Precipitating gold from AR with SMB

[Ruan]

Hi I'm fairly new to gold refining. I'm concerned about a brown fizzing when i add the SMB to the AR. Could this be a result of too much nitric acid in the AR solution? I have tried to add urea to neutralize it but the brown fizz is still there when i add SMB. If anyone can give me any advise on this, i will be so greatfull.
I have a lot of other questions too to better my technique.

Kind regards
Ruan

 

[niteliteone]

Where are the details of what process you used to get to this point ???

ie... type of material ???
amount of material supposedly in solution ???
if you followed set procedures to remove ALL base metals before starting a refining process
Amount of each chemical added to get to where you realized you don't have a clue what you are doing.

Have you thoroughly read Hoke's book dealing with what you are trying to do ???

Start there and figure what you have done wrong. When You can explain that, then you are ready to understand what we might tell you on fixing your mess.

 

[rickbb]

When you add urea did you do so until the fizzing stopped with one or two balls of urea floating around?
If not then you may not have destroyed all the nitric.

Try dissolving your SMB in warm distilled water first and slowing add to the solution.

 

[Charles Connor]

Also there are sometimes when the reaction of the AR with the scrap gets really hot that looks like if you were boiling your solution... if this happened to you, let it cool to room temperature, when the AR solution is hot, when adding SMB, the SO2 gas particles will go out of the solution really fast and will not precipitate gold as wanted... also try the urea process as mentioned in the upper post.

 

[pattt]

Hi,

This is something I remember from when I started reading the forum , from one of The most experienced members here and I always have to think about this when I see Urea mentioned somewhere in a new post.

Quote
"Urea will destroy NOx gas in solution but it will not destroy nitric acid or nitrates dissolved in solution, you will read many places on the internet and in very early posts on the forum suggesting its use to denox or remove excess nitric acid from a solution containing gold, most of the forum has decided urea is not good for this purpose, with PGM's it can form complexes making recovery difficult if not impossible, urea can form ammonium compounds in solution thus has a possibility of forming a possible explosive mix in your treatment or in your waste, it has been reported causing spontaneous combustion in the lab, urea nitrates are not something that should be taken lightly especially with metals and possible ammonium compounds being formed, urea in my opinion is only good to use a prill or to to test the solution, but is useless to just plain dangerous to use otherwise."
Unquote

I would use Hoke's way anyday

Pat

 

[alvaschein]

Hi
I had similar problems when I made my very first batch. At the ending I had a soup of ...??? I don't know what. Anyway, I boiled all down and the remaining salts are awaiting further treatment.
I decided for the future batches to follow Hoke's advice of boiling the solution until syrup consistency and to add HCl to remove all excess nitric. Adding SMB is then very easy and within hours you can see a result (deposited brownish gold powder).

Roy

 

[steyr223]

You used the word boil and boiling
Good way to loose values.

Steam it just below a boil to allow evaporation


This can take 24 hours or more , and is the most
Tedious job I have ever done.

Read Holke's ,she tells you exactly what to do
very near the start of the book
Use the search for dnox or d nox

PS I believe she says add sulfuric (concentrated)acid
to rid nitric not hcl
hcl is added to dilute and bring back up to a workable
Level
Hope this helps steyr223 rob

 

[Charles Connor]

I have always use the urea in my lab and i haven't had any exlosion, also the Hoke method seems a little bit complicated, so the best way for newbies is the urea, in my opinion...

 

[butcher]

I just have to disagree.

The best way for newbies is to study the forum and learn, how to process the gold, making it less difficult to get the gold back out of solution.
Use minimum amount of nitric needed.
Consume nitric acid with gold.
Minimum acid or solutions, gives less acid to evaporate to denoxx.
Evaporation process as taught in Hokes book.
Sulfamic acid.

Urea will only cause the newbie problems, can lead to a dangerous situation or lose of valuable metals, if they think they need to use it, then they do not know how use aqua regia to refine their gold.

There is nothing complicated about it, and it does not need to be a complicated or time consuming process, once you understand it.
Education is the key.

 

[Charles Connor]

this could be compared with the precipitants, them all work on different way, its the method that best fits you and with wich you feel secure ... if urea were that bad, then why is a method mentioned in other refining books just as good as the CM.HOKE as one alternative, and yes it is excellent if you could learn doing all the process mentioned on the forum that would be awesome, but I am one that says that urea does work despite all the negative things that are said...

 

[jimdoc]

this could be compared with the precipitants, them all work on different way, its the method that best fits you and with wich you feel secure ... if urea were that bad, then why is a method mentioned in other refining books just as good as the CM.HOKE as one alternative, and yes it is excellent if you could learn doing all the process mentioned on the forum that would be awesome, but I am one that says that urea does work despite all the negative things that are said...

What are you a urea salesman?

 

[FrugalRefiner]

this could be compared with the precipitants, them all work on different way, its the method that best fits you and with wich you feel secure ... if urea were that bad, then why is a method mentioned in other refining books just as good as the CM.HOKE as one alternative,

Charles, I also have highly regarded books that endorse the liberal use of mercury. Times have changed. We have learned more. In many cases, we've found better ways.

and yes it is excellent if you could learn doing all the process mentioned on the forum that would be awesome

Why do you say "if" you could learn? Read.

I am one that says that urea does work despite all the negative things that are said...

That position will put you in conflict with the Moderators of this forum who do their best to stop the spread of outdated, mis-information.

Dave

 

[NobleMetalWorks]

THIS!

I just have to disagree.

The best way for newbies is to study the forum and learn, how to process the gold, making it less difficult to get the gold back out of solution.
Use minimum amount of nitric needed.
Consume nitric acid with gold.
Minimum acid or solutions, gives less acid to evaporate to denoxx.
Evaporation process as taught in Hokes book.
Sulfamic acid.

Urea will only cause the newbie problems, can lead to a dangerous situation or lose of valuable metals, if they think they need to use it, then they do not know how use aqua regia to refine their gold.

There is nothing complicated about it, and it does not need to be a complicated or time consuming process, once you understand it.
Education is the key.

The best way to deal with problems is to be pro-active not re-active.

I wish that the entire subject of UREA was removed and not allowed on the forum. The only time I believe it's proper to speak of UREA is in regards to scrubbing systems. And even then, only under the proper conditions using the proper equipment. As has been stated, you could be producing dangerous complexes in solution that may be explosive. I personally know a refiner who added UREA to a AR solution that contained gold and PGMs and unknowingly created an explosive complex that did react, and blew his beaker to tiny little pieces. Fortunate for him he was doing this in a 5 gallon plastic bucket in case of a violent reaction that would bubble solution over the sides of the beaker.

this could be compared with the precipitants, them all work on different way, its the method that best fits you and with wich you feel secure ...

It's not what method you "feel" secure with, it's which method is "safe" and best if it's the 'safest" method. There is the way you can do it, and there is the right way of doing it. Instead of telling people what they might can do, why not tell them what they should be doing instead?

if urea were that bad, then why is a method mentioned in other refining books just as good as the CM.HOKE as one alternative

If Cyanide is so deadly why do some processes use Cyanide? If AR is so dangerous, why is it used to refine gold. Everything we do, every way you can possible conceive of processing, recovering, refining gold all have safety concerns and all can be incredibly harmful. Why suffer an unnecessary risk? Why not instead reduce the risks as much as possible? Just because a book that someone wrote states to use UREA, does not mean it is the best method nor practice. Your argument does not make sense. Just because a book states something does not make it true, nor the best method.

and yes it is excellent if you could learn doing all the process mentioned on the forum that would be awesome, but I am one that says that urea does work despite all the negative things that are said...

It's not "if you could learn" it is more like what you need to learn before you start to process material of any type. The correct way should be learned and advised. The process Butcher laid out is the correct and safe way of processing. If you read a book on refining, the recipe for creating AR usually advises to mix specific amounts of HCl with HNO3. Yet this is not the way we do things, instead of practicing chemistry by recipe, we practice chemistry more often by small additions, and observation. Meaning instead of mixing a traditional solution of AR intended for cleaning lab glass, we instead only add as much HNO3 as needed, making small additions until the desired dissolution of the gold has been achieved. Following Hokes suggestions will easily remove whatever HNO3 might be left, using Butchers suggestion of adding a known quantity of gold into the solution will ensure there is no HNO3 free, or it will use up whatever is left in solution.

I don't feel you are trying to purposefully lead people in the wrong direction, but the simple fact of the matter is that if you are doing things correctly, in the way that has been suggested by others, you will not need UREA, and that is the best possible scenario.

Scott

 

[rickbb]

So I'm guessing from the tone of the posts that urea is out and the forum's perfered method is to triple evaportate or use sulfamic acid.

Adjustments will be made then.

 

[Charles Connor]

I had this same situation with other topic of getting the silver out of silver nitrate, when i wrote that adding NaCl to it and then melting the AgCl would be an easiest way, everybody was like *... no that way is dangerous, do not suggest if you dont know the cons or the dangerour part, read HOKE`s book...* its one way that even CM HOKE mentioned on her book, so whats the point of sharing in the forum... im not making anybody change its methods of gold or silver recovery , it`s information based on what i have done or experienced, also i dont know how you people thought the tone im writing was, since writing has no tone unless its expressed to make it seem like one...

 

[NobleMetalWorks]

I had this same situation with other topic of getting the silver out of silver nitrate, when i wrote that adding NaCl to it and then melting the AgCl would be an easiest way, everybody was like *... no that way is dangerous, do not suggest if you dont know the cons or the dangerour part, read HOKE`s book...* its one way that even CM HOKE mentioned on her book, so whats the point of sharing in the forum... im not making anybody change its methods of gold or silver recovery , it`s information based on what i have done or experienced, also i dont know how you people thought the tone im writing was, since writing has no tone unless its expressed to make it seem like one...

Since you posted here, and not in the other thread, I am going to try to answer you here.

You stated:

It is much better to precipitate the gold with SMB to get it without impurities, from what i know, the copper is used to cement the silver out of solution, but it is much better with NaCl...

If you have learned about the reactivity series, you would also know that all values below copper will cement on copper.

It also sounds as if you are suggesting that silver would be in an AR solution in the form of silver nitrate, which is not true. It would be in the form of insoluble silver chloride. You were corrected directly after. It wasn't a big deal, if you read the correction you might understand where your statement is wrong. Copper is not only used to cement silver, but can also be used to cement all values on the reactivity series below copper.

You also stated it is much better to use SMB. That might be true in some situations, but also might be true that copper is better. If you are washing, incinerating and then digesting all base metals in HNO3 after cementing with copper, then it might be better, specially considering that if you are precipitating out of a dirty solution you are going to have drag down anyway.

You then stated:

The NaCl is the cheaper way to get the silver, also the purity will be the same if it is nitrate or chloride, as a chloride just by melting it you get your silver, it is not a difficult process, also to waste gas and oxigen to melt this silver, it is better to have a big ammount to be worth

This is confusing, lets clarify it a bit. If you have a solution of silver nitrate and you add NaCl you produce AgCl, which needs further processing. What you are saying is that the method will produce silver of the same purity as cementing on copper, and is cheaper. I would beg to differ with you on this point. If you have a choice of precipitating silver as silver metal directly out of solution by cementing on copper, or precipitating silver chloride which takes more steps to turn into elemental form, and then needing to refine both because they are not of high purity then it would seem cementing on copper would be less expensive. Not only that, but you stated "as a chloride just by melting it you get your silver", this is not true. You don't just melt the silver, you have to reduce the silver chloride to it's metallic form. The better ways do not produce gases that could be dangerous. If you are reducing by the method C. M. Hoke suggests, then you are using a specifically formulated flux to reduce silver chloride to silver metal. According to Hoke you should use a graphite crucible which is not cheap, you cannot fill more than half full, you have to heat it carefully so you don't have a boil over, you have to do this in a gas furnace, then you have to add more chloride/flux mixture, etc etc etc. If you want to know more you can re-read Hoke. But this process is not nearly as safe, it takes equipment that is much more expensive, you are expending more energy, plus you have to be well experienced in pyrometallurgical processes in order to do this successfully. You should not, not ever, directly melt silver chloride or attempt to do so. You were corrected, and rightfully so. Hoke never stated anything about directly melting silver chloride to silver metal, but rather reducing it via a pyrometallurgical process with a correctly formulated flux and process.

You went further to state:

I have already done this process before, the silver does not comes pure after all this process is done, if refered to the harmful part is the chlorine gas...

If you did use this process I would like to know exactly how you did so. You seem to think it's easier to use this process than to cement directly on copper, or use another more commonly used process to reduce AgCl to Ag.

Then you stated:

Im not giving any instructions, what im saying is how i get the silver out of solution based on the question above, im not telling anybody here how to refine, im giving my point of view about these cases... The forum is to share knowlege and experiences when refining gold and other metals, again it is a MUST for the reader to look for the pros and cons and not jumping into the solution and do it... my mistake if i did not wrote the dangerous part of it, but the melting must be done under a good fume...

You incorrectly stated what Hoke wrote, which caused people to feel it necessary to correct you, and rightfully so. Although you are not telling anyone how to refine, you are incorrectly oversimplifying a process that is not commonly used, and is not in fact easy at all.

All of us have posted information that needed correction or constructive criticism. I myself have been corrected and criticized in threads, specially when I feel passionate about something and have carried my point a too far. As a matter of fact in a very recent post, I had stated volts when I meant amps, and needed to correct it. If I am keeping with the professional flavor of this forum, I have to accept when I am wrong or carried things too far, then correct and conduct myself accordingly. It seems to me that this forum was created for people who can behave as adults who can take and give advice and criticism on the subject of precious metals while keeping a professional attitude. If we cannot, the forum will simply degrade into a medley of incorrect and misleading information. This very well could lead someone to make a serious mistake, harming themselves or others in the process, or worse.

Your own post is a good example of the exact reason why your information should be shared. You stated that Hoke suggests your method, and now that information would seem to have been corrected. Have you considered how many people will read your post, and learn from it?

Even when we are wrong it allows an opportunity to be corrected, and in doing so propagates good information that is correct and usable.

Also, reduction of AgCl via a pyrometallurgical process is not nearly as safe as other methods outlined on this forum. Although what Hoke states can be done, it is not the best, most modern way to process AgCl.

Scott

 

[JHS]

Ok,everyone that comes here is told to read hoke.NO one is told that you do not boil.if they read that and do not understand that,that means steam they are reading miss information or at the very least misinterpreting the information.if there are processes that are in hokes book that are dangerous and newcomers read that in hoke and are not for warned,they are being put in harns way.I too have read the info,that Charles spoke of with reguard to silver
i think if someone is directing,they should also warn.
john

 

[jimdoc]

Ok,everyone that comes here is told to read hoke.NO one is told that you do not boil.if they read that and do not understand that,that means steam they are reading miss information or at the very least misinterpreting the information.if there are processes that are in hokes book that are dangerous and newcomers read that in hoke and are not for warned,they are being put in harns way.I too have read the info,that Charles spoke of with reguard to silver
i think if someone is directing,they should also warn.
john

All of that has been warned about many, many times here on the forum.
Especially not "using gasoline for incineration", as Ms. Hoke's book suggests.

Jim

 

[NobleMetalWorks]

Ok,everyone that comes here is told to read hoke.NO one is told that you do not boil.if they read that and do not understand that,that means steam they are reading miss information or at the very least misinterpreting the information.if there are processes that are in hokes book that are dangerous and newcomers read that in hoke and are not for warned,they are being put in harns way.I too have read the info,that Charles spoke of with reguard to silver
i think if someone is directing,they should also warn.
john

All of the processes that are used to recover and refine metals are dangerous, every single one, even the ones that don't seem very dangerous are.

The information about reducing AgCl by a pyrometallurgical process is dangerous, but it can be done if the correct precautions are used. But that is IF you have the proper equipment, IF you are using the correct flux, IF you are using the correct crucible, IF you are using the correct gas furnace, IF you are following the instructions properly and you understand the metallurgical process, and have experience in pyrometallurgical processes. Charles oversimplified these instructions and incorrectly stated "melting" when he meant to say "reducing", he suggested that precipitating AgCl and then MELTING it was an easier process, which is not in fact true. You should never MELT AgCl, you should REDUCE AgCl. Hoke states very clearly a flux recipe, and that it's a process of REDUCTION, not directly melting AgCl into metallic form.

So Hoke was right, Charles was wrong. You have now stated that Hoke has suggested something dangerous, and yet everything that has anything to do with recovering or refining metals is dangerous. But I want to make this clear, Hoke is not wrong on this point, it can be done in the way she describes but Charles misrepresented the material, and correction was rightfully posted. Also, there are other alternative methods Hoke suggests before giving instruction on the pyrometallurgical process of reducing AgCl to Ag.

People harp and harp about reading Hoke, and also rightfully so. If you read, and understand the language Hoke uses you can more effectively talk about these processes. It's stated over and over and over again, I am not sure how anyone that spends anytime reading this forum can miss this point. If you read and understand Hoke, you will also understand the difference between melting and reduction. They might seem like the same thing, but their differences become apparent when issues like this arise. Understanding the terms, and how to use them properly is important. Specially if you want to effectively communicate with other people on this forum, in an effective way.

Scott

 

[Harold_V]

So I'm guessing from the tone of the posts that urea is out and the forum's perfered method is to triple evaportate or use sulfamic acid.

Adjustments will be made then.

I'd like to make a couple comments, one on the notion of "triple evaporate". That simply isn't good advice. There is no guarantee that three evaporations will expel all free nitric, no more than there is a guarantee that washing one's gold for a given period of time will remove all contaminants that are contained within. I'll address the washing procedure first.

The washing procedure that is recommended on this board is the one I proposed, used and perfected years ago. It isn't a timed process, but one of making observations. One washes until there is no change---not for a prescribed period of time--as that may be as little as a couple minutes---or as long as an hour. How dirty your gold is, and how it precipitates dictates the outcome, not the clock.

The prudent refiner evaporates until there are no familiar brown fumes emitted when HCl is added to a well evaporated gold chloride solution. My experience dictates that the solution will be very dark red, and will have thickened to some degree, before the addition of HCl does any good. With that in mind, one time may be adequate, and four may not be enough. You can not set a hard and fast rule, as it is highly unlikely that you will experience identical solutions time and again. Learn to judge the condition of your evaporation by observing the expected reactions, or lack thereof, not by counting.

If you have doubts about having evaporated properly, introduce a small button of gold of known weight, which will consume any free nitric. That, of course, depends on if you have fee HCl present. Add a little to ensure you do. It does no harm, unlike free nitric.

Harold