[pure-silver] Re: Chemical substitution A CORRECTION!
- From: Howard Efner <hfefner@xxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Sun, 29 Apr 2007 21:35:24 -0600
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
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