Precipitation for newbs

Dear All,

Firstly... ever throw away filter papers for your gold chloride...

I got 4.8 grams from 6 batches of refined karat.

Second....for all newbies... there is nothing more disappointing than going to precipitate and that penny drops that you’ve messed it all up when nothing but a cloud of S02 comes your way....

Please see this link. Use option one/a.

http://www.freepatentsonline.com/3856507.html

I find hydroxide mixed at a far less ratio than they say here to be fine... I use 30 grams per 150ml of distilled water. This raises the ph to around 3 which is what you need for precipitation to occur efficiently. I use this per 500ml of aqua Regia.

As long as you haven’t used a ridiculous amount of excess nitric, it should also kill what’s left. If you are careful with your nitric additions it will

Hope this helped.

No, sodium hydroxide doesn't remove nitric acid, it changes the pH.

If you have excessive nitric it will create a problem for you and SMB doesn't work if the pH is too high. I've precipitated gold from full strength HCl without problem other than the SMB turns into gas really fast. The only time I had problem with SMB was when I had too high pH, the gold came right out when I added HCl.

Patents doesn't have to be correct to be granted, it just have to be somewhat novel. It's also a lawyer describing an industrial process in legaleese so it doesn't make for easy to follow instructions. It is written to block competition from doing something people have done for ages.

Yeah, my view of patents doesn't smell of roses.... :twisted:

Look, if you add lye to nitric acid you neutralize the acid but are left with nitrates in solution. You now have sodium nitrate in solution. If you add acid to that mixture you will form nitric acid again from the nitrates. That's the base (pun not intended) of making poor mans aqua regia.

That's why I always gets upset when people talking about neutralize the nitric acid instead of using the correct word that would be "destroy", "remove", "eliminate", "denox".... Neutralize brings thought to neutralize an acid and the ignorant to add baking powder, sodium hydroxide or other bases to their gold chloride and then we have to clean up the mess here at the forum.

Göran

Thanks Goran....

I too hate lawyers.... we call them solicitors here.... they solicit misery then profit from it.

Back to matters... I do not add lye as such in an aggressive way... I dribble a few millilitres at a time and stir then I check the ph with litmus. The second I get a 3 reading I stop. I never have an issue with salts.

Another thing I do do though, which I know you jedis discourage and I fully intend to stop doing, is I use a drop of adblue until i see no fizzing. I actually do this prior to the addition of lye.

But I struggled in my early days to achieve precipitation and have found my last few batches a lot better using this approach.

Adblue, I guess that's urea?

It works sometimes but if you have used poor mans aqua regia (ie nitrate salt + HCl) then it might not work. I've never used urea myself but I've seen people I admire using it, but only people that used nitric acid and knew what they were doing.

But, if it works for you I might learn something new from your experience.
We are all (many of us at least...) here to share knowledge.

Göran

Adblue is a diesel exhaust treatment, which in most countries marketed, consists of about 35% urea, with the remainder being deionized or other purified water. Percentages differ a bit from place to place.

Time for more coffee.

Galenrog is correct regarding the adblue.

In terms of the hydroxide, I really do add a minimal amount. It’s a trickle, maybe 1-3 ml at a time, stir, check ph and target a 3 reading. I am told by my mentor that 2.8 is optimal.

I have seen precipitation of copper, especially when I made the above button as it was from old dirty papers. However, as long as you maintain an acidic ph the hcl is still strong enough to re-dissolve it upon stirring. It’s visible for less than 10 seconds.

At this point I have added 1/20th of my solution volume in adblue which kills the nitric before raising the ph. Each time I have done this I have had precipitation immediately and I achieve it with a 1:1 ratio of sulfite to expected gold.

I’m fairly open about my beginner mistakes and use of excess sulfite was a problem for me.

Nitric acid and urea (or urea and water diesel exhaust treatment fluid), forms a salt of UreaNitrate.
urea will not remove nitric acid. but it will convert it to a nitrate salt...


https://en.wikipedia.org/wiki/Urea_nitrate

Sodium or potassium hydroxide will not remove nitric acid it converts it to a salt of sodium or potassium nitrate salt and water...
NaOH + HNO3 --> NaNO3 + HOH (H2O)

Hydroxides, alkalines, carbonates...also convert the acidic nature we need into the water, The Acids (hydrogen or hydronium ions) needed for several reasons, besides for De-Noxxing the solution and keeping base metals in solution during precipitation, or when it is needed to provide acid for some other reagent and its chemical reaction we are using in the process...) to water...

H+ + OH- --> HOH (H2O)

These will reform nitric acid in solution with any acid.
NO3 + H+ --> HNO3

So you have added chemicals that will not do the intended purpose and now have salts from those chemicals and reactions... Just more trash in with no work done...

PS I Would be careful about heating and evaporating the solution with Urea-nitrate it could be dangerous to do in glassware...

Both are useless for what you are trying to do and only add other complications...


You would be better off cementing your values out of this mess using copper and spend you time studying.

Thanks Butcher.

I personally have never ever had an issue with salts but I distill my own nitric I don’t use poor ar. I produce pure and dilute.

I use a minimal amount of base; I’m advised by a guy on you lots level that it is the “professional” way of raising your ph and if you know what you are doing you can apparently do this with ease without even litmus just by watching the solution.

I obtain nearly pure gold with this method and therefore see no reason to cement. I only ever cement as a last resort myself.

I will video this process this weekend as I have another dozen filter papers to process. I will video it all from the point when I have finished filtering my AR which is when this process starts.

Again, I do not neutralise anything at all. I merely raise my Ph to an optimal level which is 2.8 - 3.4 i am advised. The denox using this process should really take you less than 60 seconds.

The precipitation should also occur before you’ve even had a chance to scoop that second spoon of sulphite.

As I say I will video and post this for anyone interested. I’m a bit manic trying to build my fume hood right now but will find time this weekend.

I’ve also seen so many discussions centred around why sulphite isn’t dropping gold which then evolves to discussions around temperature of solution which is a waste of everyone’s time.

The solution temp should always be similar to human comfort levels and there really is very little to say on that beyond that. I’ve seen pages of discussions regarding this.... then you have Poe saying crap like “it must be boiling”. Then newbies have the mess of what comes after boiling gold chloride plus potential losses.

I see no reason at all to boil anything after your nitric recovery. I never boil. So many reasons not to.

My point is the ph reading of your AR is important and I see a lot more discussion on temps than this.

You can skin a cat many ways, as you can manipulate Ph. I use hydroxide. A weaker base can be just as affective.

Thanks Butcher.

I personally have never ever had an issue with salts but I distill my own nitric I don’t use poor ar. I produce pure and dilute.

You must not have understood a word I said, You do not know what salts do you?

What does distilling nitric have to do with anything?

Basically all you have if you reacted metals and acids are salts of both...Salts are formed in many different chemical reactions, often the reagents we use are salts themselves when we recover or refine gold we are dealing with salts. all kinds of different salts...

If you have never had an issue with salts then you have never had an issue in recovering or refining gold or any other metal.

I see no benefit in raising pH.

Yes, I can skin wildcats in many different ways, but the best cat hides are always done in specific ways. and processing it with Hydroxide only makes cat leather, the caustic de-furs the hide, and you no longer have a decent cat hide, but I thought we were discussing refining, not de-furring wild cats.

I have not had an issue with salts in the context of the discussion; via denoxing using adblue. I have had salts in my recovery process, sulphate salts due to my cold nitric....

I’ve had lead salts drop out of my AR following sulphuric additions. I have dealt with salts many times.

However not in my process I have described. If I do I will post what I experienced.

Back to the base... unless you were to bring the Ph above 4 which starts to enter neutral zones, precipitation only requires an acidic solution. I have never neutralised my pregnant solution and I use soda to deal with waste. You can use distilled water to manipulate ph. I just prefer base. It’s quicker and keeps your volume down.

And also. I can’t see why you would even need to add heat following the adblue. I certainly have never.

This would be pointless. Once you have dropped gold and tested your solution with stannous, at this point it can be regarded as waste and treated accordingly.

You may even have some base left over to do so.

Many metal salts are water-soluble including gold salts, most all of your solutions are dealing with salts in solution...

You may not see the salts that you get when you add urea to a solution, the explosive salt of urea nitrate is pretty soluble in solution...

What Benefit is there from raising pH? Why.

Why do you believe urea does any good?

II guess I am just wasting my time in this discussion,

Heck lets just dump some carbamide and caustic in there and see if we can get something, anything that might be gold... If that does not work we can always dump in more chemicals its bound to come out sooner or later?



Fell like I am bagging my head against a concrete wall here, I think I go back up in the mountains, I found a nice section of the ancient river bed on top of a mountain close by too here, after running some of the concreted conglomerates through the ball mill and panning the first pan full had four flakes of gold, nothing exciting but better than beating my head up against this wall.

Ok...

So the reason I would do it... is to achieve optimal conditions and therefor outcome. Why would you not if it doesn’t ruin your process and takes you all of 5 minutes?

Why would I ignore someone that I’ve watched for two years produce the best quality gold in London?

Hoke even discusses urea. I hope in the not too distant future my ability to be able to use my experience with nitric additions to avoid it.

The bottom line is it works. And it works well.

Why would I cement everything over days and start over again? That doesn’t make sense when I can use the above method and get nearly pure gold. It’s a waste of time and materials and doesn’t produce you nearly pure gold. You then need to clean, re dissolve, and precipitate which if you aren’t experienced with you’re not going to be able to do the above with excess nitric.

Evaporation is not something for beginners either.

Raising the pH of Ar to around 2.8 (meter reading of 2.5 if I recall correctly) makes the SMB more selective for gold. I've tried it, it works and I mentioned it a few years ago on here.

Edit: It's important to note that I mean denoxxed AR and I don't use Urea.

That given It's not something I do as a rule because I can clean my gold well enough to avoid this step.

It takes one heck of a lot of base to raise a pH 1 solution to pH 2. That I know from pH balancing for Formate precipitation of Pd.

Jmk88 said:

I will video this process this weekend as I have another dozen filter papers to process. I will video it all from the point when I have finished filtering my AR which is when this process starts.

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As I say I will video and post this for anyone interested. I’m a bit manic trying to build my fume hood right now but will find time this weekend.

Click to expand...

I'm looking forward to that. Good luck with your build.

In certain situations urea will work, no doubt about it, but in other it won't. Evaporation to drive off excess nitric will always work. This might explain the negative stance we usually take to urea.
It's easier to help newbies with easy and proven methods that never fail than adding more chemicals to an unknown mixture.
It is also another chemical to get for the newbie, but evaporation doesn't require any additional chemicals. Another win for the first time user.
Another advantage with evaporation is that it shrinks the volume of the liquid, adding base will increase the volume you need to keep all the salts in solution.

For a professional setting using other chemicals and methods makes sense if you factor in time, space in the lab, throughput and so on... that leads to other choices of methods. Also if you aim for pure gold that goes into alloying or just 99% because your buyer pays on assay and will refine it with other gold in a larger batch will also affect your choices.

Personally I've never used urea, sometimes I use sulfamic acid, sometimes I evaporate. But I try to conserve nitric acid so most times I go straight to precipitate the gold with SMB. The only time I've had problem was when I did evaporate and used water in the final dilution. I had to add HCl and the gold came back in seconds.

I've said it several times before, bur this summer I hope I will get my lab up and running. I got two fume hoods, a place to put them and several fans. If the Covid-19 situation doesn't change drastically I'll also have the time to put everything together. Then I will be able to shoot some videos showing some of the methods we are talking about here.
One fun experiment would be to do a comparison between dropping gold at different pH but everything else the same. I'll put it on the list.

Göran

Thanks Goran. I have the fans and have built the bottom section of my cupboard.

I’ve connected it to a plastic container with a mister fixed to the underside of the lid with an outlet 300mm from the bottom.

I have only needed to add roughly 20ml of base at the most. Having done a fair amount of research, I suspect if the test was done by someone like yourself there would be little to no difference as you would not make the error of excess nitric.

Sulfamic acid I’ve used but the amount you need is not the most economic which is why I was advised to use adblue.

Jmk88 said:

I have seen precipitation of copper, especially when I made the above button as it was from old dirty papers.

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What make you thing the copper contamination was because the button "was from old dirty papers" :?:

I suspect it was the result of raising the Ph with hydroxide :!:

Kurt

Jmk88 said:

Why would I cement everything over days and start over again? That doesn’t make sense when I can use the above method and get nearly pure gold. It’s a waste of time and materials and doesn’t produce you nearly pure gold. You then need to clean, re dissolve, and precipitate which if you aren’t experienced with you’re not going to be able to do the above with excess nitric.

Click to expand...

You are SOOOO wrong about that

I have produced MANY ozt. of gold at no less then 990 & as high as 999 using nothing but copper - from VERY dirty solutions - there is "a bit" of a learning curve to controling the use of the copper - followed by the washing process - of which (the washing process) NEEDS to be done anyway

Copper has been my go to method for MANY years now with AR solutions that are VERY dirty & have LOTS of free nitric in them & can hit 995 - 997 (so near pure) most if not "all" the time

And it does NOT take days - I can go from dirty AR with free nitric - to a poured bar in a day or less

That means drop (with copper) let settle - decant - wash - dry - melt & pour to a (near pure - if not pure) bar in a day or less

Kurt

iron will also start precipitating at the pH range of around 2.5 to pH 4...

Where are you getting this advice?.

Although you may be able to recover your gold from this mess, it is not good advice or practice, when there are much better and easier ways to precipitate gold from the solution...

Note urea is basically useless and will only complicate matters unless you do not overuse nitric in the first place, Urea will only deal with NOx gases in solution, but any free nitric in solution would make urea nitrate which would lead to many other issues or problems, in later steps, including safety.

There is no reason to add hydroxide or some other chemical alkaline like baking soda to raise PH, again you are just making things more complicated.

This is not the way to teach new members how to precipitate gold.
You would be better off teaching them how to recover the gold from that mess using copper.