# "Bromate Hydrolysis" Revisited



## RaoOvious

Does any one know exactly what was the total and individual weight of all six pgm's in the experiments conducted by Gilchrist & Wichers in the known article *"A Procedure for the Separation of the Six Platinum Metals from One Another and for
their Gravimetric Determination"*


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## Lino1406

Bromate is an oxidizer not hydrolizer


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## RaoOvious

sure bromate is an oxidizer but I m referring to Sodium bromate here, used in specific hydrolysis of Pd,Rd & Ir thus leaving behind highly pure Pt sol.,those who deal in this know this.


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## Lou

How much they started with for all the experiments is listed somewhere.


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## RaoOvious

That was the intention precisely, where?


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## kadriver

I stumbled on the document you are refering to (I think jimdoc posted it in the books forum) and was amazed at the apparent simplicity of the process.

I was wondering if the Pd should be removed first with nitric before starting the hydrolysis, or is it easier to get the Pd out after getting the Pt.

It looks like something ka could do!


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## RaoOvious

Hey kad,

The best would be to do it on impure platinum sponge (after precipitating Pt with NH4Cl and reducing it to sponge),although it can also be performed on whole pgm blacks but that would be inefficient.Regarding the weight of individual metals in the specimen,its not mentioned in the published article of Gilchrist and Wichers.

And removing Pd from mixed bag through Nitric is also severely inefficient,there are ample other options to do the task with minimal hassle.

Hintrop Pt and Pd through orthodox methods and then go after specialized tools to get high purity.

By the way nice to hear from u after so long,whats going on lately?


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## freechemist

Hi RaoOVius,

About the subject of hydrolytic reactions in analytical separations of different PGM's from platinum in solution there exist several publications (Gilchrist, Wichers, and others), but the one you mention contains no details about preparation and quantities of individual PGM's dissolved, Pt included, of the solutions to be examined. There are however two important citations of work, done by german or austrian researchers on the subject of combined bromide/bromate-hydrolysis:


> _Quite recently, Moser and Hackhofer have reported on the separation of iridium from platinum, and Moser and Graber on the separation of rhodium from platinum, by a hydrolytic procedure in which the alkalinity is fixed by the reaction between bromate and bromide ions. This reaction, however, appears to come to equilibrium so slowly that prolonged boiling and digestion is required to complete the precipitation._
> 
> L. Moser and H. Hackhofer, Monatsh., vol. 59, p. 44, 1932.
> L. Moser and H. Graber, Monatsh., vol. 59, p. 61, 1932.



In my practice this bromide/bromate-hydrolysis became a valuable tool, especially working up Pt/Rh and/or Pt/Ir-scrap of relatively low Rh-, Ir-percentage respectively, aiming for pure platinum. The chemical reactions, formulated for Iridium, are the following:

Hydrolysis: IrCl4 + 4 H2O ==> Ir(OH)4 + 4 HCl. For completion the generated acid has to be neutralized.

Reaction of sodium bromide (NaBr) with sodium bromate and acid forms elemental bromine (Br2).
5 NaBr + NaBrO3 + 6 HCl ==> 3 Br2 + 6 NaCl + 3 H2O. This reaction uses up slowly the acid formed in the hydrolysis-reaction above, while prolonged boiling leads to volatilization of elemental bromine formed, thus driving the combined reactions to completion. Even a great excess of added stoichiometric NaBr/NaBrO3- mixture doesn't matter. If once iridium is precipitated completely, no additional acid is formed, and evolution of elemental bromine stops.

Regards, freechemist


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## lazersteve

Thank you freechemist!

Very informative as usual.

Steve


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## Lou

The most important aspects of bromate hydrolysis are:

1) slow pH rise. Most of the base metals are out before the Ir and Pd start to precipitate. Go too fast and they will not settle well and will retain more of the Pt mother liquor.
2.) constant presence of oxidizer to insure all PGMs in highest ox state.
3.) solution is free of (NO2)2PtCl6 by boil down. If it isn't, you won't effect as clean a separation of the PGMs.
4.) Rinse hydroxide cake with pH 7.5 or higher bicarbonate buffered water. 

If the material is over 99% Pt at start, it's possible to just add caustic to the purified solution and then reduce with hydrazine and calcine. Iridium often needs several separations. 

For high grade powders (ie 999%+ platinum such as Steve produces, though his is better in some instances), 8M HCl and chlorine sparging are pre-eminent. At 70 C, the powder will dissolve within 6-8 h. I prefer this over AR because the nitroysl complexes aren't there.


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## lazersteve

Lou,

You are a man after my own heart when it comes to Platinum refining (and purity)  .

I still want to set up a bromine rig one day and give it a go, just to say I did. My biggest problem is too much work and no free time to explorer new possibilities.

Steve


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## samuel-a

lazersteve said:


> I still want to set up a bromine rig one day and give it a go, just to say I did. My biggest problem is too much work and no free time to explorer new possibilities.



Same here... i wish we had just few more hours in a day....

Thank you guys for the interesting posts.


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## Lou

If I could just log on the dang forum with my computer I would post up a video or pictures of the process!!!!!!


Very frustrated.

Edit language :twisted:


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## RaoOvious

Appreciated Freechemist.

The beauty of the work of Gilchrist and Wichers is that inpite of being open ended in tools used(if you look minutely),the core of the subject is accomplished.With slight acute modifications the task can be done even more satisfactorily.

Nice modifications Lou.


Rao


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## RaoOvious

An acute observation for efficient hydrolysis is the crucial Ph control which is undoubtedly the most critical aspect.For this minimize the presence of HCL after complete elimination of NOx otherwise much Bicarb would be needed to attain the required PH's,which ultimately would increase the volume of Pt mother liquor,a highly inefficient scenario.

Moist dry the original solution,acidify with minimal Hcl,hydrate and then start hydrolysis. 

Rao


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## Lou

That's what we do, make a slush of it, add maybe 3 cc conc HCl for every t oz and then 0.6 L boiling distilled water. The bromate is added in three portions. If the bulk of the impurity is other PGM, it is best to add the major portion from 4.5-6. 

Done correctly, no flocculant is needed.


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## RaoOvious

There is another crucial aspect,always do hydrolysis in two patches,one at PH 6 or around and another at PH almost 8(Because some try to maintain 6 or 7.5 solely,another inefficiency) to get total segregation.Yes if done correctly no need for any flocculant.

There is a post by another member where main deficiency is the magnitude of mother liquor which is highly crude even if one uses a bit high intensity neutralizer such as carbonate.So the thing boils down to the volume of the main liquor and its manageability with ease.

Rao


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## HAuCl4

Lou said:


> 1) slow pH rise. Most of the base metals are out before the Ir and Pd start to precipitate. Go too fast and they will not settle well and will retain more of the Pt mother liquor.


Silver seems to also come out completely before pH 7, which makes this process also useful to super clean gold solutions, before precipitation.
Thanks to all, for all the nice tips.


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## Lou

This is OT but can you go into your hydrolytic gold method, HAuCl4. 

What base are you using?

I just want to state that no one here should ever add ammonia past pH to gold solutions--a yellow to yellow brown unstable precipitate is formed. Dry, it is very friction sensitive and will deflagrate with great violence and purple smoke. It is NOT a novelty item!


I would imagine KOH doesn't make it, missing the N atom.


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## HAuCl4

NaOH
http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=61&t=14808&p=151128#p151128
This does not attempt to separate PGMs with this "gold hydrolysis", because Pt will stay in solution no matter what. This cleans the solution from base metals and silver (main contaminant usually).


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## HAuCl4

Lou said:


> If I could just log on the dang forum with my computer I would post up a video or pictures of the process!!!!!!
> 
> 
> Very frustrated.


Copy pics/videos to data chip / phone / ipad and post from there or email to a trusted forum member. I'm sure Lazersteve or kadriver would not mind posting them for you.


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## kadriver

RaoOvious said:


> Hey kad,
> 
> The best would be to do it on impure platinum sponge (after precipitating Pt with NH4Cl and reducing it to sponge),although it can also be performed on whole pgm blacks but that would be inefficient.Regarding the weight of individual metals in the specimen,its not mentioned in the published article of Gilchrist and Wichers.
> 
> And removing Pd from mixed bag through Nitric is also severely inefficient,there are ample other options to do the task with minimal hassle.
> 
> Hintrop Pt and Pd through orthodox methods and then go after specialized tools to get high purity.
> 
> By the way nice to hear from u after so long,whats going on lately?



Hello:

I got a bad case of that nasty flu back in december - put me in bed for a week, and then two more weeks of not wanting to do anything except lay around.

Believe it or not, I still have the concentrated Pd solution that we were working on back in November.

It is just sitting there in a covered beaker. I need to get it going and convert it to sponge so I can get it sold.

I did make a nice chlorine generator using trichloroisocyanuric acid (pool chlorine tablets from Lowes hardware) and hydrichloric acid drip in my fume hood.

I know what to do, just been busy with other stuff.

I'll review the info you sent me and get this Pd going - maybe post some pictures of it.

Thank for your help.

kadriver


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## kadriver

So, after dissolving in AR (or HCL/Cl gas to avoid nitrosol compounds), drop Pt and Pd via ammonium chloride, sodium chlorate, then incinerate (calcine) to obtain impure sponge, then do hydrolysis on the impure sponge.

I've got a nice Cl2 gas generator, I am thinking of doing an experiment to dissolve mixed PGM blacks (or the impure Pt sponge) in room temp HCl, then bubble Cl2 gas through the mixture to dissolve.

*Has anyone ever tried this experiment?* 

I know HCl/H2O2 and HCl/sodium hypochlorite (bleach) methods. But I have never tried bubbling Cl2 gas.

Since it is new to me, I think setting up the gas generator and making the gas in my fume hood is much fun - for now.

Thanks

kadriver

Edit once to correct chemical name


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## Lou

Chlorine-HCl is my favorite method to dissolve sponge because it is clean and fast. I use AR only for bulk materials (clips, springs, wire, sheet).

You want to boil it after all the residue is dissolved, filtering if any insolubles like AgCl or silica are present. At this point, a drop or two of sulfuric is helpful to remove lead. Hopefully it is gold-free as it is much easier a process with more immediate return. If it is not, hydroquinone is indicated.

After you boil, all the Pd(IV) present is converted to Pd(II) while the Pt remains in its highest oxidation state with the Ir. At this point, precipitate the platinum with ammonium chloride. It will be contaminated with Pd, Rh and Ir. The Pd, Rh, Ir containing supernate (largely Pt-free) can then be precipitated as potassium hexachloropalladate with KCl and chlorine gas; the supernatant from that filtration can be treated with dimethylglyoxime and the recovered Pd(DMG)2 complex digested with AR and quickly boiled. I do not advocate for using KCl for platinum at this point, as it is difficult to wash K+ away whereas any residual ammonium chloride from the reduced ammonium hexachloroplatinate is oxidized when the sponge is re dissolved. I do suggest KCl for the Pd salt as this avoids the NCl3 issue in tepid solutions. 

The (NH4)2PdCl6 is dissolved in excess conc. ammonia (as is the DMG digest). It will be strongly basic (only way to dissolve pink Vauquelin's salt rapidly) and most impurities will be complexed as ammines. Let this solution stand overnight or simmer it to drive out dissolved excess ammonia. You may see a precipitate form in the near-neutral solution (hydroxides or AgCl). Filter this solution, rinsing with pH8 bicarbonate buffered water. This filtrate is acidified with conc HCl to pH 2-2.5 and the yellow Pd salt is filtered off, rinsed with ice cold 0.05 N HCl/NH4Cl solution until the filtrate runs completely clear. The Pd diammine chloride is treated with cold, concentrated ammonia and the (hopefully clear) solution is filtered (this removes any rhodium and Pt traces). This Pd is precipitated again as above, filtered/washed and the salt is treated with sodium formate at pH 3.5-5 in DI water at 65 C, and will quickly and quantitatively reduce. It should now be 99,9+ pure. All filtrates should go in for cementation (or IX if you have it) and be reprocessed with the next lot, after a good incineration and water leach to remove ammonium/potassium cations.

Return now to the ammonium hexachloroplatinate. Reduce it thermally or with zinc, giving it a quick rinse and being sure the acidic filtrate is colorless. Redissolve this platinum (syrupizing if using AR or the Rh may cause problems) and prepare for the hydrolysis. We will talk about that over the phone.

Hope this helps!


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## RaoOvious

Kad,

I hope you would further enjoy in your new endeavors. Yup you can dissolve Pd,Pt nd minutely Rd through your chlorine bubbling apparatus. I would suggest if you have a mix bag of PGM's(largely Pt,Pd,Rd,Ir) then dissolve them as per your favorite methods except its favorable to avoid any salt formation(as with hypochlorite),denoxx or dechlorinize, concentrate your pregnant solution to 1gm per 5ml, then precipitate using NH4Cl for Pt(along with Pd,Rh,Ir impurities), filter efficiently so that no supernatant solution remaining in your filtrate, reduce with dilute Hcl/Zinc nd convert to impure sponge "Feedstock for Hydrolysis".

As with filtered solution bubble chlorine or chlorate or chlorite, filter until precipitate is clear from supernatant remaining solution (scavenge this with zinc to add to the impure Pt sponge for Hydrolysis).

Remaining can be found regarding Pd in already discussed material.

Good luck and have fun.

(edited out text lingo Butcher)


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## HAuCl4

Is there a problem with using the TCCA directly in the metal reactor to avoid the chlorine gas rig?.


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## Lou

Yes there is a problem, cyanuric acid is produced as a byproduct. The less to filter the less you worry about entrapping values by entrainment. TCCA is the best way to make Cl2 safely (way better than other methods) and is easily controlled.


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## kadriver

The gas rig I have was relatively inexpensive and easy to set up. Plus its fun because its new to me.

I will get some photos and post them here when I chlorinate some palladium solution to make ammonia soluble (NH4)2PdCl6.

The most expensive piece was the equalizing funnel at $53 with free shipping.

Here is a picture of it (24/40 ground glass connections). Bought it on Ebay

http://www.ebay.com/itm/221173823773?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

kadriver


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## butcher

Nice tool, 
I appreciate you posting that, if I understand how it looks like it would work, you could have an acid in the chamber open the valve to drip acid into the vessel below, the small gas tube on the side would allow gases from the reaction to pressurize the space above the acid chamber, to assist in pushing the acid out through the valve, even into a pressurized vessel below the valve.


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## kadriver

Thats exactly how it works. The other funnel i was using would drip the acid in an irregular fashion.

The equalizing funnel completely eliminates the irregular flow and makes controlling the amount of gas produced a snap!

kadriver


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## butcher

I just had to get one, its too cool for gas generation.


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## HAuCl4

Lou said:


> Yes there is a problem, cyanuric acid is produced as a byproduct. The less to filter the less you worry about entrapping values by entrainment. TCCA is the best way to make Cl2 safely (way better than other methods) and is easily controlled.


Thanks Lou. What is 'entrainment' exactly.

I guess it depends on the feed that one is processing.

For gold dust, sponge after inquartation, or atomized karat scrap, mixing the TCCA with the metal, and dripping the HCl works extremely fast and clean. Since one has to filter and wash the AgCl cake anyway, it makes sense.


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## lazersteve

I prefer to use a separatory/addition funnel with a Telfon valve in the place of the glass valve. Teflon is less likely to stick and way less likely to break.

Steve


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## kadriver

I have never used a funnel with a teflon valve.

When I first started using the sep funnel with the glass stop it would stick something terrible and cause problems with getting it shut off quickly.

Then I bought some dow high vac grease and lightly applied to to either end (being careful not to get the grease near the hole in glass stop valve).

Now it operates nice and smooth.

I have not broken one of the glass ones - yet.

Do the teflon stops need grease like the glass ones do?

kadriver


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## lazersteve

Teflon is naturally slick due to it's low coefficient of friction. The Teflon valves have a couple rubber (?) o-rings that require a slight lube to keep them from drying out from chemical exposure, but for the most part, no lube of the valve.

Steve


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## Lou

Please be careful using PTFE (teflon) as a stopcock material! On hot solutions, especially with separatory funnels, the PTFE will expand and cause the joint to leak. The o-rings are usually Viton, which is generally pretty chemical resistant, but they are not made for aqua regia.

The only thermoplastics suitable for long term hot aqua regia exposure are PVDF, PTFE, FEP, PFA. Polypropylene and even CPVC will fail. Polyesters/amides and other condensation polymers are wholly unsuitable for strong acid or base. This is the grease we use for joints/o-rings, or anything getting really hot. I use it on my firearms too. http://www.vacuumoil.com/krytoxgrease.htm


Entrainment occurs when values get stuck in hydroxide cakes by adsorption and are not expeditiously or easily removed without compromising the purity of the solution. To me, it means the gradual collection of values in waste streams by attrition.

I'll post some examples of a pilot bromate hydrolysis. Here is preparing the feed...
when I'm back off my other computer I'll post the re-dissolve and some hydrolysis pictures.


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## RaoOvious

Lou;is the crude weight 118.97,1189.7 or 11897 gms?


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## necromancer

Lou said:


> If I could just log on the dang forum with my computer I would post up a video or pictures of the process!!!!!!
> 
> 
> Very frustrated.
> 
> Edit language :twisted:




how is it you log on to the forum ?


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## Lou

I can get on via proxy but can't post attachments. I was at my hotel to post last time.

Rao, that scale weighs in troy ounces, so it is closer to 3700 grams. That yellow powder is calcined at 850 C, then the chunks are ground up and redissolved, and then diluted to ~55 g/L and pH brought up to 0.5.

It's possible to just do the hydrolysis several times to rid of other transition metals, but that is more time intensive.


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## RaoOvious

IC, nice color though.R u going after 4N MB there because that salt looks fine to be having officially termed 3N MB Plat..And does this feed belongs to clientage?

Yes multiple Hydrolysis really demands time and close forbearance.

Rao


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## 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.


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## RaoOvious

Lou said:


> 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


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## Lou

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


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## RaoOvious

Sure..


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## HAuCl4

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


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## 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.


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## 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.  ).


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## RaoOvious

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


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## HAuCl4

RaoOvious said:


> 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)


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## RaoOvious

HAuCl4 said:


> RaoOvious said:
> 
> 
> 
> 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:
Click to expand...


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.


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## HAuCl4

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


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## Lou

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

Iridium is harder to remove than rhodium.


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## RaoOvious

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


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## 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.


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## 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.


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## 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.


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## Lou

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


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## 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..


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## Lou

What elements did you subtract on the ICP-MS?


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## 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


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## RaoOvious

.0002 Pb,.0001 Cr,.0001 Pd


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## RaoOvious

Further Sequel....


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## Lou

Nice pictures guys.

Steve,

Heartily advise the use of plastic containers 

Rao,

Why only those elements?


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## RaoOvious

Lou, would have to ask from MS Machine :| .Anyways 400 million nano grams per tr. is a bit ok.

Appreciated.


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## RaoOvious

Sequel.... 

Different angles of Purified Platinum Mother Liquor just before separation and then Reduction.....


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## RaoOvious

Another episode of Hydrolyses....Purified Platinum Mother Liquor of commercial purity before reduction....................And Inspite of the apparent simplicity of Hydrolysis process,there are procedures which are subjective.

Rao


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## Lou

Should mention that you should concentrate (at least reduce the volume by 1/2, if not 1/3 or more) then precipitate with ammonium chloride. 

Only in very few instances is it possible to merely reduce the solution as is--especially if the material is high in refractory metals.



Forgot to answer your question that prompted this nice thread...


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## RaoOvious

Lou, I got informed about the weights earlier,but in fact the weight-ages given(as per Gil.& WICH.) are in no way reflective of the amounts of reagents used in handling the different scenarios encountered(I am sure you would be aware of this).

And the purity of Platinum feeds was 999 in this episode so direct reduction will not affect CP, infact these liquors were hydrochlorized to get rid of remaining bromate and then were reduced.The recipient got more than CP(commercial purity).

Rao


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## HAuCl4

That MS machine is broken. hehe. :lol:


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## HAuCl4

Do they do the hydrolysis pre or post TBP at INCO-Matthey?. Or both?. :?: :idea: :lol:


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## RaoOvious

They dont LLX is smarter than old hydrolysis 8)


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## RaoOvious

* Platina's*

Small one(3.8 gm) was segregated by organo-metalic separation of other associated pgm element,big one(12 gm) has undergone bromate hydrolysis.Trade Recipient of those had a terrible cell phone camera and artistic taste to arrest those buttons(Which to even naked eyes were shining like Platina does :lol: )


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## DNIndustry

I know I shouldn't solicit on thread but I will just to offer the opportunity to try this.
If any one is interested I have all combinations of bromide/bromate salts and HBr etc. In bulk and small quantity.
PM me


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## Research135

RaoOvious said:


> They dont LLX is smarter than old hydrolysis 8)


Lou is doing hydrolysis by his own admission. The reason is likely purity, and / or speed over that obtained with solvent extraction. 
What a wonderful thread.


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## Lou

It's a tool, not a guaranteed way to hit ASTM specifications on platinum.


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## zachy

Hello boys

That other products can be used, to replace the sodium bromate to make the hydrolysis of the solution, sodium bromate is not obtained in my country, and I do not know with which hydrolysis can be done. please help


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## kadriver

I'm planning a new video on this subject. Ive got the Sodium Bromate to do the experiment. I'm going to follow the procedure given by one of the experienced members in one of these posts.

I'll make a detailed video of the entire process, if I can pull it off.

This will be another practice run in preparation for processing my stock pot.

Just wanted to pull the thread back up on top of the heap so I dont have to dig to find it.

kadriver


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## anachronism

kadriver said:


> I'm planning a new video on this subject. Ive got the Sodium Bromate to do the experiment. I'm going to follow the procedure given by one of the experienced members in one of these posts.
> 
> I'll make a detailed video of the entire process, if I can pull it off.
> 
> This will be another practice run in preparation for processing my stock pot.
> 
> Just wanted to pull the thread back up on top of the heap so I dont have to dig to find it.
> 
> kadriver



In that case all you need to do is subscribe to the topic. It's at the top of the page in the toolbar.


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## kadriver

anachronism said:


> kadriver said:
> 
> 
> 
> I'm planning a new video on this subject. Ive got the Sodium Bromate to do the experiment. I'm going to follow the procedure given by one of the experienced members in one of these posts.
> 
> I'll make a detailed video of the entire process, if I can pull it off.
> 
> This will be another practice run in preparation for processing my stock pot.
> 
> Just wanted to pull the thread back up on top of the heap so I dont have to dig to find it.
> 
> kadriver
> 
> 
> 
> 
> In that case all you need to do is subscribe to the topic. It's at the top of the page in the toolbar.
Click to expand...


Nice, I never knew subscriptions to threads were available, thank you.


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## cuchugold

This PGM itch is so addicting!. We are indeed blessed in this GRF that experienced, commercial, and skilled processors print all these procedures, tips and nuances on this and other ever evolving processes that can be considered trade secrets. As a dilettante I always enjoy reading these.


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## cuchugold

Re-reading this thread to reach 3 conclusions: Bromate use is not essential (replace with Chlorine sparging), removing all base metals substantially reduces hydrolisis supervision time, and done properly no flocculant is needed at all.

Q for Lou: Are these conclusions correct?.

Once again, my experience with this process is only a couple of Oz T at a time, and never repeated the exact same process once in the 7 times I've done it. I'll probably never do it again either.


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## Yggdrasil

I'm a bit reluctant to post in this thread, but due to relevance, I will do it anyway.
If someone find a better space for it, let me know and I'll ask the mods to move it.

Well here it is: 

As a preparation to make my own Sodium Chlorate and Sodium Bromate, I rediscovered this nice thread.
There is however a couple of questions that still hangs in the air.
Chuchugold made 3 "conclusions" he asked Lou to confirm.
As I see, the one about flocculant has been confirmed by Lou and others already earlier in the thread. 

The less Base Metals the less supervision and time is needed, seems logical, but is this statement accurate? 

Reading between the lines from Lou it seems that any sufficiently strong oxidizer present during hydrolizing will keep the PGMs in its correct oxidizing state and thus keep Platinum in solution while the others will come out as their hydrated dioxides.
Is this correct?
If so, does this mean that Sodium Chlorate can replace Sodium Bromate?
What about Potassium Chlorate/Bromate? 

Can an equilibrium complex of Sodium Chloride - Sodium Chlorate substitute Freechemists "preferred" method of Sodium Bromide - Sodium Bromate or is the Bromate the only way to go here?


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## Lou

Platinum is so cheap I've not bothered doing a hydrolysis in a long time. Even then, a lot of stuff I see has W, Mo, Re in it so hydrolysis only gets rid of cationic impurities and the other PGMs, to a certain extent anyway.


I never saw Cuchugold question or I would have answered him. As when selecting any procedure, the better part of valor is knowing when the hell to jump ship and do something else.

1. Less base metals means less hold up of platinum in the hydroxides produced by the process. By hold up, I mean you can rinse a lot of assay off but you'll still have Pt in the filter cake. Ordinarily the hydrolysis is like a finishing step done upon the "refinery" Pt sponge made from the precipitation of a salt. It's nice in that in gets rid of PGMs (iridium is hard to remove) and cationic base metals at the same time.
2. The reason why bromate is used is manifold...it raises pH slow and gives more defined easily filtered hydroxides, it removes Ru as RuO4 (heads up fellas!), it also doesn't have that really annoying *** tendency that chlorate has to make chlorine dioxide and y'know, explode or pop. I hate chlorate for that reason. Chlorine gas and (dilute) caustic is the best to use if you're doing hydrolysis on the cheap and have the setup to handle chlorine safely. 
3. Don't use potassium anything with platinum unless you want a K2PtCl6 precipitation and other weird crap as the pH goes up.


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## Yggdrasil

Thanks Lou.
Enlightening as always


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## orvi

Hi
Maybe trivial question to ask... But:

Gilchrist in his original publication describes that pH is measured by series of acid-base indicators (if i remember correctly), precisely describing the slightest color changes.

Solutions of PGMs as chlorides are extraordinarily colored. Mainly in acid and near-neutral pH range, it is difficult to measure pH of these solutions using pH paper strips. I was wondering how experienced guys here determine the pH of the solution precisely.
I have a good pile of various acid-base indicators from prehistoric ages in the lab  but missing some that Gilchrist mentioned in his paper.
Is there some trick how to use classic pH paper strips, or you use some specialized strips ? I also have a pH meter in hand, but it does not feel right to test the solution of precious metals (acidic on the start of hydrolysis) with some electrode meter (plating/corroding/deposition of metals on the sensor messing it up). 
Maybe it could be sufficient for me to know how to reach pH 7,5 (and be certain that it is pH 7,5), if there are some specialized methods used in industry, which couldn´t be passed to public


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## goldandsilver123

I've the same question, what's the proper pH - ORP probe for many specific solutions.

I never spent much time searching for this, but when I measure the pH of concentrated Pt solutions it's clearly visible that Pt is precipitating in the small fiber connection of the probe. I try to limit this by measuring quickly and DI washing after.



It's been quite a while after my graduation, so maybe I’m wrong, but I think it's possible to change the probe electrolyte from KCl to NaCl, probably it will have an offset, but should be usable. Never had time to try this.



Ammonia solutions are another problem, they dissolve the AgCl over the silver electrode and ruin the probe.



And I'm still searching for a probe designed to be immersed in solution 24/7, for the fume scrubber.


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