[alt-photo] Re: Clerc and am fe citrate

[Peter Friedrichsen]

Hi Don,

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.

Peter Friedrichsen

At 03:19 PM 06/03/2012, you wrote:
>Peter
>
>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
>
>Don Sweet
>
>
>----- 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:
> >
>http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm?fr=184.1296
> >
> > 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
> > >_______________________________________________
> > >Alt-photo-process-list | http://altphotolist.org/listinfo
> >
> > _______________________________________________
> > Alt-photo-process-list | http://altphotolist.org/listinfo
>
>_______________________________________________
>Alt-photo-process-list | http://altphotolist.org/listinfo