# Reactivity of PGMs sponge versus black



## skippy (Mar 23, 2010)

I'm wondering if anybody has any anecdotes about the reactivity of PGM sponges versus PGM blacks to the usual acids - IE how much faster is it to dissolve platinum black versus platinum sponge.


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## Lino1406 (Mar 26, 2010)

sponge reactivity= black reactivity


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## Lou (Mar 26, 2010)

I disagree with Lino. Platinum black will dissolve quicker than platinum sponge. This is true for the rest of them as well. Metal blacks are likely to cause problems, so I suggest members here avoid them like the plague.


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## Lino1406 (Mar 27, 2010)

Thanks Lou. Please correct me if I'm wrong, Do you
say also that they dissolve differently or just the rate
is different?


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## Irons (Mar 27, 2010)

I think it all depends on particle size.


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## Lino1406 (Mar 28, 2010)

If so
Black particle size = ? angstrum
Sponge particle size = ? angstrum


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## Irons (Mar 28, 2010)

Lino1406 said:


> If so
> Black particle size = ? angstrum
> Sponge particle size = ? angstrum



Black particle and sponge are two names for the same thing. Surface area for a given quantity is probably a more accurate measure. More surface area, the faster the reaction given that other parameters remain constant (which never happens) since greater reactivity = greater delta T= faster reaction.


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## skippy (Mar 28, 2010)

Hmmm, interesting, so the sponge is basically an aglomerate of the black?
I asked the question in the first place because I read an article about reacting platinum sponge with iodine, and I wondered if the long (several days) reaction time specified would differ for platinum black. I guess the answer is yes, no, sometimes and maybe :lol: !


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## Lou (Mar 29, 2010)

Arik,

I don't know the mean diameters off the top of my head--in any case, it would be variable depending on reducing agent, concentration, and the temperature at which it is reduced.


And Skippy, I need to get ahold of you--I have *no* excuse for it.


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