[pure-silver] Re: Chemical substitution A CORRECTION!
----- Original Message ----- From: "BOB KISS" <bobkiss@xxxxxxxxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, April 28, 2007 6:44 PM
Subject: [pure-silver] Re: Chemical substitution A CORRECTION! 



DEAR RICHARD,
Just one favor...when you come out from under the bed, PLEASE tell me how much Sodium Citrate I should add per liter along with the other reagents to make stock solution of Hypo Clearing Agent. I want to correct 
my formula.
CHEERS!
BOB
I don't know. The only _authentic_ formula I have is the one in the patent which does not include Sodium Citrate only EDTA. The amount of citrate by weight listed in the Kodak MSDS is the same as the EDTA but what is listed is a 5:1 _range_ not a specific amount. I suspect the exact amount is not critical and I would try it at the same strength as the EDTA namely 2.5 grams/liter for the concentrate or 0.5 grams/liter if you mix working solution directly.
I have since discovered a bunch of old correspondence stored on a Zip disc including some from Doug Nishimura at IPI on permanance. I am going through this stuff to see what is relevant. For instance, he contradicts a statement made somewhere in the Kodak paper on wash aids, namely that the diffusion rate of gelatin increases with swelling where the Kodak paper speaks of minimising the swelling to make the diffusion path as short as possible. This is simply beyond my chemical knowledge. Doug Nishimura is a Phd chemist directly involved with photographic chemistry so I give considerable weight to anything he says. 

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx


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