[alt-photo] Re: Clerc and am fe citrate
pfriedrichsen at sympatico.ca
Fri Mar 9 02:53:53 GMT 2012
The green variety of ferric ammonium citrate is a somewhat muted
green (camouflage green!) either in solution or as dried scales or
powder so it seems that your green fac must have deteriorated. If
this is the case I suspect it is many years old or was exposed to
light, heat. I have some three year old solution which remains a nice
shade of green and tests free of any ferrous species. A little
potassium ferricyanide makes for a simple test for this reduced form
of iron. If the test is negative, then perhaps you do have the brown
form. I heard mention once that a wee bit of hydrogen peroxide can
re-oxidize ferrous but I have not tried this.
As far as attempting to change the brown variety to green? I made
some attempts along these lines but was not successful. You see, In
my first attempts to make green fac, I was always ending up with the
slower brown variety. I then attempted to adjust the quantities of
citrate and ammonia but it remained brown. I even left this for days
hoping it would re-speciate, but to no avail. Changing the order of
addition allowed me to produce the green variety.
Perhaps you will have better luck with conversion. Keep us posted.
At 03:19 PM 06/03/2012, you wrote:
>A couple of years ago you helpfully presented a method of making ferric
>ammonium citrate (green) starting from ferric chloride. I have been
>thinking of trying it, as all my fac (bought as "green" from reputable
>sources, but in some cases now a little old) is actually a dark khaki
>colour. Is that still "green" fac, or has it deteriorated at some point?
>On a related topic, I have read that brown fac can be converted to green by
>the addition of about 20% citric acid. Is that right?
>Thanks for your help
>----- Original Message -----
>From: "Peter Friedrichsen" <pfriedrichsen at sympatico.ca>
>To: "The alternative photographic processes mailing list"
><alt-photo-process-list at lists.altphotolist.org>
>Sent: Tuesday, March 06, 2012 11:09 AM
>Subject: [alt-photo] Re: Clerc and am fe citrate
> > Alberto,
> > I found this description some time ago. It doesn't tell you that the
> > green and brown forms depend not only on the composition, but also
> > how the starting chemicals are combined.
> > (1) Ferric ammonium citrate (iron (III) ammonium citrate, CAS Reg.
> > No. 1332-98-5) is a complex salt of undetermined structure composed
> > of 16.5 to 18.5 percent iron, approximately 9 percent ammonia, and 65
> > percent citric acid and occurs as reddish brown or garnet red scales
> > or granules or as a brownish-yellowish powder.
> > From:
> > Peter Friedrichsen
> > At 03:03 AM 04/03/2012, you wrote:
> > >I am looking for the chemical definition brown ammonium ferric
> > >citrate given by Clerc. I remember a footnote in:
> > >Clerc, L.P. (1950) "La Technique Photographique"
> > >5th Ed, tome II, Publications photographiques et cinematographiques
> > >Paul Montel, Paris V, 1950, pp.816-817
> > >I have had the oppportunity of taking some notes about the empirical
> > >formula of the green form, but unfortunately I did not save the
> > >information about the brown one.
> > >Now I nave not the opportunity to look at Clerc anymore. May you help me?
> > >Alberto
> > >www.grupponamias.com
> > >www.alternativephotography.com/wp/photographers/rodolfo-namias-group
> > >_______________________________________________
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