# Nitric and Palladium



## xsspirito (Sep 22, 2011)

Hello guys (and gals), 

Dose anyone know how much Palladium would be dissolved in Nitric acid at room temperature before all copper is digested? 
Lets say ... I have 100g of material of which 2.5% is Palladium, 2% Gold 0.5% Platinum, 8.5% Silver, 0.8 Nickel and 85.7% Copper, it will take 2-3 hours for nitric to dissolve all the silver and copper, during this time how much of my Palladium would be dissolved in Nitric? I know it dissolves slowly but how slow? 

Thank you!


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## samuel-a (Sep 22, 2011)

Maybe i'm mistaken... 
but i think it is next impossible to pre determine what you seek for...

On different matter, did you ever consider rasing the Cu content to >95% and simply part it electrochemically?
This way you would be left with slimes containing mostly PM's with very little Cu contaminate... sure will save you on acids...


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## shadybear (Sep 22, 2011)

Or couldnt you remove the copper with HCL


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## xsspirito (Sep 22, 2011)

Thanks for reply, guys. 

Samuel, I can not do it electrochemically as it's in a powdered state contaminated with glass, I could dissolve all in Aqua Regis and then use Zinc (or hydrazine, which is expensive but would drop more metal) to drop all metals, but ... I have 1.25 tons of this ... and not sure which will be the cost effective way of doing it. Glass contamination is about 68% plus some 2-3% polymer, which I will vaporize and distill. 

shadybear, To dissolve it in HCL I will have to add Hydrogen Peroxide, what will produce small bubbles of Chlorine and form Auric Chloride (am I right?).


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## Geo (Sep 22, 2011)

hcl acid alone will not dissolve gold or copper. add the material in question to hcl acid in a chamber big enough to hold the volume of material and chemicals with 1/4 of available space left. add H2O2 (peroxide) to the mix of a ratio of 1 US cup to 1 US gallon to start the reaction. it will immediately turn yellow then quickly turn green. add a source of oxygen such as an air supply in the form of a bubbler, if you are doing batches in a plastic drum you may need to use several, maybe 4 if your volume of chemicals is 30 gallons or more. set the air bubbling and leave it alone for 4-5 days, if the copper is bare copper as in particulate form it will go much faster. this will put the copper and tin in solution without effecting the PM's. after the solution turns brown to brown/black dip or siphon liquid down to the powders in the bottom and you have successfully removed the copper and tin from your material.


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## xsspirito (Sep 22, 2011)

What if I get rid of polymers and melt the glass and metal ? 
What will I end up with? 
Any toughs? 

OK... I'm going to try that tomorrow in the lab  

P.S. The thing is I have 400kg of copper and not sure the best action here, if it was an alloy the best option was electrolysis.


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## goldsilverpro (Sep 22, 2011)

xsspirito said:


> What if I get rid of polymers and melt the glass and metal ?
> What will I end up with?
> Any toughs?
> 
> ...



If I understood you correctly, by using the present PM prices (which are dropping rapidly), I came up with these approx. dollar values: Pd-$177K; Au-$378; Pt-$93K; Ag-$33K; Cu=643#. Not including the Cu (which I wouldn't worry about), that's a total of about $681,000, if I did the math right. If this were mine, I would do a lot of experimentation to find the best and most efficient method, changing only one variable at a time. I would also want to own an AA (for the liquids) and fire assay setup (for the solids and maybe the liquids) to track the metals through the experiments and the process.

These ideas are just that, ideas. They may or may not work. They look good on paper but, when actually doing it, things crop up that you hadn't considered. However, you have to start somewhere. I'm sure there are other possible ways. Maybe, Lou, Harold, 4metals, and others can chime in.

Eliminating the organics and then melting was also my first thought. If you can make it work, that would certainly be the cleanest way to go. Ideally, you would end up with assayable bars containing all the metals, which you could either deal to a large refiner or process yourself (let's deal with that later), plus a lot of slag which could easily hang up BBs of metal unless you could thin it properly (maybe, fluorspar). The melting point of most glasses is quite high, but the melting point of many can be lowered (to maybe 1000C) by the addition of definite quantities of sodium carbonate. At this temperature, you could use a gas furnace. If the slag is thin enough, most all of the BBs will settle by casting into a large size, pre-heated, cast iron, cone mold, if you can keep the slag molten long enough. I have also heard of people casting into a large cone-shaped depression formed in pre-heated casting sand. That would keep everything molten for a long time.

If all the individual metals, glass, etc., are in separate particles, and the metals are not alloyed or bound up with the glass, you could leach out all the Pd, Ag, and Cu with nitric. For the whole lot, I estimate it would take about 600 gallons (11-12 drums) of 70% nitric cut 50/50 with distilled water and heated. You could use a non-magnetic stainless tank for the nitric. After this, I would use a huge vacuum filter and rinse well. Then, leach the Au and Pt with either aqua regia or HCl/strong H2O2. The latter might be best since you wouldn't have to deal with the elimination of excess nitric before dropping the metals. Besides being able to rinse all the values in solution from all of that glass, the biggest problems I see are dropping the Pd from the nitric solution and all of that dissolved copper present. Any excess of nitric will have to removed first. Therefore, try to use only a slight excess of nitric, no matter how slow it goes. To me, the simplest way to remove an excess of nitric is to use sulfamic acid.

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=51&t=10799&p=105096&hilit=sulfamic+acid#p105096

You could probably leach everything but the silver with aqua regia or HCl/H2O2 (possibly best), and then go after the silver with nitric. However, depending on the particle size, a certain portion of the silver could be converted to silver chloride. This wouldn't dissolve in the nitric and would possibly be lost, since leaching out AgCl with ammonia, sodium cyanide, or sodium thiosulfate would be a bear.


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## samuel-a (Sep 22, 2011)

What a great post Chris.

Though, i'm still in the opinion that he will benefit from melting and parting in a cell, even with the high silica content.
As GSP suggested, there are ways around that such as soda ash + fluorspar...

If it were me, i'd probably out source the smelting process to a professional smelter and ask 50-100 kilos anodes + all of the slag back (which will need to be assayed).


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## xsspirito (Sep 23, 2011)

GoldSilverPro, Thank you for detailed reply.

Your math is right  I was thinking of £400,000, and of course TESTING, I would say a lot of testing.
I have already tested a batch, chemically dissolved and recovered all metals including traces of the nickel.
I have a full lab so I can do lots of experiments.

First will try to melt with induction furnace, it's 30L (8 Gallons) so if successful will take me about 50 loads. Ideally it should work as 30% of the mass is metal. If it wont work will have to find a gas furnace. BUT! Some oxides, sulfates and metals mix in with glass, it might be a problem, not sure but ... 

Will let you know tomorrow. ITS COOKING


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## 4metals (Sep 23, 2011)

Considering the high percentage metals in the material I would definitely start with melting. A good flux for this type of material can be made as follows;

15% Kryolite
35% Borax (anhydrous)
25% sodium nitrate
12 1/2% soda ash
12 1/2% slaked lime

This flux has served me well melting high yield ceramic substrates and there was only a minimal hold up in the slags which can be crushed and shipped as a low grade sweep to a copper smelter. Considering the high percentage of metal this flux can be mixed as 1 part flux to 3 parts of the glass metal mixture and you should get a nice thin slag for easy pouring. If it is not a fluid slag, slowly increase the flux proportions but you shouldn't have to go over 35% by volume flux. 

The kryolite, which is sodium hexaflouroaluminate will perform as the the flourospar in GSP's suggestion to thin the flux and minimize the bead hang up. 

I would pour these melts into a cone mold and closely examine the glass slag which should be a black color and free of beads with the right proportions. Once you come up with the right flux to material mix, assay the bar to determine the copper percentage and upgrade the copper content to make this a copper plating cell with very happy slimes.

My second choice would be the acid leach but unless you are in a well equipped and exhausted refinery, the fumes may be a bit much. Plus without good rinsing and vacuum filtration, the glass particles (depending on their shape and surface finish) may trap more values than you are willing to lose.


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## goldenchild (Sep 23, 2011)

Would you be willing to sell small quanties of your material to come up with an answer? Say 0.5 - 1 pound samples?


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## xsspirito (Sep 24, 2011)

OK guys, BAD news.

I melted it, and ended up with a very strange material, first of all glass turned greenish blackish brownish mass (or mess).
I added Borax, sodium nitrate, soda ash to bring the melting temperature down, it melted at 1240 C.

1. It should not have turned green, this indicates presence of tin oxide? Wen I refined a small batch first time, I boiled it first with Hydrochloric acid, and did not test for tin, further more the vacuum tubes did not have any solder on them.
2. I managed to get some metal to settle on the bottom about 20-22% of it, the rest is suspended in the mess (bead hang up).
3. I tried at range of temperature, the higher it got, the darker became the mass. I even boiled it which made a bigger mess out of it.
4. After it solidified I pulverized it, used a strong magnet to separate metals (I have a little nickel in the metal), ended up 15% short of what it was supposed to be.

Solution 1: I have access to atmospheric polymer distillation reactor (made from wolfram alloy), I can have the temperature increased from 700C to 2750C. WHAT IF I try to vaporise some of the materials and then distill it? The reactor has 3 distillation chambers at different temperatures. I know it sounds funny.

Solution 2: Do you think I can use a conductive polymer paste to bond the material and then try to clean it electrochemically, as suggested by Samuel? 

Solution 3: Good old chemical leaching method. 

P.S. I will try method suggested by 4metals today and post the results. 

BTW how can I test the chemical composition of the galls I have? It might be some sort of an exotic glass. Will atomic absorption spectrophotometer work on glass?


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## 4metals (Sep 24, 2011)

The glass has to be crushed into a fine powder and fused in a litharge based flux and the resultant lead is cupelled, resulting in a dore bead containing total precious metals. That bead can be digested and fire assayed.


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## samuel-a (Sep 24, 2011)

xsspirito said:


> Solution 2: Do you think I can *use a conductive polymer paste to bond the material* and then try to clean it electrochemically, as suggested by Samuel?



That was not my suggestion.

To part your material electrochemically, it depent on you melting your metals successfully and evenly.

Follow 4metals flux recipe and tweak it as needed. I also hope you will give it enough time to pool at the bottom.


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## Lou (Sep 24, 2011)

Want to sell it?


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## xsspirito (Sep 25, 2011)

Sorry guys, I can't sell it.


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## butcher (Sep 28, 2011)

Just thinking about this.

Is this from vacuum tubes?
Could you look at this similar to mining, what size particles are the metal? If product was crushed fine would glass be smaller powder than metal, and maybe screened from metal (or majority of metal, or could metals be reduced in size (if already almost smaller than glass) with acids (not necessarily completely dissolved) and screened from glass?

Or 

Could both be powdered and panned (shaker table or other mining method), glass would be lighter. Even if you did not get complete separation it may save acids, or fuel for furnace, and could limit waste generated.


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## freechemist (Sep 30, 2011)

Hello xsspirito,

Having read through all posts covering your problem, I stumbled over goldsilverpros answer, in which he makes a rough estimation about values in the material and quantities of nitric acid required, to leach out Pd, Ag and Cu, provided that all the individual metals, glass, etc., are in separate particles, and the metals are not alloyed or bound up with the glass. Under the same propositions the entire metal values, Cu, Au, Pt, Pd, exempt silver, could be leached out with a HCl/HNO3-mix, suspending the material to be treated in HCl, diluted with water, heating to ca. 80oC-90oC, and slowly adding HNO3 as oxidizer in such a manner, that reaction never becomes too violent. Thus, calculating the quantities of 32% HCl, 65% HNO3 and water, I came upon the following total numbers: 1'740 liters of 32% HCl, diluted with 870 liters water, and 470 liters of 65% HNO3 to oxidize all metals. Ideally you end up with a solution of Au, Pt, Pd and, of course the total Cu, and a residue consisting of glass- and polymer particles, together with some AgCl and undissolved metallic Ag. The filtered solution will contain maximally up to 3 g Au/liter, 0.7 g Pt/liter, 4 g Pd/liter. In place of cementing, this solution could be treated with a strongly basic anion-exchange resin in chloride-form, like Amberlite IRA-410, produced by Rohm & Haas, which in bulk-quantities probably will cost you about 20 - 30 $ per kg. This resin will absorb Au, Pt, Pd from the filtered solution as complex anions AuCl4(-), PtCl6(2-), PdCl4(2-) (and PdCl6(2-), eventually). The resin can be loaded with up to 10% of it's dry weight with precious metal-anions, leaving the copper (and also nickel) untouched, in a solution containg ca. 1 to
only a few milligrams precious metal in 1 liter. Thus, assuming a total of roughly 20 kg Au+Pt+Pd a minimum of about 200 kg of resin (4'000 to 6'000 $) are required for nearly quantitative absorption of total pm-values. After, the loaden resin can be carefully burned down and calcined (end: 800oC to 900oC) to a finely divided, essentially metallic residue.
An alternative approach, to work up the material would be, to dissolve the glass particles in hot concentrated aqueous NaOH under pressure at 150oC to 200oC, calculating the weight of glass as SiO2 (quartz), like ordinary water-glass is produced by dissolution of quartz at high temperature and high pressure. On filtering, the silicate solution is separated from metal- and probably polymer-particles, and this residue could be burnt, melted and further treated by known methods. Even another alternative is the dissolution of glass in an excess of hydrofluoric acid, producing a solution of H2SiF6, Na2SiF6 (and excess HF), from which metal and polymer particles can be separated by filtration.

Of course, like goldsilverpro stated in his post, all these suggestions mostly are just ideas, exempt the resin-treatment of precious-metal-solutions in presence of high copper-concentrations.

Good luck and regards, freechemist


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## Anonymous (Sep 30, 2011)

4metals said:


> This flux has served me well melting high yield ceramic substrates


Can you elaborate? Do you mean crushed/ground substrate?Or in cpu form.I am looking for a more thorough method for extraction from crushed substrate,as opposed to thio.The fine powder is a huge pain when using thio on ground substrate.


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## 4metals (Sep 30, 2011)

Back in the day, I melted ceramic hybrid circuits (thick film ) whole with this flux mixture. The melt often stayed in the furnace for 8 hours to liqueify the substrates. Copper was used as a collector and the bars were electrolytically refined in a copper sulfate cell, the anode slimes is what we were after.

Considering the high copper in the material described in this thread, minimal or no copper would need to be added, that is why I would choose melting first.


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## Dr. Poe (Oct 23, 2011)

Nitric acid reacts differently according to it's dilution. Pure nitric acid doesn't dissolve copper! The nitric acid must be "cured"to include nitrous acid which is formed very slowly at first in contact with copper. As the acid becomes red with NO, the action increases. Dilution with pure water (rain or distilled) ; that is adding nitric acid to water and never the opposite to reach a 1:1 ratio, and then curing the acid by adding a small sliver of copper or by exposing the acid to sun light will activate the corrosive action. 1:1 is still considered very strong acid. If heated, all but gold and the heavy pgm's will dissolve. If boiled, a golden powder will precipitate with the gold that is the basic oxide of palladium. This oxide of palladium will dissolve in diluted HNO3 or in water, but not in concentrated HNO3. So now some of you must have surmised that the yellow gold that seemed to disappear when washed with water was actually palladium.


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## Oz (Nov 13, 2011)

This is why members should know testing and always test washes and waste solutions.


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## rcarbon (Nov 10, 2013)

About 4 months back, I tried to dissolve about 10 gms Pd in 50 ml HNO3, but the reaction did'nt started, I tried again with 1 gm Pd in 50 ml acid, the reaction started and in about 1 hour , 1 gm was completely dissolved, to this I added 2 more gms, It also dissolved in 1 hour, I put 5 gms, again it dissolved completely, to my surprise, this way I manage to dissolve almost 28 gms Pd in just 50 ml acid.

And now again I am trying again but unable to dissolve even 10 gms in 50 ml acid. Yes 4 months back it was summer time in Canada with lot of sunlight but not now.

I will appreciate if someone can explain what all is happening in above process.


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## butcher (Nov 10, 2013)

What state is this palladium in?
palladium oxide is acid resistant.


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## rcarbon (Nov 10, 2013)

Palladium is in pure metal grain form. 4 months back and now, i bought it from same supplier.
I think, 4 months back,in summer time, very heavy sunlight accelerated this reaction, which is not happening now. But I dont know the exact reason. remaining all conditions are same, same is the conc. of Nitric acid.


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## butcher (Nov 10, 2013)

I am not sure what concentration of nitric you are using.
Nitric when dilute will normally dissolve metals easier than a concentrated solution.
I think there are several reasons for this, too strong it can oxidize a metal into a passivated state, forming an oxide coating hard to dissolve or to remove for further acid attack of metal, and also NOx gases in the dilute nitric acid are actually needed to do most of the work of dissolving metals, dilute nitric not only will have more of these gases of decomposed NOx (than more pure fuming nitric acid would), water helps to keep the NOx gases into solution to do more work, and water can act as a solvent for the metal nitrate solutions as the metal dissolves, as far as the sunlight is involved, can only think of a couple of explanations sunlight will decompose HNO3 (forming more of these NOx gases in solution, and also provide some heat which also can help the process.


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## rcarbon (Nov 10, 2013)

butcher said:


> I am not sure what concentration of nitric you are using.
> Nitric when dilute will normally dissolve metals easier than a concentrated solution.
> I think there are several reasons for this, too strong it can oxidize a metal into a passivated state, forming an oxide coating hard to dissolve or to remove for further acid attack of metal, and also NOx gases in the dilute nitric acid are actually needed to do most of the work of dissolving metals, dilute nitric not only will have more of these gases of decomposed NOx (than more pure fuming nitric acid would), water helps to keep the NOx gases into solution to do more work, and water can act as a solvent for the metal nitrate solutions as the metal dissolves, as far as the sunlight is involved, can only think of a couple of explanations sunlight will decompose HNO3 (forming more of these NOx gases in solution, and also provide some heat which also can help the process.



yes you are right, now I have seen that yes Pd grains become passivated after some time. Earlier also and now also I am using 68% nitric acid.

My aim is to get Palladium nitrate with minimum free acid. What i did earlier was, I , took 50 ml acid and started putting in Pd grains, increment of 5 gms, spread over 24 hours time. after about 16 hours, i could see very thick paste of Pd Nitrate along with lots of undissolved Pd grains. To this I added about 40 ml more DI water, and in almost next 1 hours every thing was dissolved , so now I had 28 gms Pd dissolved in just 50 ml Nitric.. This process emitted very little fumes. 

Now also I am repeating the exactly the same, but now this process emit large amount of fumes and after some time metal becomes passivated. 

Now also I can get 28 gms of Pd Nitrate, but it will be in about 100 ml of acid, and amount of free acid will be too high. Now if I boil off this free acid, I can see formation of extremely fine black color soot at the bottom of solution.

Please suggest what to do to make Pd Nitrate with minimum free acid


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## rcarbon (Nov 10, 2013)

This time I also tried to remove oxide layer from grains, by first taking out undissolved grains washing them with water several time, drying them completely , then immersing them in HCl for 5 min, again water washing them and drying them completely. On putting them in old Nitrate solution, reaction starts vigorously and very soon they become passivated again.


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## butcher (Nov 10, 2013)

I have rarely worked with Palladium, and am more familiar with the reactions of silver.

Lets look at dissolving silver.
Too concentrated of an acid will actually slow the process. 
Even in more dilute acid, there can be a delayed reaction.
What I believe happens is the silver first passivates with an oxide layer as the silver is oxidized by the nitric, at the same time some of the nitric in solution begins to form NOx gases, It is these NOx gases in solution, from the decomposition of nitric that help attack and are what combine with silver to make silver nitrate as the nitric is reduced (by oxidation of the silver) to nitrates, after this delayed reaction, the reaction becomes more violent, somewhat I believe from the heat produced, but also from the decomposition of the nitric acid itself, silver oxide layers are dissolved faster by the production of more of these gases, and there is so much of these gases in solutions oxidizing and themselves reducing with the silver the silver no longer is in a state of passivisation but is quickly being dissolved into the solution with the help of the water.

Note here also water can help to keep quite a bit of these gases in solution NO2 in this water can convert back to HNO3 instead of leaving as a red brown cloud of wasted nitric acid and gas that had the possibility to do more work, Note sometimes I add a bit of H2O2 with the water, this can help to provide oxygen in solution, so that NO gas can form NO2 in solution with the water (the idea is help the nitric go further keeping these gases in solution and working on the silver.

After most of the nitric is consumed in this violent reaction, the reaction will slow to a crawl, although there is still quite a bit of free nitric acid in solution, this may be because the heat of the reaction is not as strong, or for some other reason it slows to a crawl, heating the solution at this point will dissolve more silver into solution the heat helps the reaction proceed faster, heat makes the acid in this silver salt solution stronger, and heating can drive off water as the reaction continues helping to concentrate the nitric left, I find I can put an awful lot more silver into solution in this latter process using heat.

Most of the time we recommend diluting your 70% HNO3 with equal volumes of water, nitric is expensive for me and hard to obtain easily, to make my nitric go further many times I will dilute mine quite a bit more (to help keep gases in solution), this may take me a little longer to dissolve the silver, but time is cheaper than nitric for me, I will also add a little H2O2. and use heat after the initial reaction to dissolve the silver, with this process I can completely react all of the nitric acid as long as I have some silver left in the end, so many times I try to limit the amount of nitric I use compared to the amount of silver involved and add small portions of dilute nitric towards the end of the process, to put some more of that excess silver into solution. 

I do not know how well I explained this, but diluting your nitric and using heat at the end of the process to consume the nitric acid (leaving some silver at the end) will consume the nitric acid, when done right you can load the remaining water solution with quite a bit of dissolved silver nitrate salts.


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## butcher (Nov 10, 2013)

This time I also tried to remove oxide layer from grains, by first taking out undissolved grains washing them with water several time, drying them completely , then immersing them in HCl for 5 min, again water washing them and drying them completely. On putting them in old Nitrate solution, reaction starts vigorously and very soon they become passivated again.

I am not sure but by removing and drying you probably could oxidize the Pd oxide layer further (possibly from pdO to PdO2), I do not know.
HCl will dissolve the oxide, but once this oxide is dissolved HCl will not attack the remaining Pd metal worth a darn, and your introducing some chloride to your nitric when you put this back into you nitric solution (not too much of a problem here, but I see no reason to do this,I am thinking it could just complicate things further.

Maybe someone who has worked more with palladium will chime in here.


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## rcarbon (Nov 10, 2013)

Yes you are 100% correct in both of your replies. I am also thinking , exactly the same.

The only thing amazing me is that how come I managed to dissolve so much of Pd in just a small amount of Nitric.
And now on repeating of same, now I am not getting the same results, This make me belive that earlier MAYBE UV rays from strong sunlight helped.


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## butcher (Nov 10, 2013)

Yes it can reduce some of the nitric to NOx gas needed for the reaction.


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## niteliteone (Nov 10, 2013)

What is the temperature of the acid solution now compared to 4 months ago :?: 
Sun light does have UV rays that will decompose the nitric acid, but of more importance is that it will also "Heat" the acid solution. This heat will determine how fast the reaction will happen and also how much metal can be dissolved with that amount of acid.
Are you using cold acid with this experiment or are you heating it :?:


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## 9kuuby9 (Nov 11, 2013)

4metals said:


> 15% Kryolite
> 35% Borax (anhydrous)
> 25% sodium nitrate
> 12 1/2% soda ash
> 12 1/2% slaked lime



How many melts would a clay graphite crucible survive using this flux mixture? (approximate)


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## rcarbon (Nov 11, 2013)

niteliteone said:


> What is the temperature of the acid solution now compared to 4 months ago :?:
> Sun light does have UV rays that will decompose the nitric acid, but of more importance is that it will also "Heat" the acid solution. This heat will determine how fast the reaction will happen and also how much metal can be dissolved with that amount of acid.
> Are you using cold acid with this experiment or are you heating it :?:




4 months ago everything was carried out at room temp of about 28 - 32 C absolutely no external heating was involved.

now I have tried at room temp of 11 - 13 C, also used external heating till 85 C, but did not achieve results like previous one


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## butcher (Nov 11, 2013)

Chemical reactions can be exothermic or endothermic.

Exothermic reaction, evolution of heat. Example heat produced by the chemical reaction of nitric acid dissolving silver.
In exothermic chemical reactions chemical energy is usually converted to heat energy but can also form other kinds of energy changes, liberate light without heat, or electrical energy without light or heat.
http://en.wikipedia.org/wiki/Exothermic


Endothermic reaction absorption of heat. Example reaction of the cold pack where water and ammonium nitrate come into contact pulling heat from the surrounding area.
In endothermic reactions heat energy, light energy or electrical energy is converted into a chemical energy.
http://en.wikipedia.org/wiki/Endothermic

Dissolving a metal in nitric acid produces heat as energy by the chemical reaction.

Chemical changes do not always involve energy changes, and some energy transformations do not involve chemical changes. Example heat energy may be converted into electrical or mechanical energy without chemical changes.


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## niteliteone (Nov 11, 2013)

rcarbon said:


> niteliteone said:
> 
> 
> > What is the temperature of the acid solution now compared to 4 months ago :?:
> ...


Well it was worth a shot.
Where I live it is +/- 100*F through-out the summer and down in the 30's over the winters. This has a big effect on working with chemicals year round, when working with ambient temperature chemicals.
Over time I have learned to only work with heated solutions when dissolving metals, as it takes the guess work out of how things will react this time compared to the last.


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## freechemist (Nov 15, 2013)

Some of my practical lab-experiences dissolving palladium:

*1.) General:* Constant stirring is a must, also heating is often necessary.

*2.) Digestion in AR:* Palladium, to dissolve in AR is a dog, especially as Pd-black, also suspending Pd in HCl and adding HNO3 in small increments. Without heat not much happens. At 70-80oC digestion appears to run smoothly, but can, without any evident reason, come to a stillstand. Further heating and stirring, especially when adding a small portion of HNO3, often may lead to a sudden boil-over, mostly resulting in a big mess. Dissolution is always accompanied by escape of copious amounts of NOx.

*3.) Digestion in nitric acid:* Needs a lot excessive acid; at least about 2.15 ml 65%HNO3 are used to dissolve 1 g metallic Pd. Calculation based on the assumption, that 1 mole of HNO3 is used to oxidize 1 gram-atom Pd to Pd(II), and 2 moles HNO3 are needed, to hold it in solution as palladium nitrate, Pd(NO3)2. Heat helps to accelerate the reaction. While digesting Pd in HNO3 only small quantities of brown NOx escape, like *rcarbon*, apparently a very good observer, has observed it, too. If the digestion reaction does not start, addition of a few crystals of solid NaNO2 (sodium nitrite) is helpful, as well as adding about 1 ml of 1% KI-solution for each gram of Pd.

*4.) Digestion in sulfuric acid:* A lot of excessive 62% sulfuric acid (a mixture of equal volumes of 96% H2SO4 and water) is used as the "base-solvent", while oxidizing with about 1.1 moles of HNO3 (as 65% HNO3) per gram atom of Pd. The resulting solution has to be strongly acidic, and all Pd should be dissolved formally as palladium hydrogensulfate, Pd(HSO4)2. The digestion reaction delivers only small quantities of brown NOx, which cannot be driven out quantitatively, even by prolonged, strong heating. An intermittent passivation of metallic Pd has never been observed in this digestion reaction. Difficulties starting the reaction can be overcome, as in #3 above.


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## solar_plasma (Nov 15, 2013)

> addition of a few crystals of solid NaNO2 (sodium nitrite) is helpful, as well as adding about 1 ml of 1% KI-solution for each gram of Pd.



Just to get it right:
NaNO2 *or* KI...

or did you mean NaNO2 *and* KI?

..very valuable info, thanks!!


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## freechemist (Nov 15, 2013)

> *Solar_plasma wrote:*
> Just to get it right:
> NaNO2 or KI...


It's *"or"*. Both do their job to the operators satisfaction.


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## rcarbon (Oct 26, 2014)

whats the best method to make Palladium hydroxide from Palladium dissolved in AR,


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## Lou (Oct 26, 2014)

Add NaOH?


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## rcarbon (Oct 26, 2014)

I am trying to make pure Cl free Palladium nitrate. Some times palladium does not completely dissolves in Nitric Acid. If I dissolve it in AR then convert to Palladium Hydroxide, and then completely wash it, and then add little nitric acid,
will i be getting back, Cl free pure palladium nitrate ?

Please explain. Also please do let me know any other method to get rid of Cl.

Thanks


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## Geo (Oct 26, 2014)

You can drive off chlorine with heat. I may be mistaken but Paladium will dissolve in hot nitric acid.


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## rcarbon (Oct 26, 2014)

In past I have tried several times, but every time Pd supplied by various or same supplier behaves differently.

Some times it simply melts in hot Nitric acid like butter in just 2 hours and sometime it dissolves on 10 - 15 % in same amount of acid under same conditions , even in 48 hours


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## Smack (Oct 27, 2014)

It must have been alloyed then. Same material and conditions, same results, different material same conditions, different results.


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## Harold_V (Oct 27, 2014)

rcarbon said:


> Some times it simply melts in hot Nitric acid


I find it strange that you can heat nitric acid hot enough to **melt** palladium. 

Harold


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## rcarbon (Oct 27, 2014)

it doesn't has to be hot enough, I have experienced this at temp of of about 75 - 85 C


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## butcher (Oct 27, 2014)

rcarbon,

You can only melt palladium metal with very high heat, nitric acid would not survive that kind of heat.
You can dissolve palladium in nitric acid, but no matter how hot you get it, you will not melt palladium in nitric acid.


You are using the wrong words to describe what you mean to say, you cannot melt palladium in nitric acid.
This makes it hard for others to understand what your asking or talking about.

Using the correct terms or words will help others understand you better, and does not lead to as much confusion as to what is being discussed, when we use the correct terminology in our discussions, it makes what we say, easier for others to understand what we are saying, it can also help us get better answer to our questions, we all need to try and learn the correct terms to use in our discussions, not only for others but for ourselves.

Spend some time to find the correct word or term, this will help you, and us on the forum, to get a better understanding.


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## kurtak (Oct 27, 2014)

rcarbon said:


> it doesn't has to be hot enough, I have experienced this at temp of of about 75 - 85 C



I think you missed Harold's point completely - he finds it strange that you can heat nitric acid hot enough to "melt" palladium --- because metals are NOT "melted" in acid - they are "dissolved" in acid

The bigger point being made here - & a big part of the reason you are not getting a lot of help with what you are trying to do is that as a "new member" you have not yet taken the advise given to all new members which is to take the time to read Hokes book & read it until you understand it - then take more time to do research here on the forum & do so until you understand what is being done in the different processes --- we ask new members to do this so they can get at least a basic understanding about this & the reason for that is so that when you start asking questions you do it in away that is talking on the same page as the rest of us :!: 

Right now everything you are doing is WRONG --- the way you are processing your metal is wrong & the words you use to ask your questions are wrong --- & that's because you have not yet done your "home work" (research & study) --- we will not help you because we can not help you until you do your home work & get on the same page - its that simple

Here are two links you NEED to read - the first one drives home Harold's point - the second one will help you get headed in the right direction for doing your home work including providing a free down load of Hokes book

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=33&t=19074
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=33&t=21374

Kurt


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## rcarbon (Oct 27, 2014)

I do apologize for my wordings


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## 4metals (Oct 27, 2014)

> I find it strange that you can heat nitric acid hot enough to **melt** palladium.



Just a short refining story to show you what can happen by using the wrong term.

Back in the late '80's I owned a refinery and one of the services we provided was chemical stone removal. One day while I was out a client came in with over 200 ounces of gold jewelry scrap for chemical stone removal. If I was in the office that day it would not have been a problem because I was aware that people from India refer to digesting gold in acid as "melting". 

The secretary wrote up the receipt as a melt because that is what the customer said. He signed the receipt and left the job. 

The job was placed on the incoming melt shelves and one of the melt shop staff melted it, no biggie, it melted fine and made a nice bar. Well needless to say, the customer was not happy with the result. After his attempt to sue me for ruining a gadzillion dollars worth of diamonds I only escaped financial ruin because he signed the receipt and the receipt said melt.

He didn't mean melt, but it is quite possible that in India that is what it is commonly called. But he was doing business in the US, and business is conducted in English. (At least my business was conducted in English!) That was the way the judge put it.

Ironically we are all participating in a forum that is conducted in English, that is why we have to be careful to choose the right wording. 

Fortunately Mr Carbon's mistake will not cost him any values but I give this example to show why Harold will respond as he does. He is really trying to save our members from unnecessary problems.


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## Lou (Oct 27, 2014)

If you seek it to be chloride free, you can either titrate with AgNO3 and accept Pd losses on the AgCl; reflux the mixture with nitric acid to distill off Cl- as chlorine; not use chlorides in your process and buy Pd black that dissolves well in HNO3.


Alternatively, you can make the hydroxide and dialyze it in conductivity water to remove chlorides.

Lou


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