Re: Conversion of K2ptcl4 to K2ptcl6

Philippe Monnoyer ()
Thu, 16 January 1997 5:29 AM

One of the benefits of the List however, is to go beyond the
>formulaic. Rather than just describing what happens when certain conditions
>are set up, to get to the "why", the science of it all.
>
My ears perk up a
>little more when the science comes along with it.
>
>I have made a ton of platinum and palladium salts in the last 15 years --
>well literally at least. I have done some testing along the way. I still say
>that K2PtCl6 will not produce black specks in a print. Something else may be
>going on. In every case we've been able to nail down, black specks have been
>caused by two things. Either ferrous metal contamination or on rare
>occassions the K2PtCl4 kicking out Pt metal. Making the K2PtCl4 is a tricky
>process. By its nature it is an unstable chemical, that's the plague all
>photographers have to live with, to be sensitive to light or work in light
>sensitive systems, they must be unstable. (The chemicals not the
>photographers.) I've seen batches from big name chemical companies that were
>embarassingly bad.
>
>I am interested in any other opinions in this issue.
>
>
>Dick Sullivan
>

Dick,

A lot of answers are in Inorganic Chemistry Books.
I completely agree with you, I think things are improved faster when you
understand henk.thijs@eurocontrol.be (or feel) why you change processing steps to get what you want.
Why do you want to get K2PtCl6 instead of using K2PtCl4 ? I would think you
loose some sensitivity with K2PtCl6 , am I right ? The ferrous oxalate you
form while exposing as a given number of electrons to reduce the platinum
ions. That number is proportional to the amount of light that you gave to
the layer. The difference between K2PtCl4 and K2PtCl6 is that they contain
respectively Pt2+ and Pt4+. To reduce Pt2+ to metallic black platinum, you
need 2 electrons from the ferrous oxalate. To reduce Pt4+ you need 4
electrons. So, for a given exposure, you will get twice the black reduced
platinum with K2PtCl4 vs K2PtCl6.
Does it match to your experiences ?

Philippe
_____________________________________________________________________________
Philippe MONNOYER
Ph.D. Student
Laboratoire de RMN
Facultes Universitaires Notre-Dame de la Paix
rue de Bruxelles, 61
B-5000 Namur
Belgium

Phone: +32 81 724601
Fax: +32 81 724530
Mail: Philippe.Monnoyer@fundp.ac.be

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