karat gold is 9 parts gold out of 24, and 15 parts of other metals. So if the gold was separated at 100% efficiency, you get back 3/8 (9/24) as much pure gold.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hi,
I have a metal which contains 10% of gold, 10% of silver, 70% of copper and some percentage of zinc and lead in it. Can you tell the process for extracting gold from the metal?
- India
January 10, 2012
Q. Dear Sir,
Can anyone explain if 92% purity gold dust of 1 kg weight of 22 Karat, means 92% pure? How to convert it to 99.999 pure of gold and prepare one Tola (11 gram) gold coins ?
Thanks.
- Dhaka, Bangladesh
March 5, 2012
A. Hi Saeed.
Yes, 22 karat means 22 parts gold out of 24 total parts, or approximately 92 percent gold. Sorry, I can't help you with the rest.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. I dissolve computer processor gold in aqua regia, and I want to know what acid is required to make this dissolved gold into a dust gold?
Ahmad Waqas
recycling - New York
August 5, 2012
Q. Dear sir,
I want to know what's the effect on gold purity if we melt the sample 2 or 3 times?
Will purity increase or decrease when we compare with first result?
Please tell me.
Thanks and regards
Jai Deep
- Delhi, India
December 8, 2012
Q. Hi,
I am running a gold testing center. I purchase gold as per my testing report. But I can't get pure (999) as per report. I lose gold: for 200 grams to 400 gms of old gold at least 1.500 grams to 4 grams for one sitting.
My purification formula is:
300 grams gold (old gold) melting and it's dropped into water (only old gold, not mixed in silver).
It (melting gold) is dropped in box and 400 ml of nitric acid and 1200 ml of HCl. It will do as 1 hour then we keep at for night. Tomorrow morning we will take the gold mixing water and filter the water. The filtering water we mix the chemical water to that (per 100 grams old gold, 1 liter chemical water). Then we wait for 1 hour. then the gold will be down on the bucket. Then we clean the gold and melting.
But first time it will come very well, but nowadays it will not come 999. Please tell me what is the chemical name and how to do it.
OR
Any other type of methods to not lose our gold and take 999 for the old gold.
gold testing center - Andrapradesh, India
December 10, 2012
Q. Please give answer to my question; am waiting for 20 days from my post.
Or any other way to get 999+ pure gold. System is available for it?
I really tried to recover gold like old system but it could not came 999+. It came 99.80% only. This system I explain to you, that is 1st half am doing old gold melting in crucible and make it all old items on %. Then EXP; 100 grams old gold +200 grams of pure silver and melting drop into water to take grains. Then take the grains into stainless steel bowl and add nitric acid and slowly give heat when the brown powder is down.
In bowl then old nitric is dumped in other basket and take new nitric acid add to boil for 30 minutes, then take distilled water and raise the powder with, then heat powder and melt it. But comes only 99.70 to 99.80 only and loss of gold also.
When I test the pure gold it shows Ag id 0.15 and 0.09% Cu and Iridium also.
What can I do for 99.9% gold recovery anybody know please let me know to how it's possible in this method.
gold testing center - Andrapradesh, India
Q. What is happening?! My third request and I cannot get an answer from this site. I want the easy method of gold purification system to get 99.99%.
shiva savant [returning]gold testing center - Andrapradesh, India
May 23, 2013
Hi cousin Shiva. Sorry, I run this free website which is mostly about metal finishing, and help when I can. But when the question is about gold purification, that isn't my area, so unfortunately I can't help. Apologies :-)
But this isn't some weird sort of free consultancy ... it is simply a public forum where readers help each other!
You operate a gold testing center so are certainly very capable of answering some of the questions here, yet you don't :-(
So when you very clearly have the ability to help the many people waiting in line in front of you, but you don't do so, and then demand for the 3rd time that they help you when you won't help them, I think you're being a little bit silly :-( But best of luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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A. Hi Shiva
The big question is why someone from a Gold Testing Centre is asking such an elementary question.
Looking at some of the suggestions in the thread, I would expect the losses to be considerable and the purity suspect.
If any of you are running gold reclamation as a business you should at least have a basic knowledge of chemistry and some lab skills. It is not enough to know how to do the job, it is even more important to know what to do when things go wrong -- and they will!
So, rather than give a direct answer, I suggest that you consult the many text books on extractive metallurgy and gold assaying.
You could make a start at:
www.google.co.uk/search?q=gold+extraction&btnG=Search+Books&tbm=bks
But avoid cyanide and mercury processes unless you fully understand the risks.
Geoff Smith
Hampshire, England
A. Shiva,
First of all, it is quite difficult, if not impossible, to produce 99.99% gold by purely chemical means. To produce that purity, the gold is usually first chemically purified and then run through an electrolytic Wohlwill cell. There are also solvent extraction methods methods that will produce 99.99% purity. It is possible to get 99.95% gold through an aqua regia (AR) process, but you would probably have to process it twice. When inquarting with silver or copper and then leaching with nitric, the results you got, 99.8+% pure, are about as high as you could ever expect. To get higher purity, the brown powder would have to be processed in AR.
Most all karat gold contains silver, which ends up as the main contaminate of purified gold. When you dissolve the karat gold directly in AR, silver chloride (AgCl) is formed. It is fairly soluble in strong AR but precipitates when the AR is diluted with rinse water. This AgCl then contaminates the reduced gold powder. The AgCl can be mostly removed by either chilling with ice and filtering or by diluting and filtering the AR before precipitating the gold. In the latter, add at least 3 times as much water as you have AR. Also, in case any AgCl gets though the system, many refiners leach the filtered and rinsed gold powder with ammonia, preferably hot. This will dissolve any remaining AgCl.
If lead is present, usually from solder, it is also a possible source of contamination. After diluting the AR, as above, add a small amount of sulfuric acid. This will precipitate the lead as lead sulphate and that can be removed along with the AgCl by filtration.
Chris Owen
- Nevada, Missouri, USA
A. Hi Shiva,
Don't be disappointed -- I have an answer to your question.
You use hydrazine hydrate, dilute as 500 ml in 4500 ml water, and use as a gold precipitating chemical.
You are doing Inquartation process which is not being done by you in the proper way. You have to add three times silver of your any karat gold. Dissolve it in nitric acid until all silver dissolves in nitric acid. Here you're doing something wrong. Maybe your silver for inquartation may be less -- so do calculation and do it properly. As per my experience you should get 99.93%
- Mumbai, India
RFQ: I am looking to buy nitric acid and hydrochloric acid to start up some experiments about gold recovery. I searched the net and could not find any. Please let me know if you know where to buy the 2 chemicals. Also, do I need a business license to purchase them?
Thanks.
- Charlotte, North Carolina
January 30, 2013
Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)
A. Hi Maj. As far as I know a consumer would not need a license to purchase things in consumer quantity that are available for sale to consumers like this. For larger quantities, you might need a license or you might simply encounter people unwilling to sell to you. Companies are justly concerned about liability if one of their products is misused, and might only want to sell to licensed industrial facilities. Regardless of laws or licenses, you need to understand how hazardous these materials are.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Okay I am trying to extract gold from computer processors but having trouble in calculating aqua regia. Any help would be really appreciated.
I am using 10 processors as an experiment, so how much HNO3 and HCL should I add (1 to 3 grams gold is expected in it)?
- Karachi ,Pakistan
May 10, 2013
Q. Dear Friends, I am getting the three type of color powders from under ground nearly 30 feet depth, and I think these powders are nearly 2700 years back. It's heavy protected inside of ground; I think this is Gold Dust. The colors are Brown, a type of Green and a type of Red. I have to search on line for Gold Dust colors same-to-same, matched these colors. Also I have to test H2SO4 and sulphate but not getting proper response. Please tell me how to test this powder.
Sri Bangaram- Hyderbad, Andhrapradesh, India
November 4, 2013
RFQ: I want training to learn refining of gold.
bappa paul- beldanga, west bengal
November 12, 2013
Gold recovered from PCB fingers disappeared when nitric acid was added
Q. Trying to find a correct answer to solve a problem a coworker did while we were refining Gold fingers.
He left the bucket in which the acid bath (Hydrogen Peroxide & Muriatic Acid Mix) outside and it rained. He thought the H2O would ruin the Gold for some reason so he said he added roughly 1 gallon of Nitric Acid to 3 gallons of the Acid Mix. When he did this he said it started to produce brown fumes and all of the Gold that was already off and separated from the computer parts just disappeared, turning into liquid & gas form. He pretty much went straight through to it looking like the Aqua Regia process. I could have killed him when I got back from a doc appt.
Can you PLEASE tell us there is a solution for our BIG problem. We would really appreciate your great knowledge and help us out. Great Forum btw, very helpful. Thanks and keep up the good work! We will keep checking your forum every day for your mighty knowledge in helpful answers and tips. Thanks again,
Matt
- New Orleans, Louisiana
August 13, 2014
A. You now have a lot of aqua regia with a little bit of gold dissolved in it, relatively speaking. In order to precipitate the gold with a reducing agent, such as sodium metabisulfite, you must first eliminate the huge amount of nitric acid (an oxidizing agent) that the guy dumped into the solution. Urea won't work. In your particular situation, the most straight forward way is to evaporate the whole thing down to a syrup. Get it quite hot but don't boil or you will loose gold in the vapors. Reduce the heat when the solution level gets low or the solution will splatter. Once this is done, add a little HCl and evaporate again. Repeat 2 more times. Dilute with at least 2 volumes of water. Filter. Precipitate the gold from the clear solution.
Chris Owen- Nevada, Missouri, USA
Need detailed procedure for separating particles of gold from soil
Q. I want to know the detailed procedure for removing gold particles from soil.
Raj Jagdishbhai Gandhi- surat,gujarat, India
November 24, 2014
A. Hi Raj. I don't understand the background behind your question. Please spend more words on your question than you expect people to spend on the answer. Is this a science project question for school? Are you referring to gold panning? You want a detailed procedure for gold panning? Thanks.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Hi mr raj gandhi,
First you have to detect exact % of gold from your soil using XRF or from any lab report. Then only could I suggest a process which is tecno-economically better for you.
- Mumbai, India
Q. My name is ramyar. Please tell me tow powder chemical for recovery gold scrap. Away cyanide, Thank you very much.
fryad fwadqandel - slemany.kurd.iraq
December 28, 2014
? Hi Ramyar. More words please! There are some typos in your question but I can't quite figure it out. Are you looking for how to recover gold from electronic scrap without using any cyanide?
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Hi ramyar,
Please explain about your gold scrap; whether it is jewellery gold scrap or electronic waste (computer IC) scrap?
- Mumbai, India
March 7, 2015
Q. Sir
How to Convert old gold to pure gold? How to Calculate the wastage when converting old gold to pure gold
- SRIKAKULAM, ANDHRA PRADESH, INDIA
March 30, 2015
Q. I refine gold in an easier way by mixing gold in it. I make it in 6 carat gold, then pour into the water. Then I put it on the heat with the HNO3 for 2 hours. I get the pure gold of 99.80, but sometimes it has lead or tin of .20 percent. So how can I clean that lead or tin in this process? Please answer, I need it urgently.
devakar aggarwaljob - Delhi, India
May 31, 2015
A. Dear devakar,
You are following inquartation; if your metal contains tin or lead go by aqua regia process. You will get better purity.
Does your scrap metal contain lead or tin, please check?
bhupesh mulik
cac admixtures - Mumbai, India
Pure gold grain is wrong color
Q. I have made grain thousands of times from scrap. However this grain has come out much darker in colour. It still tests by XRF and assay as 99.96. How to change the colour?
Nathan Rivers- United Kingdom
July 2, 2015
A. Nathan,
Put a little grain in a little hot 10% sulfuric acid for about 5 minutes, rinse it, dry it, and compare the colors. If it lightens up, the dark color on the surface is most likely due to base metal oxides. If base metals are on the surface, they are also in the metal. This would mean that the 99.96% XRF reading is most likely in error, which wouldn't surprise me at all. At that high a gold reading, I have zero faith in XRF. If the purity were actually, say, 99.5% or maybe even 99.9%, there could be enough base metal contamination to cause some surface discoloration. It doesn't take much.
If the 10% sulfuric doesn't lighten it, try a little warm 15% nitric or 40% HCl and see what that does. If nothing lightens it, the color is probably throughout the metal and this would mean the gold purity is quite a bit lower than you think it is.
You might also abrade or scrape the surface and look for a color change.
It is often difficult to see the true color of shiny metals. Place a Kleenex or other tissue over both this shot and the shot whose color you're comparing it with. Put a drop or two of water on each one. Try to gently smooth out the wrinkles without tearing the Kleenex, so it conforms to the shot. Now you should be able to see the true colors. We used this test to compare the plating colors of various formulations of "color" gold plating solutions.
What do you mean by "assay" - fire assay?
Was the shotting water clean?
- Nevada, Missouri, USA
A. Dear nathan,
While you are making grains, you pour a metal in clockwise direction and rotation of water in which you are pouring melted metal should be anti-clockwise. see the results about colour, and time to refine pure gold.
When you test the grain by XRF, it has a limitation which gives purity of coating surface. Better to do fire assay.
cac admixtures - Mumbai, India
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