[pure-silver] Microdol-X Patent

U.S.Patent No. 2,466,423 issued to Richard Henn and John I. Crabtree and assigned to Eastman Kodak is for fine grain developers containing Chlorides as the fine grain agent. This is the mechanism used for Kodak MIcrodol-X and Ilford Perceptol. While it is not possible to know of any of the example formulae given in the patent represent the actual packaged product they at least give a better clue as to its composition than the MSDS. While patents are legal rather than scientific or technical papers the patent does include some discussion about the action of the addition. 
     An example of the formulae is the following:
Metol 5.0 grams 
Sodium Sulfite, anhydrous            100.0 grams
Ethylene diamine sulfate                 12.0 grams
Sodium Metaborate                           4.0 grams
Potassium bromide                            0.25 gram
Sodium chloride                                20.0 grams
Water to 1.0 liter
Another interesting Kodak patent covering the use of chlorides as fine grain agents is USP 2,053,516. This shows the addition of Ammonium chloride to several formulae including D-76. The Henn patent, above, has reference to this and has some criticisim of the use of Ammonium salts.
I also found a number of other Kodak patents covering chealating agents and the treatment of various alkalies to make them more stable in packaged products. Kodak seems to have done a lot of research on making single powder packages, perhaps they are more economical than having to split the ingredients into two or more separate parts. 

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Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx



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