# PMG precipitation Help Please



## NoIdea (Aug 30, 2011)

Evening All – Browsing through the internet looking for HCl/Cl digestion as a search, found what I was looking for, right here in the forum. :roll: 

I have searched the forum for any mention of Gold-N-Scrap, no show.

Got a question regarding palladium recover from AR posted on this site, please?

http://www.goldnscrap.com/index.php...rial&catid=40:platinum-group-metals&Itemid=52

Here they use concentrated solutions for the precipitation of PMG’s, which is different to this forum suggested methods, not that I’m complaining, on the contrary, I am quite happy, more than happy, with the this forums methods, and have no plans on changing.

My question is why do you think they do their work with concentrated solution? 

And will they achieve full recovery this way?

Thanks and Cheers

Deano


----------



## rusty (Aug 30, 2011)

NoIdea said:


> Evening All – Browsing through the internet looking for HCl/Cl digestion as a search, found what I was looking for, right here in the forum. :roll:
> 
> I have searched the forum for any mention of Gold-N-Scrap, no show.
> 
> ...



Sam from Gold n Scrap is a well noted forum member.

From all the books and instructions I've read or been given, you work from concentrated solutions when precipitating platinum group salts. Even then full recovery is limited your stannous will almost always test positive for traces remaining. These traces go into the stock pot to accumulate into a more concentrated soloution where they can be recovered more effectively.

This is why the stock pot becomes an important accessory in the lab, it is akin to the worlds oceans the cess pools of the world.

Regards
Rsuty


----------



## Palladium (Aug 30, 2011)

http://goldrefiningforum.com/phpBB3/memberlist.php?mode=viewprofile&u=9049


----------



## samuel-a (Aug 30, 2011)

rusty said:


> From all the books and instructions I've read or been given, you work from concentrated solutions when precipitating platinum group salts. Even then full recovery is limited your stannous will almost always test positive for traces remaining. These traces go into the stock pot to accumulate into a more concentrated soloution where they can be recovered more effectively.
> 
> This is why the stock pot becomes an important accessory in the lab, it is akin to the worlds oceans the cess pools of the world.



I could not have said it better, rusty. Thank you.

NoIdea, where on the forum had you seen a suggestion to dilute PGM's solutions before precipitation?
C.M. Hoke took note for the reader to distinguish his PGM's solution which needs to be as concentrated as possible from the Gold bearing ones that should be diluted to some extant.


p.s. - What is the current process you are using?


----------



## goldenchild (Aug 30, 2011)

NoIdea said:


> My question is why do you think they do their work with concentrated solution?
> 
> And will they achieve full recovery this way?



Pt and Pd salts dissolve in plain H20 so keeping your solutions concentrated is a must. I'd imagine if your solutions were diluted enough your salts would very quickly dissolve right back into solution or not ppt at all.

Full recovery? Maybe. I'd think you would have to work pretty fast to get the salts out of solution. Even when first dropping with zinc to get the PMGs out in metallic form the metals tend to redissolve into solution.


----------



## NoIdea (Aug 30, 2011)

Morning All – Typical, when I want to find something, I can’t.

Here is an abstract from Hoke describing the dilution I referred to, dilution x10, others I’ve read say dilute 3x. 

Hokeage172. When all the gold is dissolved, place the solution in an evaporating dish and expel nitric acid, as usual, taking up the syrup in hydrochloric acid, and evaporating again, as usual. When you are sure all the brown fumes have been expelled, add considerable water say *ten volumes or *more and set aside for several days to settle..... You are now ready to precipitate the gold again.

I guess I need clarification as to what is referred to as dilute and concentrate. To me the word dilute immediately cancels out concentrate. Or when adding water, their must be a line between concentrate and dilute.

Thanks

Dean


----------



## Palladium (Aug 30, 2011)

Those are two different materials you are making reference to. The first was palladium which needs to be concentrated and now gold which needs to be diluted for a better drop. She is talking about gold and not pgm’s in that paragraph.


----------



## goldenchild (Aug 30, 2011)

I only dilute my gold solutions with as much water as is used to clean the filters and vessels. But I also don't evaporate down to the consistancy of syrup. So if you're talking gold I would say dilute to 3x. If you're talking PMG then concentrate.


----------



## NoIdea (Aug 30, 2011)

Thank You Very Much, penny dropped. 

Kind of like mixing metaphors but on a liquid scale. :lol: 

I was dropping gold from dilute solution using ferrous sulfate, leaving over nite, decant/filtering to remove black precipitate, then adding ammonium chloride to drop Palladium, I did get, what looks like a white-ish precipitate, which could be salts or Palladium, I have yet to filter, decided to read a bit more, hence my question.

I am taking my time, using small amounts of solution, need to get it right first before going BIG. I have about 500g of, mostly, base removed; incinerated ash soaking in HCl/Cl, I'm using trichloroisocyanuric acid as my chlorine source. Breaking the trichloroisocyanuric acid into small bits, soaking in a water solution for a week or so will give a very strong chlorine solution, very yellow, needs to be kept in a sealed container. An old bleach bottle is perfect.

http://en.wikipedia.org/wiki/Trichloroisocyanuric_acid

Again Thanks

Deano


----------



## Geo (Aug 30, 2011)

you cant really soak in hcl+cl. as the hypocglorite goes into the acidic solution it will digest and release chlorine gas. this gas will "gas off" fairly quickly. your only dissolving gold as long as chlorine gas is present. it may still smell like chlorine bleach for quite some time but the reaction stops soon after you add the bleach.


----------



## goldenchild (Aug 30, 2011)

Deano,

Ammonium chloride is to drop Pt. Sodium chlorate is to drop Pd but no matter. As stated before a dilute solution will dissolve your salts back into solution. I think you would find it easier to drop your gold and then cement out your PGMs with copper. You could then take your PGMs and redissolve them in a concentrated AR solution. THEN drop salts.


----------



## rusty (Aug 30, 2011)

goldenchild said:


> Deano,
> 
> Ammonium chloride is to drop Pt. Sodium chlorate is to drop Pd but no matter. As stated before a dilute solution will dissolve your salts back into solution. I think you would find it easier to drop your gold and then cement out your PGMs with copper. You could then take your PGMs and redissolve them in a concentrated AR solution. THEN drop salts.



Ammonium Chloride is fairly passive, Sodium Chlorate on the other hand should be added to your heated solutions in very small additions.

My sodium chlorate is a year old, it did not react, I added more - same thing. Dug down into the canister grabbing some sodium chlorate from near the bottom whoa different story. Lucky I had an empty vessel nearby to pour off half the foaming liquid or it would have foamed over spilling hard earned money.

Purchase only the amount your going to use in a short time, sodium chlorate does go stale. My ammonium chloride on the other hand is still as fresh the day I purchased it almost a year and a half ago.

Just a reminder keep sodium chlorate away from organic material, it could bust into flame.

Regards
Rusty


----------



## Geo (Aug 30, 2011)

@ NoIdea
"I am taking my time, using small amounts of solution, need to get it right first before going BIG. I have about 500g of, mostly, base removed; incinerated ash soaking in HCl/Cl, I'm using trichloroisocyanuric acid as my chlorine source. Breaking the trichloroisocyanuric acid into small bits, soaking in a water solution for a week or so will give a very strong chlorine solution, very yellow, needs to be kept in a sealed container. An old bleach bottle is perfect."
i have never used this process before. if you have time later, can you PM me and give me some details on this as its something i would be interested in? thanks


----------



## NoIdea (Aug 31, 2011)

Thanks for the heads up Rusty, I’ll be using potassium chlorate as a substitute, and I am well informed regarding the dangers of the chemicals I use, if I’m not then I’ll look it up.

Geo, I am still experimenting the hard way as I am committed, or should be. I am using a sealed unit, so unless the chlorine is leaking out, then with the odd shake shake shake, the chlorine smell, when un-sealing the unit so as add more trichloroisocyanuric acid solution, is gone. I will assume that when there is a smell after time, i.e. the chlorine is not being consumed, that the reaction is complete or near completion, not sure how you can tell with an open or semi-open reaction vessel.

Thanks for correcting me on what drops what, I do tend to mix things up on the odd occasion or two.

Thanks

Deano


----------



## Palladium (Aug 31, 2011)

Here's something you might find interesting. The info is no longer available on the web, but you might find something in there to peak your interest.

http://web.archive.org/web/20080115234543/http://www.chlorine-generator.com/Process.html


----------



## NoIdea (Aug 31, 2011)

Thanks Palladium, it's between 7 and 15deg C here at the moment, so that's gotta help as well as being a sealed unit, summer is going to be a whole new ball game. 

However, summer is the time I do alot of evapourating, nice and hot, plenty of wind.  

Pro's and con's for everything I guess. :roll: 

Any idea as to chlorine and gold reaction vs. temperature, in aqueous or gas?

Again, Thanks

Deano


----------



## Palladium (Aug 31, 2011)

This might help. Their is a chart in there for comparison of dissolution rates.
It also cites references to patents from which the chart was comprised.


----------



## NoIdea (Aug 31, 2011)

Thanks Palladium - Awsume read, brought up more questions than answers. :lol: 

Hmmm back to the books and a little bit of experimenting. :mrgreen: 

Again Thanks


----------



## freechemist (Aug 31, 2011)

In a significant number of posts around PGM-precipitation, questions of solution-concentrations arise. Therefor I think, it has first to be defined, what the meaning of "concentrated" and "diluted" in a more precisely formulated manner is. After my experience, this definition is process-dependent and best formulated as a concentration-range, based for example on grams of metal to be treated/precipitated per liter of solution. Thus here a few rules of thumb for different procedures:
1) dissolution of high PM-containing alloys (i.e. from dental scrap with PGM's and base metals, PM-content at least 60%): 75 - 100 g total metal per liter in final solution.
2) Au/Pt/Pd-solutions from dental scrap: ca. 50 g total metal / liter for Au- precipitation, and for Pt/Pd-precipitation, if Pt and Pd are precipitated first, like mentioned in one of Harold's posts.
3) Pt/Pd-solutions: 25 - 50 g total metal / liter for Pt and/or Pd-precipitation. 
4) Diluted Pt/Pd-solutions, after separation of main PM-constituents: 1 - 5 (max) g total metal / liter for cementation. 

freechemist


----------



## goldenchild (Aug 31, 2011)

rusty said:


> Ammonium Chloride is fairly passive, Sodium Chlorate on the other hand should be added to your heated solutions in very small additions.
> 
> My sodium chlorate is a year old, it did not react, I added more - same thing. Dug down into the canister grabbing some sodium chlorate from near the bottom whoa different story. Lucky I had an empty vessel nearby to pour off half the foaming liquid or it would have foamed over spilling hard earned money.





NoIdea said:


> Thanks for the heads up Rusty, I’ll be using potassium chlorate as a substitute, and I am well informed regarding the dangers of the chemicals I use, if I’m not then I’ll look it up.



Truth be told there is a much easier way to get your Pd out of solution than using sodium chlorate. You can use it if you are in a pinch or may choose to use it on a regular basis. Regular old clorox will drop Pd salt out of solution and in a hurry. It's just like adding smb to HAuCl4. The ppt is also quite thorough if you've made sure to concentrate your Pd bearing solution. As an added bonus the reaction is not very violent so foam overs shouldn't be an issue. You're skipping a reaction and adding sodium hypoclorite right off top.


----------



## Joeforbes (Sep 1, 2011)

goldenchild said:


> Deano,
> 
> Ammonium chloride is to drop Pt. Sodium chlorate is to drop Pd but no matter. As stated before a dilute solution will dissolve your salts back into solution. I think you would find it easier to drop your gold and then cement out your PGMs with copper. You could then take your PGMs and redissolve them in a concentrated AR solution. THEN drop salts.



"In the presence of 1M NH4Cl, (ammonium hexachloroplatinate's) solubility is only 0.0028 g /100 mL."

Source: http://en.wikipedia.org/wiki/Ammonium_hexachloroplatinate

Is the liquid dissolving the values really the issue, or is the reaction itself less effective when dilute? It would take 10,000 ML of 1M NH4Cl solution to dissolve .28g of [NH4]2[PtCl6].


----------

