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>Date: Thu, 15 Jan 1998 12:00:05 -0500
>To: Sandy King <hubcap.clemson.edu@CLEMSON.EDU>
>From: Sil Horwitz <silh@iag.net>
>Subject: Re: Sodium Ferrocyanide
>In-Reply-To: <l03130301b0e33df9086c@[204.189.110.108]>
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>At 12:18 AM 1998/01/15 -0400, you wrote:
>>I have a large bottle of Sodium Ferrocyanide which was mistakenly sent to
>>me in place of Potassium Ferrocyanide. Does Sodium Ferrocyanide have any
>>applications in the alternative processes (or in regular photographoc
>>processing for that matter).
>
>Why did you want the ferrocyanide in the first place? (Just curious.) I
>don't know of any use for it, but I'm sure if you dig back far enough
>someone used it for something! Most of the alt photo processes which use
>the ferricyanide depend on the action of the ferri- ion as it converts to
>the ferro- form. As to sodium vs potassium, in most formulas where the
>potassium is specified, it's because of the greater solubility of the
>potassium salts or the greater availability of certain potassium compounds.
>Also, in most formulas, there is enough slack that the minor weight
>difference (sodium is heavier than potassium, but not by much) isn't
critical.
>
>Incidently, though the ferrocyanide (in spite of its name) is not toxic
>like cyanide compounds (the ferro- ion binds to the cyano- ion and prevents
>the cyano- from reacting), either adding acid or heating above 400C will
>release the very poisonous cyanide gas. An interesting fact: combining this
>compound with an iron salt makes Prussian blue pigment; this is exactly
>what happens in cyanotypes, where the ferri- is changed by light to the
>ferro- form, which creates the Prussian blue of the image.
>
><<sil>>
><silh@iag.net>
><webmaster@psa-photo.org>
>Sil Horwitz, FPSA
>Technical Editor, PSA Journal
>check out <http://www.psa-photo.org>
>
>