Process Equations

DOP - Ferric Oxalate POP - Ammonium Ferric Oxalate

The process equations help provide an expression of the chemical reactions and an expectation of the materials necessary to provide for predicted outcomes.  Unfortunately, the reactions and these equations are not fully understood.  Future research may provide better understanding and insight as to the Pt/Pd process.

There are two primary processes to consider:
DOP - Develop Out Process employing the sensitizer Ferric Oxalate
POP - Printing Out Process employing the sensitizer Ammonium Ferric Oxalate
Current understanding seems to indicate that the metal salts behave similarly and each sensitizer gets to the same outcome by a different route.

The most useful information from the process equations for the process as described in this guide are the ratios of metal salts to sensitizer required.  The ratios have been discerned empirically in the Empirical Verification of Process Equations.

Process Equations for Ferric Oxalate:

The sensitizer reacts to light, heat, or time as follows:

3Fe₂(C₂O₄)3•6H₂O  >exposure>  6Fe(C₂O₄) + 3(C₂O₄) + 6H₂O

The metals are released by what is known as Brewster's Reaction described by Berkeley's equation:

6Fe(C₂O₄) + 3K₂PtCl₄ => 2Fe₂(C₂O₄)3 + 2(FeCl₃) + 6KCl + 3Pt

The same occurs for Palladium:

6Fe(C₂O₄) + 3Na₂PdCl₄ => 2Fe₂(C₂O₄)3 + 2(FeCl₃) + 6NaCl + 3Pd
or
6Fe(C₂O₄) + 3K₂PdCl₄ => 2Fe₂(C₂O₄)3 + 2(FeCl₃) + 6KCl + 3Pd
or
6Fe(C₂O₄) + 3Li₂PdCl₄ => 2Fe₂(C₂O₄)3 + 2(FeCl₃) + 6LiCl + 3Pd
etc.

Every three Fe₂(C₂O₄)3 will pair with three K₂PtCl₄  or Na₂PdCl₄  or K₂PdCl₄   or Li₂PdCl₄, a ratio of one-to-one (1 metal salt for 1 sensitizer).

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Process Equations for Ammonium Ferric Oxalate:

The sensitizer is thought to react generally as follows:

(NH₄)3Fe(C₂O₄)3•3H₂O  >exposure>  Fe(C₂O₄)2 + 3(NH₄) + 3H₂O + 2CO₂

Some of the (C₂O₄) is changed into the 2CO₂ gas as suggested by Mike Ware.
For a description of the reactions by Mike Ware click here.

The basic process reaction for AFO with Lithium is thought to be:

3Fe(C₂O₄)2 + 3Li₂PdCl₄ + 3(NH₄) + 3H₂O  =>
(NH₄)3Fe(C₂O₄)3•3H₂O + 2(FeCl₃) + 6LiCl + 3Pd + 3(C₂O₄)

Or other metallic salts could be substituted.

Every three sensitizer molecules will pair with three metallic double salt molecules, a one-to-one ratio (1 metal salt for 1 sensitizer).

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