Re: Dichromate in Developer for Palladium (was Re: paper test data for palladium)
richard Sullivan (richsul@roadrunner.com)
Sun, 18 Feb 1996 10:26:41 -0700
>I'm interested - and not a little surprised - to learn of the use of an
>oxalate developer for platinum/palladium which contains dichromate to
>'control' contrast.
>
>The reaction between these two ions is well-known to inorganic chemistry,
>and is indeed one of the standard methods for preparing a whole range of
>oxalato- complexes of Chromium(III). Admittedly the lab preps entail
>heating, but this is just to speed up the process. I doubt that any
>solution containing the two will remain unaltered for very long, even at
>room temperature.
>
>Keith has just described one consequence:
>
>>KOx does not become
>>exhausted. I don't know about the dichromate. I have found some green
>>needle-like crystals in one of the bottles.
>
>This is, very probably, potassium tris-oxalatochromate(III): K3Cr(C2O4)3.3H2O
>
>The other consequence is that when the Cr(VI) of dichromate is thus reduced
>to Cr(III) it will cease to have a 'contrast enhancing' effect.
>
>Mike
Mike,
I am curious. I have heard of the chromium complexes formed with the
oxalates. Dick Arentz tried this a few years back and was told about them.
What about non-oxalate developers such as ammonium citrate, potassium
citrate, the acetates, etc, would they work with the chromates. Also Arentz
was told to use chromic acid instead of the chromates, presumably by someone
knowledgeable.
Dick Sullivan