I forgot to neutralize! , help me please
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Sulfamic acid ( grout cleaner in the hardware section) and using the heat of evaporation as mentioned in Hoke's book, the sulfamic acid produces some sulfuric acid which can precipitate lead as a sulfate, the lead salt will need to be separated from the solution before precipitating the gold, the added benefit of sulfuric acid is it will help drive off free nitric acid from the solution.
If you do not have sulfamic acid a little addition of sulfuric acid and heating to evaporate as mentioned in Hoke's book will also do the trick.
Adding a button of gold (Harold's trick), and using heat and evaporation to drive the nitric from solution as advised by Miss Hoke as she describes in the evaporation process.
If you do not have sulfamic acid a little addition of sulfuric acid and heating to evaporate as mentioned in Hoke's book will also do the trick.
Adding a button of gold (Harold's trick), and using heat and evaporation to drive the nitric from solution as advised by Miss Hoke as she describes in the evaporation process.
Denisse, please don't double post.
I have removed your other post.
Göran
I have removed your other post.
Göran
Not a big problem , double the size of you aqua regia solution by tap water because gold loves to precipitate from diluted not concentrated solutions ,
You can eleminate the nitric using many ways :
1- nitric elemination by urea : (not recommended)
heat your aqua regia for couple minutes until it is warm
add urea to the aqua regia, small spoon firstly a strong fizzing will start, wait until its finished then stir slowly
Add another small spoon if nitric is still there, strong fizzing will happen again wait until its finished and stir slowly again, repeat those stips until you notice that the fizzing is very weak, there are many videos explaining the nitric elemination by urea
2- nitric elemination by sulphamic acid :
same as above but replace urea with sulphamic acid
3-nitric elemination with evaporation.
4-nitric elemination with iron sulphate (recommended becausr This way will both eleminate the nitric and precipitate the gold)
after you eleminate the nitric filter the solution and drop your gold with SMB or iron sulphate
You can eleminate the nitric using many ways :
1- nitric elemination by urea : (not recommended)
heat your aqua regia for couple minutes until it is warm
add urea to the aqua regia, small spoon firstly a strong fizzing will start, wait until its finished then stir slowly
Add another small spoon if nitric is still there, strong fizzing will happen again wait until its finished and stir slowly again, repeat those stips until you notice that the fizzing is very weak, there are many videos explaining the nitric elemination by urea
2- nitric elemination by sulphamic acid :
same as above but replace urea with sulphamic acid
3-nitric elemination with evaporation.
4-nitric elemination with iron sulphate (recommended becausr This way will both eleminate the nitric and precipitate the gold)
after you eleminate the nitric filter the solution and drop your gold with SMB or iron sulphate
kurtak
Well-known member
sayf said:
That just is NOT TRUE :!:
Gold will precipitate from solution whether it is concentrated - or dilute :!:
The more concentrated the solution is the larger the gold "particles" will be when they precipitate which in turn means the better/faster they will settle
The more dilute the solution is the smaller the particles will be which in turn means slower settling of the particles
There is absolutely no reason why you can't precipitate your gold from a "fully" concentrated solution of AR --- provided there is no "free" oxidizer in the solution (free oxidizer is what cause's the gold to not drop)
In fact - dropping gold from a "fully" concentrated solution (provided there is no free oxidizer) will cause the gold to drop so fast (due to large particle size) the gold will pile up in the bottom of the beaker & trap gold chloride (dissolved gold) in the gold powder settling in the bottom of the beaker --- therefore you need to stir the settling powder up to bring the gold chloride up out of the settling gold to insure all the gold chloride gets reduced to gold
That said - diluting to double the volume of your concentrated AR wont effect the particle size enough to cause settling problems - whereas "over" diluting may/can cause settling problems --- the more dilute - the smaller the particle size - the longer it takes to settle
Also - the gold that precipitate last from the solution will be smaller then the gold that precipitates first --- so - the more dilute the solution is - the smaller those last precipitated particles will be --- in other words - if the solution is VERY dilute the particles that precipitate last can be so small that they can take a day or more to settle
Now then with all that said - there are reasons for diluting AR to double the original concentrate
Concentrated acid (to a point) does a better job of keeping/holding dissolved metal in the solution then dilute acid
I say to a point because -------------
Example; - HCl (generally speaking) does not dissolve silver & in fact will precipitate silver as silver chloride from a silver nitrate solution --- however - when concentrated - the HCl in the AR will actually allow "some" silver to remain dissolved in the AR - so - by diluting (doubling with water) the AR it makes the HCl weaker & therefore the HCl can no longer hold that "small" amount of dissolved silver in solution & it will drop out as silver chloride which can then be filtered out before dropping the gold - so that (small) amount of dissolved silver doesn't co-precipitate (as chloride) when dropping the gold
In fact - IF - SMALL amounts of silver chloride co-deposits with your gold - a "concentrated" HCl wash will re-dissolve that SMALL amount of silver chloride (thereby cleaning up the gold) - the concentrated HCl can then be diluted to drop the silver chloride
Like wise - this is true with "some" (other) base metals - therefore - with very dirty base metal solutions diluting (by double) can/may allow "some" dissolved base metal to drop out & be filter before dropping the gold thereby again allowing for "less" base metal drag down from really dirty solutions --- & again is why we do concentrated HCl washes to clean up any small amounts of base metal drag down
As a note; - tin tends to act somewhat like silver
Also - with SMB - "some" water in solution "helps" to keep the SO2 (gas) in solution - so if the AR is "concentrated" it is better (but not needed) to dissolve the SMB with "some" water first - if the AR has been diluted you can put the SMB in dry
Bottom line - though diluting is not "needed" to precipitate gold - it is done for the reasons above - & if nothing else it ends up getting diluted (to some point) during the filtering process
Kurt
Hello Kurt, you said everything important learning this is happening to me. I made a process with large ceramic CPUs, for sure my AR water was very contaminated with base metals, I made the mistake of putting too much water, the solution before it was too thin, although I used sulfamic to neutralize the nitric, I was not able to precipitate the gold. I used 200ml of HCI to 35ml of nitric acid HNO3 was not very nitric, but the excess water is making it difficult to precipitate. Thanks for the information I will work on the recovery and learn more. Thank you my friend I am learning a lot on the forum.
Attachments
I have a question about a similar problem.
I made my AR with 350 ml HCI + 40 ml HNO3. There was the filter paper in the beaker that i filtered from a dirty solution. Simmered like 5 minutes. Gold&base metal dust dissolved completely. It was a sweet dark yellow colour, UNTIL, silly me, add a table spoon of urea. So the solution became light green... I did stannous test, and there wasn't a black (not even a light brown) colour. Added SMB anyway. A few black clouds took shape and dissappeared immediately. Still light green and no trace of gold.
How can i recover that?
I made my AR with 350 ml HCI + 40 ml HNO3. There was the filter paper in the beaker that i filtered from a dirty solution. Simmered like 5 minutes. Gold&base metal dust dissolved completely. It was a sweet dark yellow colour, UNTIL, silly me, add a table spoon of urea. So the solution became light green... I did stannous test, and there wasn't a black (not even a light brown) colour. Added SMB anyway. A few black clouds took shape and dissappeared immediately. Still light green and no trace of gold.
How can i recover that?
Two comments:
First, urea doesn't really eliminate excess nitric acid. While some professionals use it, they have the experience to know when and how much to use. To eliminate excess nitric, go to the hardware store and look for grout cleaner that is sulfamic acid. It will serve you much better.
Second, you really never want to see a brown color when testing with stannous. Gold will be anywhere from a faint purple to dark purple to black depending on the concentration of gold in the solution. Brown (often referred to as a false positive) usually means you've added too much SMB to a solution that has copper in it. The brown is caused by copper, not gold.
The fact that you saw "a few black clouds" that disappeared means you still have excess oxidizer in your solution. The gold is being reduced to metallic gold (the black cloud), but then it's being redissolved by the excess nitric.
If you have SMB that has settled to the bottom of your beaker, you may need to add some HCL.
Get some sulfamic acid, use it to deNOx your solution, then see what happens.
Dave
First, urea doesn't really eliminate excess nitric acid. While some professionals use it, they have the experience to know when and how much to use. To eliminate excess nitric, go to the hardware store and look for grout cleaner that is sulfamic acid. It will serve you much better.
Second, you really never want to see a brown color when testing with stannous. Gold will be anywhere from a faint purple to dark purple to black depending on the concentration of gold in the solution. Brown (often referred to as a false positive) usually means you've added too much SMB to a solution that has copper in it. The brown is caused by copper, not gold.
The fact that you saw "a few black clouds" that disappeared means you still have excess oxidizer in your solution. The gold is being reduced to metallic gold (the black cloud), but then it's being redissolved by the excess nitric.
If you have SMB that has settled to the bottom of your beaker, you may need to add some HCL.
Get some sulfamic acid, use it to deNOx your solution, then see what happens.
Dave
I use urea all the time when I am refining. I literally put a few grains in the solution. If it fizzes there is excess nitric. So I add a pinch at a time until the reaction stops. A tablespoon to such a small volume is beyond me.
ZiegenSauger
Well-known member
- Joined
- May 18, 2020
- Messages
- 73
I prefer to never have excess Nitric. I go incrementing after a calculated first load.
There are exceptions though depending on the scenario, my goal, or some change in between.
I use both, either Urea or Sulfamic, also depending on the scenario.
My preferred is always drop placer gold bits to the final, filtered, clean gold impregnated solution. Depending on how fast or how slow it goes. More or less I always have some bits of gold for a final and clean SMB treatment.
A question: has anyone tried to drop gold re-using a previous saturated SMB solution from where Gold was already dropped????
It came to my mind now. I just dropped Gold from my stockpot. The first SMB saturated solution went to the temp container (I use transparent 1 L plastic bottles from grape juice as temp. for each SMB drop and keep for a month before transferring the contents to the bucket).
I have my last batch of the week in AR now. I will try to re-use that saturated SMB.
Please comment, I am curious now.
There are exceptions though depending on the scenario, my goal, or some change in between.
I use both, either Urea or Sulfamic, also depending on the scenario.
My preferred is always drop placer gold bits to the final, filtered, clean gold impregnated solution. Depending on how fast or how slow it goes. More or less I always have some bits of gold for a final and clean SMB treatment.
A question: has anyone tried to drop gold re-using a previous saturated SMB solution from where Gold was already dropped????
It came to my mind now. I just dropped Gold from my stockpot. The first SMB saturated solution went to the temp container (I use transparent 1 L plastic bottles from grape juice as temp. for each SMB drop and keep for a month before transferring the contents to the bucket).
I have my last batch of the week in AR now. I will try to re-use that saturated SMB.
Please comment, I am curious now.
in theory, it is possible. anyway it depends on how pure was the gold solution from which you were dropping the gold. because the base metal impurities and other things will be added to your fresh batch.
second, the best is not to use large excess of SMB either. from my point, SMB or sodium sulfite as reducing agents are cheap for me, so i dont bother with any sort of recycling
nice things being said here, I wonder what kind of oxidizers could be in AR which will prevent precipitation and if you can explain the mechanism by which it prevents precipitation, I am trying to learn
This is maby helpful to someone.
I had a solution (about 1l to 1 1/2l) with just 0.3g of gold in it.
It was dilluted and took 3 to 4 days to settle out.
Martijn
Well-known member
Nitric acid, it dissolves the gold before it can settle out. As I show in this video.
If there's not too much, SMB will do the trick.
I have just found this in the Hoke's book: Premixing Aqua Regia - In Hoke’s day it was common to premix aqua regia in a fixed ratio, then to combine it with the metal. While others have developed similar techniques, GoldSilverPro has championed the cause of adding nitric acid in increments. It is far better to add only the amount of nitric needed to perform the task than to add too much and have to deNOx after the metals have been dissolved.
