From: Sil Horwitz (silh@earthlink.net)
Date: 04/22/00-09:21:12 PM Z
At 2000/04/23 03:10 AM +0100, Liam wrote:
>B. Ammonium sulphocyanide . 2 oz.
> Water to make . . 8.25 oz.
>C. Lead acetate . 1 oz.
> Boiling water to make .8.25 oz.
>
>A dense precipitate will settle. The bottle mast be well shaken each time
>any solution is required.
Wow! Lead acetate is very toxic, even in small quantities. In addition,
lead thiocyanate (old name: lead sulphocyanide) is about as insoluble a
compound as you can make, so that's what the precipitate will be, and of no
use whatsoever. Can't imagine what the purpose is, as lead is a gold killer
- why would you want to inhibit the toning and waste gold? There are more
modern, better formulas. In fact, in my experience it is better to do the
gold toning after a quick wash and prior to fixation and final wash.
Just curious: anyone reading this know specifically what the purpose of
precipitated lead thiocyanate is in this formula? You couldn't dispose of
this down the drain, either, what with all the restrictions on lead disposal!
Sil Horwitz, FPSA
Technical Editor, PSA Journal
teched@psa-photo.org
silh@earthlink.net
Visit http://www.psa-photo.org/
Personal page: http://home.earthlink.net/~silh/
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