Eric Neilsen (e.neilsen@worldnet.att.net)
Tue, 11 May 1999 10:55:29 -0500
While I applaud all the efforts to make the coating solutions that we use in
the making of platinum and palladium prints, either with traditional or with
the ammonium systems of Ware/Malde or Zia(Sullivan/Weese), I must make
several corrections to Jeffreys'' formula weights and equations.
"Jeffrey D. Mathias" wrote:
>
> For the Ziatype variation, Ferric Ammonium Oxalate is used as the
> sensitizer with a basic reaction as follows:
>
> 3[(NH4)Fe2(C2O4)3+3H2O] =(via exposure)= 6Fe(C2O4) + 3(C2O4) + 3NH4
> (or this is attached to something) + 9H2O
This is an incorrect equation. The formula for Ammonium Ferric Oxalate is
(NH4)Fe(C2O4)3.3H2O. Providing a one to one creation of ferric to ferrous
ions unlike traditional ferric that has a formula (as best as can be tested,
or least the one that shows up in writing as) Fe2(C2O4)3.5H
Traditional:
Fe2(C2O4)3 + light (UV) = 2FeC2O4 + 2CO2 (gas)
and with Platinum
2FeC2O4 + K2C2O4 + K2PtCl4 ----> Fe2(C2O4)3 + Pt + 4KCl
Ammonium:
2[Fe(C2O4)3]3- ------------- 2[Fe(C2O4)2]2- + (C2O4)2- + 2CO2
2[Fe(C2O4)2]2- (PdCl)4- + 2(C2O4)2- ----- Pd + 2[Fe(C2O4)4]2- +
4Cl-
(as best as I can reproduce from my notes)
a 2 to 1 relationship between Ammonium Ferric Oxalate and the metal salt,
which I think is why Mr. Ware uses 1.4M AFO and approximately .7 M metal
salts in his system. Granted we are talking Zia...
>
>
> The basic Pt/Pd process reaction with Lithium substituted is:
> 6Fe(C2O4) + 3Li2PdCl4 = 2Fe2(C2O4)3 + 2(FeCl3) + 6LiCl + 3Pd
>
> To balance this, each (NH4)3Fe2(C2O4)3 will require <ONE> Li2PdCl4
> <<<<<<<<<<<<<
>
But to do that, you'll need two AFO
>
> Looking up the molecular weights of the ingredients:
> FW of (NH4)Fe2(C2O4)3+3(H2O) is 447.83 <<<<<<<<<<<<<<
> FW of Li2PdCl4 is 262.09
> FW of LiCl is 42.39
> FW of PdCl2 is 177.31
>
FW AFO (ammonium ferric oxalate) is 430.85
> IS THERE A CHEMIST IN THE HOUSE?
I'll second that, this can get thick.
Best,
EJ Neilsen
-- Eric J. Neilsen 4101 Commerce Street, Suite #9 Dallas, TX 75226 214-827-8301 http://home.att.net/~e.neilsen
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