# boilng point of HAucl4 [missing gold]



## masarh (Jul 5, 2010)

hello 
i have this situation that i'm missing some gold  when i'm refining with AR
in interenet i have found that boilind point of HAuCl4 is 100°C (212°F) [http://www.saltlakemetals.com/MSDS_Gold_Chloride.htm] 
could it be due to boiling of AR for a long period?


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## g_axelsson (Jul 5, 2010)

That's not correct. The boiling point for HAuCl4 is much higher than that. The MSDS sheet is for 1% solution and that is the boiling point of the water, not the gold chloride.

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

If you are boiling hard some gold may be transported out via steam and small droplets. Sorry I can't help you more than that.

Btw, how big are your losses and how do you know you are losing gold?

/Göran


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## philddreamer (Jul 5, 2010)

Hi masarh!

Not necessarly bacause of boiling for a long period masarh, but more likely for not covering the solution.
You will lose some gold from AR thru evaporation. I have experieced that.
You should cover the solution to prevent vapors from going to thin air, or, on the side of the walls. :roll: I'll be recovering some by wiping it with some HCI-CI & fiber glass. 
One way I've been able to cut from losing some of my gold is by using a watch glass to cover my beaker. Vapors condense on glass & drip back into the solution. Also, "bring to a boil". I get rid of the nitric in the AR by boiling, not urea. So, I boil, long enough, to the point that the solution starts to behave like syrup. This takes a while. Lower the heat @ this point. You watch the bubbles, they look thicker & stay on top longer before popping. Then add a slpash of HCI & "wet " the solution again. Do this 3 times. Then add three times the volume with tap water. Any AG will show as CI; let sit & filter. This will get rid of nitric & you should drop gold with SMB without problem. 
But yes, you will lose gold thru evaporation. Also, every time the bubbles burst & spray out. 

Phil


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## butcher (Jul 9, 2010)

phildreamer good post, 
my suggestion lower the temperature, evaporation does not need to boil, It is usually called boiling off nitric but slow evaporation would be a better term , below boiling, it takes about the same amount of time, nitric acid in solution, such as aqua regia, when water is in solution it will evaporate before the nitric acid, as the nitric in solution concentrates up to its azeotrope, once it is about 68% nitric, the 68% will start to boil (bubble gasses of NOx) at this point if temperature is high the solution can foam over, lowering the temperature can keep this violent reaction down and keep the valuble metals in your pot, the watch glass is a good Idea.


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## philddreamer (Jul 10, 2010)

Thank you butcher, I'm learning from the best!  
I've been busy working on my 3rd oz. while put'n up a small shed with all the gadgets. 

Phil


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## chemist (Jul 10, 2010)

You can avoid the need to use heat to remove the excess nitric by limiting your nitric additions. If you don't put in an excess of nitric, then you won't have to get rid of it. You save money, energy and time.


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## lazersteve (Jul 10, 2010)

chemist said:


> You can avoid the need to use heat to remove the excess nitric by limiting your nitric additions. If you don't put in an excess of nitric, then you won't have to get rid of it. You save money, energy and time.



This is a key discipline to learn for all refiners. Any excess reagents you use are simply wasted money and more headaches in the end once you have to precipitate and dispose of the waste.

Waste not, want not.

Steve


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## butcher (Jul 10, 2010)

noticed the violet stains out of the pot in picture above, theres $$ splashing out, as Steve stated using only reagents needed is something we all need to learn, why would we want to waste our nitric by evaporation, when we could use it to refine with, useing to much nitric is also money splashing out of our hard to get nitric bottle. 

New refiner's will get there best material, be so exited to learn refining, not study enough, getting only a portion of the knowledge of a process, or several processes mixed up in their head, add a extreme excess of chemicals to a lot of valuble metals, mixed with base metals, make a big mess, then ask for HELP to recover the lost gold and how to deal with this mess,
after then they may be ready to slow down and read Hokes.

Philddreamer how about adding an old fiberglass cafeteria tray under your hot plate, they work wonders. I am impressed at how fast you have learned here on the forum and love watching you turn out those beutiful gold buttons. dreaming big must work.


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## philddreamer (Jul 10, 2010)

Butcher said:
"Philddreamer how about adding an old fiberglass cafeteria tray under your hot plate, they work wonders. I am impressed at how fast you have learned here on the forum and love watching you turn out those beutiful gold buttons. dreaming big must work."

Indeed Sir! I'll put one of them trays very soon. I've been selling the gold as I refine it & buy tools of the trade, & more gold, ofcourse.  I'm also working on a small shed.
I start thank you for taking me under your wing when I first became a member of this great forum. You were very patient explaning the "why" you must do this or not do that. Same with the other experts & fellow members, taking time to answer my Q's. And I guess I'm a pretty good disciple. :roll: 
And speaking of gold buttons... this is 24gm. For a total of 2.52 oz so far.
I'm half way to my 5 onces!!! 

P.S. The photo above was to show that yes, you can lose values. I was in the process of clean'n it. I recovered a bit over a gram. Since I bought the watch glass, & started using less heat, I cut the loses by 95% or better. We live & learn!


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## Barren Realms 007 (Jul 10, 2010)

Thats is looking real nice. 8) 

I need to get one of those setups for the map gas tourch to the propane bottle.


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## slouma37 (Nov 13, 2010)

Ohhhhh my God !
I lost like 1000 $ (+- 700 €) since last month just coz of this . Last night i saw like easy 1 cm³ of gold powder in my pyrex beacher and then after boiling for 5 min , i realised that i lost like 3/5 or 4/5 of it and ended with 0.2 Gr instead of normally 1 Gr expected.

I accused the use of urea before...but it's in no case the cause of loss...
An exprience i did last night of redissolving and recovering 1 gr of gold powder, i realised that i can get 0.98 Gr of powder dried ,if washed with HCl without heating. I ended heating to reach like just 50°C for this wash, not more, and that worked great.

So i swear to never boil a gold solution without a cover ...NEVER EVER BOIL A GOLD SOLUTION WITHOUT A COVER THAT FIT PERFECTLY TO THE HEATED BEACHER.

now i hope , i dream , i dream big like phildreamer advised and hope i'll start from now on recovering respectable amounts of GOLD otherways my wife will ask for the divorce.
all the best...


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## HAuCl4 (Nov 13, 2010)

I never boil because I'm a cool guy. 8) 

Some ladies think I'm hot, but really I'm cool with that too. 8)


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## slouma37 (Nov 13, 2010)

WTF @ HAuCl4 ? u not cool man, u cost me 1000$ (f that) LOL
i read that u can even boil at 30°C and i cant find a complete text on u ... :mrgreen:


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## butcher (Nov 13, 2010)

A lot of us are used to saying boil when we actually mean a slower evaporation, no large bubbles popping, these popping bubbles carry metals and values, when we actually mean to just evaporate at a lower temperature, where fume's escape but not metals being carried off. (Watch glass is very good can also help to indicate if we have metals in those vapors).

in steam boilers we call that foaming or carryover, if total dissolved solids too high, or the chemistry is out of whack, or oil on water surface, the boiler will foam, or we get a surface tension(scum or oil and so on) the bubbles will grow very large and when they do pop they will carry over contaminants into the steam and also carry more water or actually slug large volumes of water out of boiler into the header steam line (which can create some dangerous situations (water hammer busting steam lines).

When we are evaporating our solution and get it more concentrated if we "BOIL" I believe we can "carryover"our gold out of the pot.

Anybody seen any of those lepricons lately, I want to follow one to that pot of gold.

It is a bad habit for us to use the term Boil when actually meaning to evaporate.

Sometimes bad habits are hard to break, and if we avoid them to begin with we will be better off in the long run. 

Let’s try to stop saying boil when we mean evaporate.

Phil on your Inquartation notes you made up, it say's boil, can you edit it to say slow evaporation?


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## slouma37 (Nov 13, 2010)

Thanks butcher,
i'll always evaporate and never make any gold solution goes to boil.
have anyone a good documentation on the AuCl4- or HAuCl4 ?
coz what i learned is that it can exist on both states Gaz and solid even at 30°C :shock: that mean if we do any refining in summer we can lose a lot of gold, or even when evaporating w'll get some loss just coz of this dual state of this molecule. it's really confusing...


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## butcher (Nov 13, 2010)

I do not have that information, the HAuCl4, is just more acidic than AuCl4, 30 degrees C is about 86 degrees F, pure HCL is a gas and boils at about minus eighty five degrees C, and the HCl acid Hydrochloric acid (HCl gas and water) boils about 48 deg. C or 118 degrees F and this solution 38%, but also consider here the term BOIL, is being used for a change of state (like a liquid to gas) and may be in reality meaning evaporation and not an actual rolling Boil, 

These terms can get confusing. Especially when we are just saying does not use the word boil but evaporation and in science they may use the word boil?

I do not think you will loose gold from solution by atmospheric temperature even living in our hottest desert. Now I do believe your solution will concentrate removing some water and more volatile liquids.

another thing is a solution can have different "boiling points" for different concentrations (do some research on azeotropic mixtures), these azeotropes can change boiling points with different concentrations of acid and water, also having more than one acid or a metals in solution can also change the azetropic boiling points, stay in solution and become salts of metals than to leave as vapors if we provide the right conditions,

Sorry I am not much help here maybe someone with more of an understanding of chemistry will chime in to this conversation and help you and straighten me out if I am mistaken.


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## slouma37 (Nov 13, 2010)

"I do not have that information, the HAuCl4, is just more acidic than AuCl4" No the HAuCl4 is just the acid form of the ionic AuCl4- .
We generally speak of boiling POINT of a chemical compound in chemistry and it's just the maximum temperature that this compound can reach in liquid state before it evaporates under some pressure...that's all of it.

So if we start heating something , imagine it like just some very little amount of molecules let's say water reach fastly 100°C and start's to change their state from liquid to vapour, then while heating more and more water molecules reache the 100° and starts them self to change state coz with more heat molecules enter more and more in collision and then heat faster and evaporate faster.

To simplify Let's consider the word BOILING just as the visible phenomenon, the visible bubbels we watch on the surface of the solution and the part that is invisible also and bubbles coming from the down side of the solution. 

And infact of course some gold particles in this case will goes of the solution and their amound or % depend on their boiling point. (thus why the gentil heat avoid this loss of gold.

but why the hell i know this and i still act like a dumb ? coz instinctively i cant figure how the heavy atom of gold can escape out with vapour. it's like refusing to admit the evaporation of mercury as in liquid state is soo heavy but evaporates so fast with temperature.
i know kinda all chemistry laws and principes and i still act like a deleted. *Clean up your language*. Harold.

"I do not think you will loose gold from solution by atmospheric temperature even living in our hottest desert"
A : if the boiling point of HAuCl4 is 30°C than w'll loose alot of gold when refining that's why i want some document to confirm the boiling point of HAuCl4. and even the chemical propreties of AuCl3 and AuCl.

voila


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## butcher (Nov 13, 2010)

where did you get the boiling point you stated as 30 degrees centigrade?
to me by itself this number means nothing.
what are the conditions of the solution? 
how much water, how much nitric acid, how much HCl, how much gold or other metals are in solution, density? all of these factors will have a bearing on the boiling point. or the point at which a volitile substance like (mostly) water vapors off, then mostly nitric acid vapors off, then HCl vapors escape from solution and the gold concentrates as density gets higher, during this time the azeotrope for each of these are changing as well as their boiling points (azeotropes).

so we cannot say HAuCl4 has a boiling point of Bla-Bla-Bla
without also stating some important facts such as density, and possibly the state of our solution.
we can say if it was a 2% HAuCl4 solution it would have a boiling point of 100degrees centrigrade or a slight bit higher, because it is mostly water, and would boil at waters boiling point approximatly, and as the solution evaporated , the boiling point will change, as volitile gasses leave solution, depending on their boiling points or azeotrpic boiling points or solutions boiling point will also change.

I have only begun to learn chemistry and never been to school on it, just learning what I can, and yes I am a hilbilly but untill you can show me where I am wrong on this I will stick to what I have gathered from reliable sources concerning this matter.


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## slouma37 (Nov 14, 2010)

Sorry butcher it's the Fusion point i gave not boiling point. The fusion temperature of HAuCl4 is 30°C means that at 30°C.
The boiling point is 200°C in French wiki http://fr.wikipedia.org/wiki/Acide_chloraurique

But the information given in the english wiki is diffrent : http://en.wikipedia.org/wiki/Chloroauric_acid here they gave the melting point and it's 254°C.

Now what do we have in our standard solutions of gold that have been precipitated and syhoned, ready to be washed with HCl ?
we have: HAuCl4, very little H2O , very little HCl and let's say some of unwanted molecules such as : Urea Nitrate or just urea, and some other metals in traces.

Let's focus just on theese molecules / ions, considering the denoxing was perfectly done, we dont need to speak about azeotrope and so on...

So What we just want by washing is :
* to get rid of the reste of unwanted traces if other metals precitpitated with our gold or those who dident react previously.
* get rid of the urea excess or urea nitrates (that dident react to give gases :
(NH2)2 CO [urea] + HNO3 [nitric acid] ------> 3 NO + CO2 + H2O )
* AND MOST OF ALL now we want our pure gold chlorides molecules only to stay :
Au2Cl6 + HCl <---------> HAuCl4
in this last reaction we do have to care about all it's chemistry caracteristics
boiling point, fusion point, only this coz we consider our initial solution of AR was clean, the most clean we can.
Why i port my interest to this reaction is coz it's a complex reaction in reality
it depends on pH and Temperature (not pressure coz i consider working under atmospheric condition) and (may some gold is under AuCl form ? ) 
i want to try to explein this reaction in details if no one else have done this before, or knows how things goes considering this 2 parameters pH and Temperature.

Hope u understand me


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## butcher (Nov 14, 2010)

slouma37, good post, and yes would love to learn, thats why we are here.

note the boiling point in those wiki articles also say (decomposition), I assume from the state they are in now. if you know different help me out.

I would stay away from using urea, I find it just complicates matters (just my opinion).

excuse me if I understood your posts above about boiling away thousands of dollars of gold from your solutions, you should not lose gold if processed properly, you can missplace some for awhile, but actual losses should almost be insignificant.

if gold chloride boiled away as easily as I felt you were saying we would just be vaporizing off our gold not refining it with the processes we use. surely I was missunderstanding what you were saying?

good conversation slouma37, I agree with most of what you are saying, but where I don't, I will need some reference material, to show me, I am slow to learn but once I start I have to dig up all the facts till their are no more to find on that subject, and I usually do not take one reference as proof. you can tell me its hot but untill I burn my hand I will not know it is hot.

slouma37, lets help each other learn, I would like you to explain the reaction. thanks.
Richard Butcher


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## slouma37 (Nov 14, 2010)

Hi Richard,
if u noticed, i try to focus the maximum on the gold reactions and today i learned that all gold chlorides : AuCl, AuCl4-, HAuCl4, AuCl3 and Au4Cl8 are also subject to light dissociation. Yes the simple day light can let the gold goes out , evaporates (of course specially) if the beacher is not COVERED.

It's a bit comprehensive as the Cl2 molecule is subject to dissociation when exposed to light.

Let's say w'll work from now on on a candel light by night...to resolve this problem definitly. and secondly COVER always any gold chloride solution to avoid any evaporation.

Now about Urea, i was incriminating urea for a while to be the most step ruining me...after some essay's i noticed that i can recover 98% of my dissolved buttons recovered with the use of urea to neutralyse the NOx's AND any excess of HNO3. why the HNO3 ? i insist on this coz steve says somewhere that Urea only react to eliminate's the NOx's and not the HNO3. It's false. (forgive me Steve if it was not u who said that)...
Coz Urea reacts with HNO3 like this:
5 (NH2)2CO + 6 HNO3 ---------> 8 N2 + 5 CO2 + 13 H2O
and also can react this way giving urea nitrate in solution :
(NH2)2CO + HNO3 ------------> CO(NH2)2.HNO3 

So Urea swing both ways...

and why it's my favorite way of denoxing , it's coz it reduce the TIME of denoxing especially when we used an excess of HNO3, in the case we don't know the exact mass of gold we expect. + The reason of we cant denox with heat without letting the solution UNCOVERD. 

Ok here i follow the advices to put cristal urea in hot water before adding it little by little in my AR to denox tille it stops fizzing definitly.

hope all this helps


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## butcher (Nov 14, 2010)

I really do not think the light vaporizes gold, but bielieve that it can change the gold salts state, like HAuCl4 to AuCl4, not loosing any gold just loosing hydrogen.
again this is just the way I understand it, and I am just learning also.
and if any gold actually did evaporate my guess it would be hard to measure the weight difference without scientific atomic scales, again my speculation.

using urea is up to you, but here is an Idea that works for many members here, only use the nitric to get the job done, that way you will have none to very minute excess nitric to eliminate, also another trick is adding gold button to use up any excess nitric in solution. I am not saying the urea will not work, I just believe their are better way's, but each of use may choose to recover and refine our gold differently, that does not make either of us right wrong or left.
but if it is high quality gold you seek then I would read some of the older posts of Harold, and GSP on eliminating the nitric from aqua regia, between these two professional refiners I think we can learn the best of two worlds, and gain from almost a century ogf their combined expierience.


slouma37, my friend, please spend some time reading the posts on this forum, their are some professional refiners that can teach us more than we dreammed of learning


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## philddreamer (Nov 20, 2010)

Butcher wrote:
"Phil, on your Inquartation notes you made up, it say's boil, can you edit it to say slow evaporation?"

I fixed it. Thanks!

Phil


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