[pure-silver] Re: D-76 and variations
- From: "John Black" <jblack@xxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Mon, 28 Nov 2005 13:26:22 -0500
The problem with the rise in pH of D-76 with time is due to the
oxidation of hydroquinone. This is a fairly complex reaction in which
OH- ions are produced. It has nothing to due with either carbonates or
borax.
Oh.... other than buffering it, what was done about the pH problem with
storage? If hydroquinone oxidizes, is it still photographically active? I
could have sworn that there was an old formula or variation of D76 that had
carbonate in it.
Pure Na carbonate solutions are quite alkaline but not of a long term pH
stability. There seems to be an interaction between CO2 in the air and
carbonate ion, or so I've been told. In paper developers that use
carbonate, a rise in pH is not noticeable activitywise.
JB
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