Palladium in various states of process

I've threatened for some time to post a picture of samples of palladium that I kept from my refining years. Below, you will see five sample bottles, along with one of the new US $1 bronze coins.

The first specimen, left side, contains palladium that was precipitated with ammonium chloride and sodium chlorate. The salt was then dissolved in ammonium hydroxide and re-precipitated with HCL. The color changes from red to pale yellow, as you can see.

The second specimen is palladium precipitated with ammonium chloride and sodium chlorate.

The third specimen is palladium precipitated with dimethylglyoxime (DMG). Note the bright yellow color.

Fourth specimen is calcined palladium salt----in this case precipitated with ammonium chloride and sodium chlorate.

Fifth specimen is a small bead of palladium.

Harold

Great post Harold,

Now I have a good idea of what to look for when I precipitate my Palladium batch!

Steve

Is there difference's in the weight to volume ratio of the different precipitations?

If that is not quite clear what I am trying to ask is when the different methods are used, like the DMG, I believe you or someone posted elsewhere that it gives volumes of precipitation with minute amounts of Pd.....

In my reading, I see that there is always more than one way to skin a cat [or in this case precipitate Pd out of solution] I guess I want to know what is easiest, and then which would be the better to use when trying to bring it back to a button form [if you have a guess even] more than likely since I do not have an induction furnace access [though I have not checked up to the university of Idaho yet] I will more than likely use a torch to reduce the powders to metal form....

btw very nice and clear photo!

William

blueduck said:

Is there difference's in the weight to volume ratio of the different precipitations?

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I'm unable to answer that. I never bothered to make any determinations, for I never had to account for the platinum group so recovered. As a result, I wasn't concerned with ratios. The salt reduces considerably in volume when it is calcined, so it's quite light in weight as compared to the sponge.

If that is not quite clear what I am trying to ask is when the different methods are used, like the DMG, I believe you or someone posted elsewhere that it gives volumes of precipitation with minute amounts of Pd.....

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It's clear for me----and I'd comment that using DMG for precipitation isn't the smartest thing you can do. While it will precipitate the most dilute of solutions, the volume of precipitant is huge----and as I've mentioned, not easy to handle. When dry it tends to stick to everything it touches. The other methods yield tiny crystals that are more like sugar---so they handle quite well---but are water soluble, so they must be handled with dry utensils. Using a washing bottle, traces left behind in handling are easily washed away to the stock pot , where they are stored for future recovery.

If the concentration level isn't high enough to precipitate with ammonium chloride and sodium chlorate, I highly recommend it be either evaporated, or poured to the stock pot, where it can accumulate and increase the volume for future recovery en mass. The process of recovering palladium is slow and tedious---and not worth taking the time to recover in small volumes. You'll understand this better after having done it a few times.

In my reading, I see that there is always more than one way to skin a cat [or in this case precipitate Pd out of solution] I guess I want to know what is easiest, and then which would be the better to use when trying to bring it back to a button form [if you have a guess even] more than likely since I do not have an induction furnace access [though I have not checked up to the university of Idaho yet] I will more than likely use a torch to reduce the powders to metal form....

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Please read Hoke's book on reducing the salts. Doing it with a torch can be a mistake. It should be heated slowly, so as to not drive off values when calcining. Further, a direct flame would be inclined to blow some of the salt away. It's a slow process, one that would take too long to achieve with a hand held torch. I used a Fisher type burner, with a Vicor or quartz melting dish held in a ring. A batch might take as much as a half hour. The calcining operation is best accomplished in a hood. The smell leaves a great deal to be desired, and is likely not good to breath. I avoided doing so by doing the operation in the mouth of my hood.

An induction furnace is not necessary for melting palladium, and can even be avoided with platinum for small volumes. A large Hoke torch, or even an oxy/acet torch with a rosebud can be used with success. The tip should be well cleaned before application, to avoid contamination from scale.

If you're not familiar with induction furnaces, I'd encourage you to do some research. Just having one may not be the solution. As volume increases, frequency of the induction furnace can be reduced. Large induction furnaces (capable of melting many tons of metal) can run line frequency, but as volumes are reduced, the required frequency to melt must increase. To give you an idea, I own a 50kw Ajax Magnethermic power supply--which is capable of melting up to 200 pounds of metal, assuming you have the proper furnace. It runs @ 3,000 Hz, but they also made one of the same capacity that operated @ 10,000 Hz. As the frequency increases, they are capable of starting with smaller feed material. You might not be successful achieving a molten mass starting with fine particles at 3,000 Hz, where with a 10,000 Hz machine you could, as an example.

There is a published chart that shows optimum frequency for given loads, which would be a good reference for those that might be interested in exploring induction furnaces.

A microwave oven is nothing more than a high frequency induction furnace. Anything can be heated by induction if the frequency is high enough.

btw very nice and clear photo!

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Thanks. I use a Sony FD-97 that's about 5 years old now. It's proven to be a good camera---although somewhat large in size. It records to a floppy disc, or a memory stick, which I do not have. Very easy to take pics, then remove the disk and insert it in the floppy drive of the computer. No cables required.

Harold

http://webpages.charter.net/dawill/tmoranwms/Electronics.html

Sorry to resurrect and old thread, but this fellow has done a lot of work on the small scale (<10 kW) with inductions furnaces. As Harold's already mentioned, they're not required, but they are very nice to have as they melt quickly, cleanly, and efficiently. You can also melt your metals in a vacuum.




Also, I wouldn't use DMG as it will also drop out any nickel in there as well. Dimethylglyoxime is also pretty expensive, and fairly toxic as well.
Ammonium chloride + sodium chlorate works very well. If you don't have chlorate and don't want to make it from salt (easy to do), you can make chlorine gas with manganese dioxide and HCl and bubble that through a warm solution. Then chill it all and most of your precipitate crashes out as a nice brick red slimy precipitate.

For any of you that care to make your own chlorate for a buck a pound...
http://webpages.charter.net/dawill/tmoranwms/Chem_Chlorate.html



Lou

This was presented in earlier threads to dissolve Gold by generating Chlorine gas in situ. It might also make a good Chlorine gas generator for the Precipitation of Palladium complex.

Dear Harold,
Is it possible that the subject material
is Palladousammine dichloride? the
color about fits.
Lino1406

Lino1406 said:

Dear Harold,
Is it possible that the subject material
is Palladousammine dichloride? the
color about fits.
Lino1406

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Chuckle!

You're asking a guy that struggled to graduate from high school, having taken no chemistry classes, a question like that?

Certainly could be------but I'd have no way of knowing. I welcome your input.

Harold

The brick red is your (NH4)2PdCl6, ammonium hexachloropalladate in its +4 oxidation state and that is the start of your pyrolysis pathway for palladium. At about 350C it goes to palladite, the +2 oxidation state.


The way you're naming sounds like it’s complexed with NH3. Nope, it's actually an ammonia salt. Don’t even get me started with why it’s a salt not a complex and not vice versa…

I’ve been meaning to post this up for a while. I won’t mention Ru, Os, Ir, and Re unless y’all ask me to, since not many people deal with it. Same with some of the other weird compounds that you rarely ever see, like platinum oxide (sounds like an oxymoron doesn’t it )To the CRC (my Hoke ):
The properties of Palladium, platinum, rhodium and their common salts:

Palladium
Pd-palladium, 106.42 g/mol, melts at 1554.9oC. Soluble in aqua regia, nitric acid, conc. sulfuric, and Cl2+ HCl to give a deeply yellow solution that appears brown.

(NH4)2PdCl6—ammonium hexachloropalladate (IV)—355.21 g/mol. Brick red hygroscopic crystals. Soluble in hot water, concentrated ammonia. Reduce to sponge with heat or hydrazine, Pd black with formic acid or borohydride.

PdCl2—palladium (II) chloride—177.33 g/mol. Ruby red hygroscopic crystals. Soluble in acetone, (m)ethanol, and water. Reduce with hydrogen, 500oC.

PdO—palladium (II) oxide -- 122.42 g/mol. Greenish black crystals. Insoluble in water, readily soluble in aqua regia. Palladium hydroxide is a hydrated form of this compound. Reduce with ammonium formate or heat til dissociation of the elements at 750oC.

Pd(NO3)2—palladium (II) nitrate—230.43 g/mol. Brown hygroscopic crystals. Slightly soluble in water, very soluble in dilute nitric acid. Reduce with pyrolysis.

Platinum
Pt—platinum, 195.08g/mol. Melts at 1768.4 oC. Soluble in hot aqua regia, practically nothing else. Gives a red orange solution.

(NH4)2PtCl6 – ammonium hexachloroplatinate (IV) – 443.87 g/mol. Orange-red cubic crystals. Slightly soluble in hot water, conc. ammonia, insoluble in ethanol. Reduce to sponge with heat or hydrazine, Pt black with formic acid or borohydride. Alkali metal analogues.

(NH4)2PtCl4—ammonium tetrachloroplatinate (II)—372.97 g/mol. Dark red crystals. Soluble in water. Reduce to sponge with heat.

H2PtCl6*6H2O—hexachloroplatinic acid hexahydrate—517.9g/mol. Brown-yellow hygroscopic crystals. Soluble in HCl, very much so in water and (m)ethanol.

Rhodium
Rh, rhodium 102.91 g/mol, melts at 1964 oC, really damn hot. Slightly soluble in aqua regia and fuming sulfuric acid. Best dissolved by fusion.

RhCl3—rhodium (III) chloride—209.264 g/mol. Red to chocolate brown crystals. Soluble in alkalis, strong acids; insoluble in water. Reduction with hydrogen at 500 oC gives clean Rh sponge.

Rh2(SO4)3—rhodium (III) sulfate—494.002 g/mol. Red-yellow solid, brown solution. Slightly soluble in water, more so with sulfuric acid. Decomposes to the oxide at 500 oC. Cement with merrilite zinc or magnesium turnings. Or plate, or reduce the oxide with hydrogen.

Rh4(CO)12--Rhodium [dodeca]carbonyl—747.747g/mol. Red crystals. Decomposes with water or heat to yield rhodium metal.

Thanks Lou and Harold
You gave me the answer, since:
The subject material, Pd(NH3)2Cl2
is received from PdCl2 by the method
Harold mentionned, that is NH3, followed
by HCl - no need for chlorate in between
and the Pd there is +2. Now, if Pd+4 gives
the same color to Pd+2 (which personally
I doubt), that could be interesting, or - some
traces of Pd+2 have been also present there
despite the oxidation by chlorate...
(words words words but how interesting)
Lino1406

ok Pd(NH3)2Cl2, diamminopalladous chloride is a complex salt. Acidification with peroxide will probably make (NH4)2PdCl6, or skip the peroxide--the hydronium from the HCl will break the complex and make the ammonia salt.

Most complexes are really soluble, did you crystallize it out, or did it precipitate? If so, from what temperature solution?

Hello Lou,
This is very resistant precipitate
at room temperature. The exact
procedure: 1)Dissolve PdCl2 in
HCl, or take ready Pd solution
2) Add conc. NH4OH (or NH3)
to get some scattered yellow
red brownish particles.
3)Add fluently NH4OH, this should
dissolve most of the particles
4)This part is a bit nasty, add
HCl carefully (much boiling and
smoking), and you get it at once.
You may want to wash it with alcohol.
Lino1406

Lino,

That is the exact same procedure I use to redissolve and purify my red Pd salts and complexes from ammonium chloride + sodium chlorate precipitations.

Hoke outlines it in her book.

By the way Lou,

I tried Irons idea to simply add sodium hypochlorite 5% (bleach) to the ammonium chloride, HCl, and palladium solution. It worked like a charm. Looks promising for eliminating the the sodium chlorate as a precipitation reagent with Pd salts and complexes. There is still a very fine balance of ammoinum chloride and chlorine required.

Steve

Interesting. I had envisioned using the Hypochlorite/HCl as a separate Chlorine generator to minimize the addition of more water but adding it directly scavenges excess HCL. I'm a little leery about adding any more spectaror ions that would increase contaminants.

In an earlier thread, I had proposed to bubble Ammonia gas directly to scavenge the excess HCL and convert it to Ammonium Chloride in situ. This would reduce the water even more. The Ammonia comes from the Nitric acid production from Ammonium Nitrate and Calcium Hydroxide to produce Calcium Nitrate which is reacted with Sulfuric Acid togive HN03 and Calcium Sulfate as a precipitant.

Ammonia is also good for converting any excess Nitric Acid to Ammonium Nitrate which could be recycled back. This might be useful where Palladium is digested in Nitric alone.

Irons,

I agree with you about adding too many ions to the solution. I was just doing a quick small scale test of the idea and it seemed to work. A separate generator setup would be much cleaner, but would involve more labware.

Since the resultant Pd complex is only slightly soluble in dilute (15% >)ammonum chloride solution the extra water doesn't seem to be a factor. The key is to produce ammonium chloride (NH4OH + HCl ) in situ or add in enough solid NH4Cl to prevent the resulant complex from redissolving when the Cl2 is added.

Steve

Having a Chlorine generator is handy when working With PMs. HCl+Cl makes for a clean dissolution. I's like the analog to using SO2 to precipitate Gold rather than SMB. They both work but the gas gives a cleaner product.

Calcium Hypochlorite is available cheaply at pool chemical suppliers and all you need is a HCl drip to generaate the gas. It's also available in cylinders, as is anhydrous Ammonia.

I wasn't trying to be critical, just a nitpicker. :

BTW, Anhydrous Ammonia is also great for getting rid of Gophers. Stick the hose down the hole and pack dirt around it to keep it from blowing out. Trust me, a face full of anhydrous Ammonia is something you won't forget.

I'm with you Irons, the less spectator ions in solution, the better! I usually use SO2 for my first Au precip, then oxalic acid the second time round. The sulfur dioxide is in a lecture bottle, and so is my chlorine. It's kind of hard/expensive to get chlorine and sulfur dioxide cylinders nowadays.



Hypochlorite will work instead of chlorate, and so will hydrogen peroxide and HCl (forms your chlorine in situ thru hypochlorite). You need an oxidant to get free chlorine and your solution must be strongly acidic. Irons, it will scavenge only so much HCl in dilute solution because there's an equilibrium between the chlorine formed from OCl- and OCl- formed from the chlorine! That is how I make strong 12% bleach, using chlorine gas and cold sodium hydroxide solution.

Awhile back I did a good sized precipitation of the ammonium hexachloropalladate salt in a 4L beaker. Probably 500g worth. I did the precipitation with excess HCl and a little bit of sodium chlorate to make free chlorine (that's owing to the fact that I couldn't get the damn chlorine cylinder open, it's really corroded). I also added about 130% of theoretical amount of ammonium chloride in several portions with magnetic stirring.

The precipitation was done hot, then the whole lot of it was chilled in an ice bath, volume decanted, and then vacuum filtered. I held back some of my ammonium chloride solution and acidified it slightly, chilled it, and used that for rinsing my precipitate in the buchner. Extra ammonium chloride has no effect on the reduction of your palladate salt.

I'd use bleach, but it's a real pain to make it up (I don't use store bleach) and I've got plenty of chlorate laying around.

It's good to have different options to do the same process depending on what you have available or is easy and inexpensive to get. Many of us live in the boonies where chemical supply houses are few and far between and shipping and HAZMAT charges can really cut into profit.

I'm sure we've confused a lot of people with all of the different variations and the techniques to adapt chemicals becomes more of an art form than cookbook chemistry.

The best thing for newbies is to stick with the tried and true procedures and leave the experimentation to those with those who understand the pitfalls.

Buy the Hoke book if you're not sure what to do. Mistakes in processing can be very expensive and sometimes hazardous.

I learn something new every day, especially since joining here.

I seem to hear a lot of good about this Hoke book. I think I'm going to have to look around for it. Is it more on the practical/cookbook side than it is on chemistry?

Written in 1940 by a lady no less. The tried and true methods of every want to be refiner for over 67 years. The one the only C.M. Hoke :arrow:
http://www.lmine.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=17205&Category_Code=assaying&Product_Count=3