Re: White precipitate

Sil Horwitz (silh@iag.net)
Sun, 22 Sep 1996 23:03:44 -0400

At 07:51 AM 960923 +1000, Jonathon Russell wrote:

>I have a material Safety Data Sheet in hand for Kodak Hypo Clearing
>Agent that list the percentage of EDTA at only 5% by weight. The main
>component is sodium sulfite: 80% by weight.I wonder if we are not
>"barking up the wrong tree" by concentrating on EDTA. Any thoughts from
>the list?

Basically, Hypo Clearing Agent (or Wash Accellerator) is sodium sulfite.
EDTA is a chelating agent, and is used in this formula mainly to prevent
precipitation of calcium sulfite resulting from hard water. As far as I can
determine, it EDTA is not a major ingredient in wash accellerators. There
are other formulas which use wetting agents, anti-foaming agents (to prevent
the wetting agent from bubbling), and other, sometimes proprietary, ingredients.

Again, EDTA is a chelating agent, a substance which prevents two or more
possible interacting ingredients from combining. It might (I haven't either
tried or tested it) have some usefulness in minimizing reaction from wash
effluents with possible active ingredients in the image.

Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net