[alt-photo] Ferric ammonium citrate (fwd)
alt.list at albertonovo.it
Tue Mar 6 15:30:06 GMT 2012
I have received a reply from Mike Ware off-list, and whith his permission I
forward it and the further comments.
---------- Messaggio inoltrato ----------
I noticed your enquiry on the Alt Proc List, and since you seem not to have
received an adequate answer I thought I would send my greetings and what
information I have:
I have the second English edition of Clerc on my shelves (1937), and a
footnote on p.405 gives the formulae as (you will know where to subscript
brown: (C6H5O7)2H2Fe2(OH)3)(NH4). 3H2O
As you will know, these differ somewhat from the formulae given by Valenta
(see p.157 of my book 'Cyanotype').
My third English edition of Clerc (1954) does not give any formulae at all!
With all good wishes,
Dr Mike Ware
20 Bath Road
+44 (0)1298 78604
mike at mikeware.co.uk
tank you so much! These information are what I exactly was looking for.
The green form looks like 2(Fe Citrate) + NH4 citrate, but the brown looks
May I forward your reply to the List?
Certainly forward it if you wish. You might add that the 'brown' formula
could be cast in the more rational form
Fe Citrate + (NH4)H2 Citrate + Fe(OH)3 + 3H2O
but of course these formulations tell us nothing about the structure of
these substances. The only modern structural chemistry I have come across is
in Inorganic Chemistry, 33, (1994), 5161, where the iron (III)citrate
complex anions are dimeric: [Fe2(C6H4O7)2(H2O)2]2- and [Fe2(C6H5O7)3]3-
which may be the photoactive dimeric species in solution.
> You might add that the 'brown' formula could be cast in the more rational form
> Fe Citrate + (NH4)H2 Citrate + Fe(OH)3 + 3H2O
I have the suspicion that these are not true formulae but the main
components used to form the green and the brown form. Or, alternatively (for
the brown form), what would have formed adding:
2 H3Citrate + 2 Fe(OH)3 + NH3
I know that it should be NH4OH, but NH3 keeps the resulting H2O =3 and not
I don't know what was the stoichiometry in 1930...
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