On Tue, 10 Jan 1995, Shaw, Brian E. wrote:
> Not being a chemist, I find this rather perplexing. I like the idea of
> doing business with firms like Bostick & Sullivan in business, but is
there > really a difference between their's and a major chemical house's
Ferric > Oxalate? Luis and the group, can you provide a little more
insight into any > difference for Ferric Oxalate or any other chemical
that is used in > alternative processes. > > Thanks, > Brian
(shaw@courier3.aero.org) > I too find it perplexing but... When I was
first printing Kallitypes in the late 60's and early 70's I was able to
obtain a fine yellow powder grade of F.O. from Tri-Ess in Glendale Ca.
That source ended due to a fire at tri_ess and when they came back on line
their source had dried up. They then obtained some from as I remember
Eastern Chemical it was a greyish mess and only partially dissolved. I
also obtained some from the original "Elegant Images" It came in a sort of
wet lump and seemed to be mostly ferrous. Allan Newman related to me some
stories of taking days to dissolve F.O. that he obtained in the 60's. To
my knowledge there is no published formulas for making a powdered form of
ferric oxalate in the standard preparatory text, either Bauer or the
Handbook of Preparatory Chemistry. My own method which is trade secret
(not patented) was in some ways discovered by accident. We also add a very
small quantity of nitric acid to our f.o as a preservative. Nitric acid is
an oxidizer and evaporates from the emulsion in drying and in the tiny
quantity used, is reasonably benign to humans and the environment. The
nitric acid also seems to promote soluablility. Yes EDTA is a good
additive for enhancing soluability.
I suspect the problem lies in other companies trying to come up with a
good way to make it. First off, ferric oxalate is an unstable compound,
and that's precisely why we use it. A very weak force like light alters
it. Making unstable compounds is by it's nature a more difficult task.
Trying to dry a liquid ferric oxalate usually results in the larger
portion becoming ferrous in the process, thus a problem. Secondly, there
appears to be no other common use for the stuff, so it's not an issue
with the big chemical comapnies. Did, however, sell some to the UCLA
Dental School for some experiment a few years ago.
I guess things like this are what's keeping the cottage industry movement
moving.
Dick Sullivan
Bostick & Sullivan