From: Alan Greene (hobbyhorsedada@hotmail.com)
Date: 10/26/02-05:41:28 PM Z
Here's an example from the historical literature:
Jones, Encyclopedia of Photography (Arno reprint, 1911 ed.), under the
heading, "ferric ammonio-citrate," lists brown ferric ammonium citrate as
having a molecular weight of 2.030, and green ferric ammonium citrate as
having a molecular weight of 1.956; from this, I would infer that the two
are pretty much interchangeable.
Judging from the tone of the encyclopedia article, it would seem that brown
ferric ammonium citrate was more commonly used in 1911, but that green
ammonium citrate had recently been shown to be more advantageous, as evinced
from remarks stating that ". . . [green ferric ammonium citrate] gives much
more sensitive papers with purer whites than does the brown salt."
Hope this helps,
Alan Greene
>From: Richard Urmonas <rurmonas@senet.com.au>
>Reply-To: alt-photo-process-l@sask.usask.ca
>To: alt-photo-process-l@sask.usask.ca
>Subject: Vandyke formula using brown citrate
>Date: Sat, 26 Oct 2002 18:18:40 +0930
>
>Does anyone know of a vandyke formula using brown ferric ammonium citrate?
>Or can someone estimate a ration of green to brown citrate for the standard
>formula ?
>
>Richard
>---
>Richard Urmonas
>rurmonas@senet.com.au
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