# Making Gold Chloride



## emanphoto

In a somewhat reverse need than what is typical on this forum, I thought I'd check to see if there is a tutorial for making gold chloride as this is what I'll need in the end. In watching your youtube videos I saw that purity standards seems to be pretty high and your lab procedures good esp. in pointing out that one should NOT make the aqua regia alone but add each acid individually to the flask. I never knew that! I've searched the site here to see if there is an article or pdf on this process first with no luck. I've also seen this video which seems incomplete for my purposes but gets close. http://youtu.be/FS7tsBj0Q5A For instance, in this video he doesn't completely dissolve the gold and doesn't say why. He's left with a gold chloride solution but how to calculate the percentage if he's removed the gold from the process?

FYI's and background
So here is what I do. I work with historical photographic processes using at times, gold chloride, palladium chloride, potasssium chloroplatinite, and uranium nitrate to tone prints or to act as the actual photographic emulsion for making prints. Uranium nitrate can be mixed with distilled water and applied to paper, dried and then a large negative is placed in contact with the coated paper and exposed to UV or sunlight to expose the print. After exposure the print is processed in potassium ferricyanide solution revealing the image. Gold, platinum, and palladium can also be used in combination with light sensitive ingredients to make their own emulsions, but typically I use gold only for toning prints. I used to have a lab specializing in analog printing and here's the page of these historical processes I offered. I've kept the old site up on a free host for reference. http://archival.comli.com/Historical_Processes/historical_processes.html

With that preface, photographic needs are somewhat simpler in that food grade chemistry is typically OK for our uses. For metal compounds higher purity is preferred as we're usually paying for these and this lowers the chances of having unpredictable results in these already somewhat unpredictable processes. Unpredictability in the printing process can come from humidity variations, paper composition, etc etc etc. So having a good quality metal compound is preferred.

I've made gold chloride twice many years ago done by dissolving a Krugerrand in aqua regia using a double boiler setup on a camping stove outdoors and once using a 1 gram lump of souvenir gold from some tourist spot that I was given. I hammered the krugerrand flat before the process. Being this was a long time ago, I don't remember all the steps I did plus I needed the help of a chemist at DF Goldsmith to help me to figure out the percentage of my solution as this is really important for my use. Math is definitely NOT my strong suit. I've read in historical literature that gold coins were used by photographers to make gold chloride.

So what I'm hoping for is a tutorial on how to make gold chloride with instructions on how to calculate the percentage of the solution from the quantity of gold used, or however is easiest to calculate this. I now live in Bangkok so 24K gold is pretty easy to come by, if you have the cash of course! They sell gold chain by the link here. Obtaining the acids shouldn't be too difficult. 

Thanks for any help.

Eric


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## butcher

Eric,
If you just want to make gold chloride with pure gold it can be easy, but to recover gold, or refine it you will need to do a lot of study.

I would burn any oils off the gold, you will need clean glassware designed to be heated.

Gold will dissolve in a solution of (HCl) hydrochloric acid, and (HNO3) nitric acid called aqua regia solution, for each gram of gold you will need about 3.8 ml of 32% HCl, and about 0.95ml of 70% HNO3.

This will make gold chloride solution.

It is best not to use too much HNO3, (because it would make reducing the gold back to metal later difficult as the free nitric will redissolve the gold as you are trying to reduce it back to a metal chemically.

So by covering your pure gold in the HCl (calculated) and adding the nitric in small additions (from your calculated amount nitric you may need) we can dissolve the gold without excess of nitric acid, heating the solution will also help to complete the reaction (do not boil), to insure all the nitric has reacted you can complete your solution without dissolving all of the gold, basically letting the heated solution react until the remaining gold will no longer react with the acid solution, to use up any free nitric in solution.

The gases formed are extremely corrosive and dangerous and can be deadly to breath, this should be done in fume hood or outside where you can keep from breathing these fumes.


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## samuel-a

Are you in need for gold chloride AuCl3 or chloroauric acid HAuCl4?
The later is produced via AR treatmet of pure gold.
Gold cloride can be produced by passing Cl2 gas over heated (150C+ IIRC) gold powder in qartz test tube.
AuCl3 could be collected with distilled water and later evaporated to crystalization.


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## emanphoto

Sorry for my late reply here as there was an issue reaching the site and I had to use a VPN. Also I couldn't find my post so I was kinda lost and had to write the admins to get back in.
In any case thanks for the good info. I need to end up with a 1% solution of gold chloride. The 1gm ampules of solid gold chloride one used to be able to buy years ago were exactly what I needed and have used, but I have no idea how they were made. 
Nowadays living in BKK having a compound shipped from my former suppliers in the US such as Bostick & Sullivan, http://www.bostick-sullivan.com, etc, is too expensive and risky as far as getting thru customs.
My lab, compared to most members here, is fairly rudimentary so the chlorine gas method is not an option although I remember reading about that years ago. I have the simplest of lab gear to use in the preparations of my photographic solutions, a beaker or 2, pipettes, graduated cylinders, and the like. 

What I remember doing years back when I made gold chloride was I made aqua regia, I don't remember the ratio or quantity used, but had been told that once the reaction slows or stops, the keep adding HCl to the gold. It eventually dissolved but being the very deliquescent compound that it is, it's pretty much impossible to accurately weigh it so that's basically my question. Once dissolved and the acid has evaporated, what is the mathematical formula for figuring out how much gold chloride I've made assuming I start w/a gram of 24K gold. I know people here are usually trying to achieve the opposite results and end up with gold, but I figured this is a good place to start asking.  

Re: gold chloride AuCl3 or chloroauric acid HAuCl4 I don't know. I recall them being the same but I guess not! I'll have to ask some folks and report back.


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## butcher

I can be wrong.

Personally I do not see too much difference in Auric Chloride AuCl3 (Au2Cl6) or (2AuCl3), and Chloroauric acid HAuCl4 (AuCL4H3O), besides the excess acid, HAuCl3 is what we make in Aqua Regia and is highly acidic, AuCl3 is what we get when we lower the acidity with evaporation or when we use up all of the acid heating it strongly to dissolve more gold consuming excess acid in the reaction.
It is both gold dissolved and made into chloride salts of gold, both can be made in aqua regia, or one of the other methods we use to form the chloride salts of gold, I believe the acidity of the solution or salts is where the difference in these gold salts differ from each other.

If we knew how much gold you dissolved into a small volume of aqua regia solution and diluted it with a certain amount of water you would know how much gold per liter you had.

If we had a salt of HAuCl4 not counting moisture or liquid, we would have about 55% gold in the evaporated acidic gold salt.
If we had a salt of AuCl3 not counting moisture or water, we would have about 65% gold in the evaporated gold salt. 
This is figured using the molecular weights of gold, Hydrogen, and chlorine


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## goldsilverpro

emanphoto said:


> Sorry for my late reply here as there was an issue reaching the site and I had to use a VPN. Also I couldn't find my post so I was kinda lost and had to write the admins to get back in.
> In any case thanks for the good info. I need to end up with a 1% solution of gold chloride. The 1gm ampules of solid gold chloride one used to be able to buy years ago were exactly what I needed and have used, but I have no idea how they were made.
> Nowadays living in BKK having a compound shipped from my former suppliers in the US such as Bostick & Sullivan, http://www.bostick-sullivan.com, etc, is too expensive and risky as far as getting thru customs.
> My lab, compared to most members here, is fairly rudimentary so the chlorine gas method is not an option although I remember reading about that years ago. I have the simplest of lab gear to use in the preparations of my photographic solutions, a beaker or 2, pipettes, graduated cylinders, and the like.
> 
> What I remember doing years back when I made gold chloride was I made aqua regia, I don't remember the ratio or quantity used, but had been told that once the reaction slows or stops, the keep adding HCl to the gold. It eventually dissolved but being the very deliquescent compound that it is, it's pretty much impossible to accurately weigh it so that's basically my question. Once dissolved and the acid has evaporated, what is the mathematical formula for figuring out how much gold chloride I've made assuming I start w/a gram of 24K gold. I know people here are usually trying to achieve the opposite results and end up with gold, but I figured this is a good place to start asking.
> 
> Re: gold chloride AuCl3 or chloroauric acid HAuCl4 I don't know. I recall them being the same but I guess not! I'll have to ask some folks and report back.



They are different but there are some indications on the internet that either would possibly work for gold toning. It seems that the big chemical companies, such as SigmaAldrich, sell the AuCl3 as crystals and the HAuCl4 as a 1% solution. HAuCl4 solutions are linked at the bottom of this page.
http://www.sigmaaldrich.com/catalog/product/aldrich/334049?lang=en&region=US

Making AuCl3 is more complicated than making HAuCl4. Another way you could write HAuCl4 is AuCl3.HCl, AuCl3 with an HCl molecule attached. I've never made AuCl3 but, according to the internet, the common way is with hot Cl2 as described by Sam above. Another way mentioned in the literature:

Dissolve very pure gold in aqua regia. ; 
Evaporate to a syrup several times with additions of HCl to eliminate nitrates. This results in an acidified HAuCl4 solution; 
Evaporate, without exceeding 120C (if you do, gold metal will result), to yellow HAuCl4 crystals. This can be done a hot water bath; 
Heat the yellow crystals at 200C, or a little less, to drive off the HCl molecule, resulting in red AuCl3 crystals.
In this process, evidently, some insoluble AuCl will be produced along with the AuCl3. This is filtered out after dissolving the red crystals in water.

Were it me, I would buy the AuCl3.


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## Lou

As mentioned, it can be made by recrystallization from a suitable ether (THF, dioxane, Et2O).

If you're only needing a small bit, best to pay the premium.

Lou


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## rickbb

How would you discover/calculate the percentage of gold in a given volume of gold chloride if you did not know your starting value of gold? Is there a simple method or would you need a titration setup?

As in digesting foils from e-scrap in the HCL/CL method. I wonder about this every time I do a batch of foils.


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## butcher

I would take a measured sample and precipitate the gold, figure it from there.
Having the equipment to measure accurately would be a problem.


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## emanphoto

I knew how much Au I started with, but I'm pretty sure 1 gm of Au doesn't ≠ 1 gm of gold chloride. I'm looking for any tips RE: the process and a formula for calculating a given quantity of gold's weight once processed into gold chloride. The one step I've seen mentioned in this discussion that I didn't do was the addition and evaporation of distilled water after the aqua regia treatment which is a good tip! Thanks goldsilverpro. The solution is yellow if that helps identify which one. So to start, let's say I'm starting with 1 gram of gold. From there I can extrapolate for any other quantity of 2,3,4 grams etc.

The Sigma-Aldrich price from the posted link is $139 USD for 500_mg_ from their Singapore site (http://www.sigmaaldrich.com/catalog/product/aldrich/334049?lang=en&region=TH), and my former supplier charges $42 for 100mls of their "1% Gold Chloride Solution - 100 ml 
Hydrogen Tetrachloroaurate (III) Trihydrate." The the S-A compound is described as "Violet to Maroon or Brown" which is not like any gold chloride I've used. When I've had the actual crystals, they were a bright yellow. My crystals that I made years back were a greenish yellow IIRC and was probably not made as well as I could have with the resources now available thru the internet. 

The problem is I live in Thailand and shipping here is extremely expensive and not without risks getting through customs and the postal service in general. I've read of a person's vitamin shipment from the US being waylaid requiring a personal visit to the customs office after a call from a connected friend and "fees" needing to be paid before they released the shipment. I don't need the hassle. Since the price of 1gm of gold is $38-ish, and I'm guessing that one gets more gold chloride than a gram using the aqua regia process, it then it makes sense to make it myself to save money and also skip the hassle, cost, and uncertainties of shipping here.

Back in the 1850's and onward some photographers used gold coins to make their gold chloride and the assay of those coins, not being pure gold led some photo historians to believe that those impurities gave the prints the gold chloride was used to tone their look. Since the gold chloride I use is for toning and not making the emulsion, that level of purity is fine whereas palladium chloride and Potassium Chloroplatinite is used for making emulsions and a higher purity is desired. For most of my chemistry, food grade/photo grade is fine. This leads to the occasional rock or dead bug in your EDTA or sodium sulfite or what have you which is easily filtered from your solution. That's OK. The assay of a 24K gold link or coin may not be 100% pure gold, but in this case that's OK. I don't need to make a reagent grade but I don't want to make sloppy or dumb mistakes which, believe me, I can do not being a chemist.  
In the realm of chemistry I think of myself as a cook and not a chef, i.e. I can follow instructions and make something, follow mathematical formulas to calculate what I've made, but I don't have any real comprehension of the processes, (unless explained) going on when I mix things together.


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## butcher

These are just my ideas and suggestions, which may or may not help.

Gold crystals
Gold Chloride Hydrate 
(Chloroauric Acid / hydrogen tetrachloroaurate)
H(AuCl4)·H2O 
(depending on acid or water content of the crystals made)
Gold content 49% to (55% is what I calculate with no water of crystallization involved).


A 1% solution would be 10 grams/liter
by weight.

Now I am unsure if you are wanting 10g of gold in solution, or 10g of gold chloride in solution.
but from this you can figure either from the facts above.

You could buy 999 gold and make your own solution (or crystals, which would be more difficult), I would not use coin, or karat gold, unless you refined the gold first, not only because of base metals or silver, but because of the difficulty involved ...


I do not know how critical the exact mix or % you need.
You could file off (use clean file) and weigh the amount of 999 gold you need, incinerate the gold filings but do not melt it to burn off oils, into a clean beaker add the gold filings and cover with 32%HCl (use 3.8 ml HCl/gram gold).

In a separate test tube add 70% HNO3 (0.95ml/gram of gold).
Heat the beaker with gold and HCl. This can be done in fume hood or outside, on a solid burner hot plate,you can sit the beaker in a Corning ware porcelain dish (Corning Pyroceram), as a catch basin, sitting on the hot plate.
With a pipette slowly add drops of HNO3, wait for gold to dissolve, when small bubbles or action of the nitric cease add another drop and wait, the trick here is to use no more of (calculated amount) HNO3 than needed, to get the gold filing dissolved, before the last bit of gold is dissolved, stop adding nitric acid, continue to heat (we just want gas fumes leaving solution we do not want to boil the solution), to evaporate off some of the acids, after concentrating the solution (from yellow to an orange/RED color), if you need a drop of nitric to finish dissolving the gold filings you can add it.

Now I would continue to heat the solution (vaporizing off any excess H2O, HNO3, and HCl), keeping solution hot (so crystals do not form yet), getting the solution a thick red orange syrup, add a few drops of HCl (if you see a red cloud of smoke (NOx), you still have free nitric, continue to heat to evaporate free acids, to concentrate again, again repeat the drops of HCl (watching for the red cloud), evaporate for the third time to drive off free acids. 
this will give you a concentrated gold chloride solution, if you do not evaporate to crystals it will contain some excess HCl, If this would not hurt your work I do not know if I would go to the trouble to crystallize the gold solution, which could be done with slow evaporation and keeping it acidic (and with Lou's suggestions).
If you can use the concentrated gold chloride solution, it would be easier than trying to crystalize out the gold where you risk decomposition of the Chloroauric Acid. 

.


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## blackwolf365

seems like it would be easier to just buy gold chloride in solid form, like table salt for example, in the needed amounts. if this is actualy so, where does one go to buy, say, a 50 pound bag of gold chloride? and would this company have other metals in chloride form? like silver for example.


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## g_axelsson

Sure, you can buy it. https://saltlakemetals.com/product/gold-chloride/

Looking a their inventory it seems like they have other silver salts but not in chloride form. It's easy to make though.

Göran


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## blackwolf365

what about gold chloride in a solid state, like youd find sand or sidewalk salt in. something that can be used to mix your own solutions with.


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## galenrog

Please follow the link to Salt Lake Metals provided by g_axelsson. Come back and convince me to use gold chloride crystals or powder over gold chloride solution.

Time for more coffee. After my nap.


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## blackwolf365

was not trying to convince anyone of anything and will not try to now. just looking for information for my own use.


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## g_axelsson

Sure, you can buy it as a powder too.

https://www.sigmaaldrich.com/catalog/product/aldrich/481130?lang=en

Just the first hit I got on google.

Göran


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## blackwolf365

did some more research. methinks the liquid form might be easier to deal with as the strait pure solid form would absorb water from the surrounding air and dissolve rather quickly. this might cause issue with storage so, nah.


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## galenrog

Dissolving is not the problem. The problem is the powder or crystals quickly becoming a sticky, nasty, messy paste. Gold chloride powders and crystals have their place in industry, but those applications are limited, and are typically well outside what anyone involved in recovery or refining of precious metals would need.

Time for more coffee.


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## blackwolf365

for my personal intentions, liquid form would be more effective and convenient. though i may at some point make up a large quantity of it in dry form just for the hell of it. maybe use it to wow a few kids by letting them watch it liquefy right in front of them in hopes it would trigger an interest in science.


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