[pure-silver] Re: Chemical substitution A CORRECTION!


On Apr 29, 2007, at 8:30 AM, Richard Knoppow wrote:
The target pH of Kodak wash aid is 7.0. The formula given in the patent is: 
Sodium Sulfite                20 grams
Sodium Bisulfite               5 grams
EDTA Na4                      0.5 grams
Water to make                  1 liter
Working solution.
The MSDS for the commercial product shows that it also contains Sodium Citrate in an amount similar to the EDTA Na4 but, of course, does not give the actual amount of any of the ingredients, only ranges. 


The patent is USP 2,860,978


Snipping
The above formula may have been the best when the '978 patent was filed. Later, they may have found out that the addition of citric acid/citrate salts (probably as an additional chelating agent rather than pH buffer) had added benefits. 

Howard
=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your 
account (the same e-mail address and password you set-up when you subscribed,) 
and unsubscribe from there.

Other related posts: