Oxalic Acid question/questions

[Topher_osAUrus]

Oxalic acid is used for second refining for a beautiful precipitation of gold.

I have scoured the forum for hours, but the only type of oxalic i have seen mentioned are either :
Chemically pure/tech grade
Or savogran wood bleach

The oxalic acid ordered from chemical supply houses is of high percentage and purity (obviously)

Savogran wood bleach is (est)96 percentile in the purity range. With the remainder (according to msds 95-100 *see attached picture) -the msds ingredient list gives me a bit of confusion as to the remainder or the chemical makeup as it states these:
ACGIH/OSHA 1 mg/m3 TWA
ACGIH 2 mg/m3 STEL
Under the oxalic acid, which makes me think that they have nothing to do with the remainder chemical makeup, but just details of the oxalic.

-so what is the other 5 percent, not that it really matters i suppose?

The question.(one of them anyways)
Barkeepers friend -a powder/crystalline cleaner that is in my lab to clean my corningware and lab glass (along with Bon Ami) - it's chemical makeup is(*attached picture 2*):
-oxalic acid 7.5-9.5 percentile
-other constituent compounds are as copied:
-FELDSPAR* Confidential(percent makeup is *confidential*) 68476-25-5
-LINEAR SODIUM DODECYL BENZENE SULFONATE (DDBSA) Confidential 69669-44-9

I believe they are both used as surfactants, but I am probably mistaken.

My questions(finally) are:
-what is the percentage of purity for oxalic acid(in itself) to precipitate gold successfully
-would Barkeepers friend precipitate gold?(i know, use tried and true and dont try to reinvent the wheel..)
-is there a practical way to remove the feldspar and/or ddbsa?
--or would it benefit to leave them, as one is basic, which may make it so ammonium hydroxide could be omitted?
-KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8 is the wiki's composition of feldspar. To me it seems that it would only cause problems in precipitation of gold, especially if its calcium (i just see it reacting with the sulfuric [added for lead removal and crust prevention] making calcium sulfate, which would be a pain to remove from the gorgeous gold.

So.
- Is it worthy of a test?
- should i just make a trip and go to find some savogran wood bleach?
- is there any other *over the counter* wood bleach that works?
--or any other useful product that contains oxalic (with little to no other impurities)

Again, i dont want to reinvent the wheel, i just want to use what i have if possible, but i dont want to make more troubles for myself down the line.
-why go through the trouble of oxalic then? Well, i want to have some gorgeous precipitated gold in a container, just to have for myself and to show others. Yes, i could show them a button, or the brown powder i have in a beaker.. But, most (all) people go "that just looks like mud to me"

And, i want to try to *woo* a couple local jewelers... Which, sadly, none of which can even test accurate purity beyond the scratch test...and even then, they dont use a "comparison" needle..so basically, they know not what they do.

Thanks for any input guys.
Edit to fix a word, and again for grammar
-toph

 

[Anonymous]

Why go through the trouble? Drop with Ferrous Sulphate on recovery drop. Clean the gold up. Process again in AR , then use SMB on your refine drop. Clean again, and job done.

 

[Barren Realms 007]

You can do what Space said to do and have a simple happy life and produce .9995 or better gold every time. Why make things difficult.

Ask him how many times it was suggested to him to do this before he realized how easy and simple it makes things.

 

[Anonymous]

You can do what Space said to do and have a simple happy life and produce .9995 or better gold every time. Why make things difficult.

Ask him how many times it was suggested to him to do this before he realized how easy and simple it makes things.

Ouch Frank! Harsh dude, but very true! 8) 8)

Topher, joking aside Frank does raise a good point. There are often simple ways to get really good pure gold without a lot of fussing around with the more complicated methods. Take the advice - it's both good, and learned the hard way.

Jon

 

[nickvc]

The guys are giving good advice here, I would add to make sure your rinsing is done well on both batches of precipitated gold and have one melting dish for just your high quality gold melts.

 

[kurtak]

Here is from a batch I just did a few days ago (it was actually a few grams more from which I poured the 2) 1 ozt bars)

The original solution was VERY dirty so I recovered by cementing with copper

re-dissolved for the refine drop which was done with ferrous sulfate - I like ferrous sulfate because it seems to give a courser drop that settles better & washes better then an SMB drop

If you look close you can see how it tried to form a pipe even though I poured to a hot mold & kept the flame on it during the pour

An XRF read said it was 100 percent (which of course we know is not "exactly" true)

The only down side the ferrous sulfate is that the solution does not go clear like SMB when the gold is out but rather it (the solution) stays dark --- so you have to be careful you don't over shoot the ferrous sulfate additions (use your stannous)

Proper (complete) washing is really the key to a final clean gold (& not over doing your precipitant in the first place)

Kurt

 

[Topher_osAUrus]

I know, i know.. Lol

-you guys...

Kurt, your gold is beautiful.

Jon, barren, anyone else.
-i just wanted to have some nice pretty *shiny* precipitated gold that i could have in a small vial to show... As the light brown mud people just think is dirt.

And, i want to see the reaction first hand for oxalic precipitation.

But, I was just "testing the waters" to see if there was any of you whom (who?...whom..whatever.) have used oxalic acid of lower percent or purity. And what acceptable impurities could there be.

I use ferrous sulfate for my first ppt, and sodium metabisulfite for my second.
I havent done a second precipitation in awhile, because i am one of the guys who only deals with a few grams at a time, and i am wanting to do one big drop, clean, melt.

As doing it gram by gram is increasing loss and cost from chemical usage and electricity.

Thank you guys for the replies

 

[Anonymous]

Hey Kurt

What problems do you experience if you put too much Ferrous Sulphate in?

 

[Topher_osAUrus]

Iron contamination i believe Jon.

Cured easily with the HCl wash procedure.

 

[Anonymous]

I ask because I never weigh or check additions of Ferrous Sulphate. I just add it unless I have a negative Stannous test but then again it's entirely likely that I often put in too much. How would there be an iron contamination in the powder though? Yes the liquid will have some by definition however I'm not sure where it would come from otherwise.

 

[kurtak]

As a side note --- I have turned out some right nice gold (not "perfect" - but nice) going right from cementing with copper to melting :shock:

I know this is not the excepted norm - just saying it can be done

if your solution is "relatively" clean to start with (meaning not horrible dirty but not exactly clean ether) cementing with copper can get you in the range of 99 plus (at least based on an XRF read out)

There are a few tricks to it & a required piece of equipment

The first trick is using copper "powder" (I use 300 mesh copper)

The required piece of equipment is a stirrer hot plate --- you want the solution to be on the hot side of warm & the stirrer turned on a speed that will keep the copper in suspension when you add it - as well as keeping the gold in suspension as it cements out

You want to add your copper powder is small increments - no more then a gram - gram & a half to start with (or you may get a foam over --- eave "plenty" of head room in your beaker)

let each copper addition stir for about 5 - 7 minutes to insure all the copper gets dissolved

as you near the end start cutting back on your copper additions & increase your stir time to about 7 - 10 minutes --- if your gold starts to pile up on the bottom out side edges of the beaker reach in with a glass stir rod & give it an assisting stir to bring it up into the solution for a bit ( the key here being you want to be sure the copper stays up in the solution long enough to fully dissolve & not end up getting trapped in the gold powder)

As you near the end your copper addition are reduced to just pinches (good old stannous testing) & you want to stop "just short" of a complete drop (just a hint of gold showing on your stannous test)

let your last copper addition stir for about 15 minutes (20 minutes wont hurt) assisting every now & then with a glass rod stir (if need be)

let settle - decant - water wash --- send the decant & water wash to the stock pot (remember - you stopped the copper addition just shy of complete)

Now do your HCL wash & final water wash --- dry & go to melt

When you do your melt - hit the molten gold with a pinch of potassium nitrate

Now ask me why I would employ this method rather then the "normal" method of doing a recovery drop - re-dissolve & then another refine drop --- & I will be glad to explain that to :mrgreen: (tomorrow)

Kurt

 

[Anonymous]

Thanks Kurt

One thing though- what if your solution has other PMs and PGMs in it? The copper is going to bring those down as well.

 

[kurtak]

Hey Kurt

What problems do you experience if you put too much Ferrous Sulphate in?

My only point was that because when using ferrous sulfate the solution does not start shifting to a more clear solution as it nears the end of the gold drop like SMB does (which is somewhat of an indicator when using SMB)

Rather - because the solution stays dark when using ferrous sulfate - its harder to tell your reaching the end - so stannous testing is more important if your using ferrous sulfate

I just wanted those that have never used ferrous sulfate to be aware that unlike SMB the solution does NOT shift to a clear solution - don't keep throwing ferrous sulfate at it expecting a shift to clear --- use your stannous :!:

Kurt

 

[nickvc]

You tend to get iron contamination if the ferrous has gone off colour from that nice emerald green colour to brown, adding it by dissolving in hot water and adding a touch of HCl and then pouring just the liquid ferrous also helps, good rinsing of the precipitated gold are as in most precipitations a must for high quality.

 

[Anonymous]

My only point was that because when using ferrous sulfate the solution does not start shifting to a more clear solution as it nears the end of the gold drop like SMB does (which is somewhat of an indicator when using SMB)

Rather - because the solution stays dark when using ferrous sulfate - its harder to tell your reaching the end - so stannous testing is more important if your using ferrous sulfate

I just wanted those that have never used ferrous sulfate to be aware that unlike SMB the solution does NOT shift to a clear solution - don't keep throwing ferrous sulfate at it expecting a shift to clear --- use your stannous :!:

Kurt

Kurt if you are doing a recovery drop from a really dirty copper/contaminant rich solution from something like ceramic processors then adding SMB doesn't turn it clear if you're talking about 3 litres with 30g plus of gold. I must admit that, the point of turning clear (when it happens) then drags down all the copper anyway in one fell swoop.If I am going for a true refine as opposed to a recovery drop then I don't go that far in the first instance. The first part of the drops are extremely pure and I decant off the remainder of the solution before blasting it with SMB because regardless of what people claim here you CANNOT clean darker gold drops to the same purity as the first drops, so why mix them? I separate them out.

Pure gold is a really pale colour. It almost looks leached of colour. Try what I have said here and separate the drops and then try to clean the last part of the drop to the same colour as the first part. You won't be able to.