"Bromate Hydrolysis" Revisited

[Lou]

In order to get spot or better it has to meet the relevant ASTM specification for purity, in the case of a medical device company, 99.99%. Jewelers are often fine with 3N Pt so long as it is lead free and rolls.

While you can tell a lot by the color of the yellow salt (and what contaminates it), past 3N the subtle visual clues are harder to see. When very pure, the yellow ammonium hexachloroplatinate is fluffier and not nearly as dense. The same I suppose is true of other PGM salts.

 

[RaoOvious]

While you can tell a lot by the color of the yellow salt (and what contaminates it)

Compliment appreciated Lou 8).Obviously anything above 3N is harder to tell by mere color and is measured by %age impurities by MS.What was the assay after multiple hydrolysis on that crude?

Rao

 

[Lou]

After one hydrolysis and reduction, the purity is 99,99 by difference. Bear with me, I'll reorganize it to show the process.

 

[RaoOvious]

Sure..

 

[HAuCl4]

What's the shortest time for complete hydrolysis?. 15 minutes or more like 19 or 20 ?. :lol:

 

[Lou]

From negative pH to 0.5, rapid, 0.5-3.5 a half hour. From 3.5-8, 4-6 h depending on how the hydroxides flocculate. It's best to use a metering pump and a PLC to control it.

If the neutralization goes too fast (particularly for the other PGMs), they make precipitates which settle very slowly and do not rinse well. Bromate (or chlorine sparging), serves two functions--keep all base metals and platinum sister metals in the highest oxidation state where they are least soluble and not as inclined to colloidal suspensions, and also to slowly form by hydrolysis of their oxoanions the oxides. Slow formation allows for better ripening of the precipitate, improves purity and yield.

The boiling is done to ensure enough kinetic energy in the solution to allow for agglomeration, to expel elemental bromine and remove it from the equilibrium, and to maintain a close-to steady state concentration regime.

All of the boil off should be saved as trace values may report. The boil off can be acidified with HCl and used to treat the hydroxide cake for recovery of the other PGMs.

 

[HAuCl4]

Can it be said that if there is no Rh in solution, the hydrolysis can be done faster, and the precipitates separated easier?.

In my very limited experience, two sequential hydrolysis-filterings of less than 30' each produce finer Pt than a lengthy one of 3 hours. (Handling 1-2 oz amounts. Very lab scale. Inexperienced operator too. ).

 

[RaoOvious]

Depends upon PMG to BM ratio as well as Pt. to other PGM ratios and other factors already elucidated.

 

[HAuCl4]

Depends upon PMG to BM ratio as well as Pt. to other PGM ratios and other factors already elucidated.

I guess it also depends on the amount of sodium glutamate you add or if you don't use MSG. That's as useful in the real world as your reply. No offense, but it is what it is. :shock:

Just not to make this post a complete waste:

If you chlorinate your solution, and Sx it using TBP, Rh will stay in the aqueous phase, and then when you strip your TBP off, you'll have mostly Pt contaminated with Ir. This is MUCH MUCH MUCH easier and faster to clean by hydrolysis than a solution with Rh, Ir, Pt. 8)

 

[RaoOvious]

Depends upon PMG to BM ratio as well as Pt. to other PGM ratios and other factors already elucidated.

I guess it also depends on the amount of sodium glutamate you add or if you don't use MSG. That's as useful in the real world as your reply. No offense, but it is what it is. :shock:

Just not to make this post a complete waste:

You asked for the shortest time; "PGM to BM ratio and Pt. to other PGM ratio" was meant to explain;let me put easily so that you can correctly understand, that if their are other BM's then slow PH rise would give smooth separation and flocculation and thus would take more time not your "15 minutes or more like 19 or 20 ?. :lol:" and if your impurities are mainly other PGM's then you can devote your efforts from PH 4.5 to 8 and thus changing the time required to complete the separation efficiently.

And I was disappointed to see your technical and professional expertise suddenly reach at the highest levels of Sodium Glutamate.And finally this post wont be a waste unless some precious pearls like 'Glutamate' would be propagated.A wise man learns through signs not literature.Everything mentioned above is an honest representation.

 

[HAuCl4]

Thank you very much!. Everyone else here knows that my PGM chemistry understanding is completely incomplete. :lol:

 

[Lou]

So is mine. As the saying goes, just when you think you've seen it all...

Iridium is harder to remove than rhodium.

 

[RaoOvious]

Its a good motivation then,for all.........who r trying to zigzag in the course... :arrow:

 

[HAuCl4]

I just wanted to mention that this method evolved from an analysis method devised for samples without any base metals, silver or gold. There are probably several good reasons for that.

 

[RaoOvious]

Yes Gilchrist and Wichers's work involved solely six PGM's(Pt,Pd,Rh,Ir,Os,Ru) without any BM's,Gold and Silver but the very theme and chemistry of Hydrolysis can also very successfully encompass these too.

 

[RaoOvious]

Platinum Mother Liquor,after hydrolysis ready for bromine expulsion...

MS difference (impurities) is .0004.

I wish i could also upload the pics of settled hydroxides of Pd,Rh and Lead.

 

[Lou]

Looks very dilute; still needs filtered. It should be crystal clear orange after it is done.

 

[RaoOvious]

Bromine expulsion through HCl was still to be done on that piece,but after so doing it became as you pointed.I,ll post some more pics..

 

[Lou]

What elements did you subtract on the ICP-MS?

 

[lazersteve]

Here's what my platinum solutions look like before I precipitate:

The beaker is in a stainless bowl ready for the ice bath for precipitation.

and a more dilute one:

One from the top down into the beaker:

and of course the always delicious extra large Pt Banana Milkshake

Steve