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R

rich_2137

Well-known member
Joined
Jan 28, 2012
Messages
127
Location
England, Nottingham
Hi all
Just wondering if gold be dropped with SMB if excess nitric it in the solution?
As I've just dissolved some gold powder with AR and then dropped the gold using SMB, left it a day or so and now it's redisolved!? but I thought SMB wouldn't work if you have free nitric in the first place? Any help would be great!

Cheers
Richard
 
i have seen it re-dissolve when i thought i had used up all the nitric. it looks like a nice drop and then you see it dissolve. especially if you have a big volume of fluid your working with. it only take's 1ml of nitric to dissolve a gram of gold. i try and remember that. a little pinch of sulfamic will take care of it. or sometimes even another addition of SMB.
 
You've been a member this long and have not read about redissolving gold drop?

SMB drops gold, Excess nitric + HCL redissolves it. You could do that back and forth untill nitric runs out is my guess. Or add more gold untill no more dissolves.
Or, evaporate to a syrup, add HCL, evaporate, add...etc. just like described in alot of posts on here.

B.S.
 
I didn't realize, that you wrote, you ask for help in your last sentence, sorry for my short answer above. It was just in my eyes a valid answer to one of your questions.

How much excess nitric do you expect to have in your solution? If it is only a little, I would prefere gold button method. If it is a lot, I'd use sulfamic or evaporation. Going on with additions of smb would not be a good option. This will co-precipitate impurities, the last gold comes very slowly down and itis wasting smb.
 
Pantherlikher said:
You've been a member this long and have not read about redissolving gold drop?

SMB drops gold, Excess nitric + HCL redissolves it. You could do that back and forth untill nitric runs out is my guess. Or add more gold untill no more dissolves.
Or, evaporate to a syrup, add HCL, evaporate, add...etc. just like described in alot of posts on here.

B.S.
Click to expand...

Hi
Yes I have been a member hear for a while and no I haven't heard of it otherwise I wouldn't of posted this!
I'm only just starting to understand the AR process as I usually only us AP and HCL/CL as I'm am very confident in process and have been successful in my yields!
 
solar_plasma said:
I didn't realize, that you wrote, you ask for help in your last sentence, sorry for my short answer above. It was just in my eyes a valid answer to one of your questions.

How much excess nitric do you expect to have in your solution? If it is only a little, I would prefere gold button method. If it is a lot, I'd use sulfamic or evaporation. Going on with additions of smb would not be a good option. This will co-precipitate impurities, the last gold comes very slowly down and itis wasting smb.
Click to expand...

I don't think there is much as it's took several days to redissolve,the gold powder plus the solution was left a week or so before adding SMB
I'll try adding sulfamic first, thanks for the advice

Rich
 
So...you're saying you have not done and research on AR?
A simple search of "excess nitric" brings up alot of results. The first bunch I just found indicate ways of testing and ridding the solutions of excess nitric acid.

Not being mean or snobbish or anything but it's a question a "newbie" that does not bother to read and learn would ask.

Following the directions exactly...4HCL- 1Nitric acid ratio is too much. Several posts state it's better to add nitric alittle at a time and wait for reaction to stop...

As well as the answer to rid excess nitric...

B.S.
...I'm still reading and learning the AR process and wont attempt it yet...
 
I'm not saying I haven't done it before , I've been successful s few times with AR and I do understand the process I've just never came across this before so I've had no need to research it, Sorry if I'm not allowed to ask for a little help and you seem to be going off what my original question was but in don't matter now anyway!
 
rich_2137 said:
I'm not saying I haven't done it before , I've been successful s few times with AR and I do understand the process I've just never came across this before so I've had no need to research it, Sorry if I'm not allowed to ask for a little help and you seem to be going off what my original question was but in don't matter now anyway!
Click to expand...


Hi rich, dont be discouraged, try the sulfamic acid to get rid of the extra nitric, then try drop with smb again
remember that it only takes about 1ml to dissolve 1 gram of gold of excess nitric in AR

the next time you make your AR ad the nitric slowly with a pipette or eye dropper
 
rich_2137 said:
solar_plasma said:
but I thought SMB wouldn't work if you have free nitric in the first place?
Click to expand...

Well, actually it didn't work, if the gold redissolved, right?
Click to expand...
Thanks that was really helpful!
Click to expand...

The best way to remove excess nitric acid is :
Put the aqua regia solution into a big evaporating dish. Now add a little sulphuric acid, stirring all the time, and working slowly, as it might spatter. Use about an ounce or less of the sulphuric acid to each quart of liquid. Now boil the solution down gently, to a syrup, being careful not to spatter.

As per the great Hoke.
 
arsenic123 said:
The best way to remove excess nitric acid is :
Put the aqua regia solution into a big evaporating dish. Now add a little sulphuric acid, stirring all the time, and working slowly, as it might spatter. Use about an ounce or less of the sulphuric acid to each quart of liquid. Now boil the solution down gently, to a syrup, being careful not to spatter.

As per the great Hoke.
Click to expand...
Do NOT boil. You will lose values. If you check the introduction in either of the copies in my signature line, youll find a discussion of evaporating vs. boiling.

Dave
 
Hoke used the word boil, when evaporation should have been used, if you read Hoke's carefully you will see that she did not actually mean to bring the solution to a boil, actually she warns against it, She used a steam bath (which was not hot enough to boil the aqua regia solution, pay attention to page 227 Hoke's book (Losses), where she warns against boiling the solution.

Even where she uses the word boil she cautions against spatter of the liquid, (which happens when you boil), on page 44 she talks about the evaporation process and says to lower the heat (before you get to the point of boiling) or spattering the solution, page 55 she says a steam bath is advised (the solution would not get hot enough to boil), page 119 she gives advice on a good temperature (that would not boil aqua regia) and warns do not let it spatter (boil), again on page 147 she advices a large evaporating dish and a steam bath to evaporate (not boil the solution), page 175 evaporation of solution...

Basically evaporate the solution, do not boil the solution where you will spatter your gold all over the lab.
 
butcher said:
Hoke used the word boil, when evaporation should have been used, if you read Hoke's carefully you will see that she did not actually mean to bring the solution to a boil, actually she warns against it, She used a steam bath (which was not hot enough to boil the aqua regia solution, pay attention to page 227 Hoke's book (Losses), where she warns against boiling the solution.

Even where she uses the word boil she cautions against spatter of the liquid, (which happens when you boil), on page 44 she talks about the evaporation process and says to lower the heat (before you get to the point of boiling) or spattering the solution, page 55 she says a steam bath is advised (the solution would not get hot enough to boil), page 119 she gives advice on a good temperature (that would not boil aqua regia) and warns do not let it spatter (boil), again on page 147 she advices a large evaporating dish and a steam bath to evaporate (not boil the solution), page 175 evaporation of solution...

Basically evaporate the solution, do not boil the solution where you will spatter your gold all over the lab.
Click to expand...

Wow, thanks Butcher. It seems you have by hearted the hoke books with page numbers.. :)

Thanks for the info. So what if we boil the AR solution to a very low heat?? At very low heat it won't boil and its as good as evaporation, right?? We can always keep an eye on AR to make sure it doesn't reach boiling level.
 
FrugalRefiner said:
arsenic123 said:
Do NOT boil. You will lose values. If you check the introduction in either of the copies in my signature line, youll find a discussion of evaporating vs. boiling.

Dave
Click to expand...
Click to expand...

Thanks Frugal. I will definately check it.
 
arsenic123 said:
Wow, thanks Butcher. It seems you have by hearted the hoke books with page numbers.. :)

Thanks for the info. So what if we boil the AR solution to a very low heat?? At very low heat it won't boil and its as good as evaporation, right?? We can always keep an eye on AR to make sure it doesn't reach boiling level.
Click to expand...
I think the word you should use is "heat" not boil, and the temperature you should aim for is almost simmering. When there is vapor formed right above the liquid surface but no bubbles formed or reaching the surface that's the sweet spot. When bubbles breaks the surface small droplets are formed and brings small amounts of values with them into the air. There's an interesting story on the forum where one person made a purple stain on the side of his trailer when boiling gold chloride...

Göran
 
I hate to be the guy who keeps asking the
Same question, but there is a very divided
Group about boiling or evaporating

Now i know not to splatter my gold all over the place
I mean i realized all those purple spots on the corningware
Ment something :roll:

Seriously can you boil if you cover with a watch glass so no values splash out,can you loose values any other way.other than splashing out from boiling

I have asked this before amd have read 100's of threads
With both topics some say yes some say no

I think free chemist did an experiment witha large amount
Of au in an enclosed transparent chamber, after boiling the gold you could see the gold all over the chamber very far from the actuall boiling solution

To me it did not look like it was just from splatter but maybe something else

I have put many paper towls over my solution while steaming and tested they have never shown positive
But i am still leary

Thanks steyr223 rob
 
Rob, why are you so eager to boil? Show me a thread where someone is telling it's okay to boil when denoxing without anyone correcting them.

When denoxing a solution we want to get rid of the nitric through evaporation. If we boil the solution there are a lot of small droplets that is created and drifts away as a mist, taking gold with it. It isn't just the big splashes that transports off the gold.
To put a lid on the vessel would let the nitric flow back into the vessel and that isn't what we want to do.

Boiling is a tool that has it's place but not when denoxing. We usually boil AR for dissolving problematic alloys and mixed scrap. This is done because boiling agitates the solution and the added heat makes reactions go faster. But then it is recommended to do it in a boiling flask, a reactor or in a beaker with a watch glass as a lid. AR condenses on the lid or in the neck and flows back into the vessel, keeping the gold in the vessel.

Göran
 
Read Hoke's she discusses this very question.
15 minutes reading the page numbers I gave above for Hoke's book, with what we have discussed here will give you a better understanding of the process.
 

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