Re: Dichromate in Developer for Palladium

Mike Ware (mike@mikeware.demon.co.uk)
Tue, 20 Feb 1996 11:32:13 +0000

Dick Sullivan commented

>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.

In principle, dichromate will oxidise citrate and acetate as well - given
long enough. But the *rates* of these reactions will be slow. One can
probably get away with mixing dichromate with these organic acids/salts
over a timespan of minutes or hours at room temperature, but I wouldn't
trust such a mixture to remain substantially unchanged over days/weeks.

> Also Arentz
>was told to use chromic acid instead of the chromates, presumably by someone
>knowledgeable

The oxidising power of dichromate increases with higher acidity;
conversely, in alkali, dichromate is converted to chromate and its
oxidising power is greatly lessened.

Mike