John Melanson (john@audiologic.com)
Tue, 27 Jul 1999 10:29:55 -0600
Now we have really moved away from "what kind of photographer are you?" to
tech propeller head nirvana.
In solution, borate, metaborate etc. are a mixure of borates (a polymer form
of BO3 and BO4 is suspected). That's why they are such good buffers. So in
solution there is no such thing as "pure metaborate". The solution is
equivalent within your ablility to measure, use pure chems, etc.
"The fact that certain complex borates can be precipitaded or crystalized
from solution does not constitute evidence for the existance of such anions
in solution ..... " (Cotton & Wilkinson, "Advanced inorganic chemistry").
In english, borax, metaborate, etc are only well defined when crystalized.
The solution doesn't know how it was made.
The mixture of borax and NaOH can be crystalized to "pure" metaborate. If a
small excess of NaOH is used, no other borate form is crystalized.
By the way, I have heard that Kodalk is not really sodium metaborate, but a
mixture. I don't know if that's true, or just Kodak marketing.
Brew your own with a clear and frugal conscience.
John
> -----Original Message-----
> From: Sil Horwitz [mailto:silh@iag.net]
> Sent: Tuesday, July 27, 1999 8:58 AM
> To: alt-photo-process-l@sask.usask.ca
> Subject: Re: sodium metaborate, to make?
>
>
> At 1999/07/27 08:38 AM +0100, you wrote:
>
> >Thanks for the info on sodium metaborate. I found the following
> info in the
> >Focal Encyclopaedia of Photography. Sodium metaborate can be made in
> >solution by mixing 1 part sod hydroxide with 5 parts borax, both being
> >dissolved in water. This is equivalent to 7 parts sodium metaborate.
>
> "Equivalent" - probably. Pure sodium metaborate - no. It will be
> a mixture of
> borates which is OK if it works in your application.
>
>
> Sil Horwitz, FPSA
> Technical Editor, PSA Journal
> silh@iag.net
> silh@earthlink.net
> Visit http://www.psa-photo.org/
> Personal page: http://home.earthlink.net/~silh/
>
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