I lost 7g of gold

[nickton]

While I agree with you Dave 100% that is how one should proceed from the very beginning in order to get himself out of this mess (correct me if I am wrong) First add some Hcl to see if the white powder is dissolved (maybe add about 50ml) If it doesn't dissolve filter the solution to separate the powder save it until you recover your 7 grams of gold. Then he should evaporate the Aqua Regia solution down till it is a syrup like consistency then add Hcl up to where his original volume was (watching to see if there is brown fumes) then continue this process until no more brown fumes can be seen then double the solution volume with water (distilled water is prefered) then proceed with adding the calculated amount of smb (I would add 9 grams). Now the real question is since he has been a member since 2008 why did he make this simple mistake in the first place. My suggestion is to read the forum on safety and disposal of the waste since he obviously hasn't studied very much in the last 11-12 years.

The doubling your solution volume with water part of this rings an alarm in my head. I remember a post a while back about too dilute a solution before dropping causes problems because the precipitated gold becomes too fine. The advice was to evaporate most water and get a smaller amount of liquid before dropping the gold, or simply not to dilute it at all--if I recall correctly...

-just an observation.

 

[FrugalRefiner]

While I agree with you Dave 100% that is how one should proceed from the very beginning in order to get himself out of this mess (correct me if I am wrong) First add some Hcl to see if the white powder is dissolved (maybe add about 50ml) If it doesn't dissolve filter the solution to separate the powder save it until you recover your 7 grams of gold. Then he should evaporate the Aqua Regia solution down till it is a syrup like consistency then add Hcl up to where his original volume was (watching to see if there is brown fumes) then continue this process until no more brown fumes can be seen then double the solution volume with water (distilled water is prefered) then proceed with adding the calculated amount of smb (I would add 9 grams). Now the real question is since he has been a member since 2008 why did he make this simple mistake in the first place. My suggestion is to read the forum on safety and disposal of the waste since he obviously hasn't studied very much in the last 11-12 years.

The doubling your solution volume with water part of this rings an alarm in my head. I remember a post a while back about too dilute a solution before dropping causes problems because the precipitated gold becomes too fine. The advice was to evaporate most water and get a smaller amount of liquid before dropping the gold, or simply not to dilute it at all--if I recall correctly...

-just an observation.

Everyone has their own procedures that work for them. I would probably do a few things differently, but that's just me.

When evaporating AR to syrup, I don't add enough HCl to reach the original volume. A small amount will suffice to expel excess nitrates as NO_x gasses (brown fumes) and avoids having to re-evaporate as much solution and HCl. Repeat as needed till no more (or minimal) NO_x is seen.

What you do next depends on the feedstock and your subsequent processes/preferences. Harold would drop the gold from a concentrated solution, but he still added ice that would dilute his solutions while cooling them, then include washes with ammonia to eliminate any silver that was still in the concentrated solution. GSP would dilute to three times the volume to precipitate the silver, filter it out, then drop the gold.

I agree that gold dropped from a concentrated solution will usually agglomerate better and settle more quickly, while that dropped from a dilute solution will be finer and take longer to settle. But some of that depends on how much solution you're starting with. If you've evaporated your solution to a syrup, tripling the volume still doesn't give you a lot of solution. If you've dissolve a couple of grams of gold in a liter of solution, you'll have a very fine precipitate.

It's all a matter of experience and preference. We all develop processes that work for us.

Dave

 

[nickton]

I found the post I was referring to:

Re: Precipitate+Heat.........
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Post by FrugalRefiner » April 29th, 2018, 11:56 am

Heat and agitation help. Precipitating from a concentrated solution also helps. Gold reduced from a dilute solution will have a more difficult time agglomerating into large particles that will settle quickly. The extreme example of this is a solution in which the gold forms a colloid, which may never settle until the colloid is broken.

Dave
Printer friendly copy of C. M. Hoke's Refining Precious Metal Wastes.
Screen readable copy of C. M. Hoke's Refining Precious Metal Wastes.

 

[jarlowski1]

Ok so yes if he had 3 liters of solution and evaporated that down to a syrup then yes add hcl to original volume would not be conducive to be dropping gold from, but if you go back to he had stated that the solution was about 200ml in total containing 7 grams to me that is a pretty decent concentration and if you boiled that down to a syrup and added hcl to get rid of the nitric in solution then boiling again an so on until the last addition came up with no fumes, raising this to the original volume would be 200ml containing 7g of gold even if you doubled that to 400ml that solution would still be concentrated enough to precipitate and settle with no issues and gold particle size would be just fine.

 

[FrugalRefiner]

Yes, I'm not trying to disagree with anyone. All situations are different.

My dad was a machinist. When he would make a drawing and try to show an angle or a relationship, he would always draw it in an exaggerated example, then always say "this is exaggerated", hence my example of a couple of grams of gold in a liter of solution. The OPs solution was somewhere in between.

But 7 grams of gold can be dissolved in less than 30 ml of HCL and less than 10 ml of nitric. 200 ml is still far more than needed. If I evaporated it down to a syrup, I still wouldn't add enough HCl to bring it back to 200 ml.

Dave

 

[Shark]

It's all a matter of experience and preference. We all develop processes that work for us.
Dave

I think that is the key to what Dave is saying. I find myself more often doing a project with a plan that will change based upon what I see and/or how a solution reacts. Often on my small scale it can be as simple as being out of a needed chemical, so instead of using HCl and nitric, I may use HCl with bleach or a nitrate fetilizer or a stump remover. I have found when doing gold filled I prefer to use poorman's nitric over "store bought" on medium sized lots but the amount of silver involved can change that plan back to the store bought.

As for diluting AR, it depends on if I am in a recovery stage or a straight refining stage. Even then it all depends on what I am seeing as the job progresses. A few years ago, it would have been straight by the book, even if knew there would be a headache at some point. Time and experience along with reading the forum, and books, can teach us when a change can be safely made. Often we forget that after a drop the next step is washing or cleaning our resulting metal powders. This can also play a big role in when we or how we begin the refine and how we proceed. I don't like to use ammonia, so often I will dilute a refine where with a recovery I often drop from a concentrated solution. Based on what metals went into the AR and what I am seeing determines which I use as well.

There are many ways to accomplish a given job, it all depends on who is doing it and their level of comfort and experience. Because we do it differently does not mean one is right and one is wrong. If it produces the required purity, it should all be good.

 

[jarlowski1]

I totally agree with both of you Shark and Dave. And Yeah Dave I probably would not bring the HCl back up to the 200ml mark either. I was more or less trying to clear up any confusion on what I originally wrote since nickton mentioned something about it. If the OP follow my instructions 100 times (exaggerated) eventually he would begin to understand what he is supposed to be looking for. In this case the absence of NOx gases and thus would begin to find his own way of doing things. Hopefully he would understand not to use way too much nitric in the first place.

On a side note Dave my father is a machinist as well; it truely is a dying trade...

 

[goldenchild]

I was never a fan of evaporating to remove excess nitric. It takes too long and I'm too impatient for it. I always like using nitric short of enough to digest all the gold and then adding very small amounts at the very end. Doing it that way you can use urea to remove the tiny bit of excess nitric in solution. For the first refining you could even use smb to remove the excess nitric.

On the second refining is when I use ice to bring down any silver left in solution. If you did everything right on the first pass there should be little to no chloride. Filter the solution (no matter what) and drop the gold. If your solution happens to drop the gold too finely for your taste simply heat the solution (hot). It will bring everything down fast and clump it all up very nicely.