[pure-silver] Re: 'Ripening' procedure for developer?
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 4 May 2007 15:38:28 -0700
----- Original Message -----
From: "BOB KISS" <bobkiss@xxxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, May 04, 2007 2:29 PM
Subject: [pure-silver] Re: 'Ripening' procedure for
developer?
CALLING ALL CHEMISTS,
Is sodium metaborate the same as Borax which is listed as
sodium
borate? Is this yet another situation like Metabisulfite
and bisulfite?
CHEERS!
BOB
Borax is a different chemical from Sodium Metaborate AKA
Kodalk. The use of Sodium Metaborate in a developer results
in a higher pH than if Borax is used making the developer
more active. Kodak published a formula for D-76 with Kodalk
around the time that it was publishing a number of formulae
using it. Sometime in the mid or late 1930's a Kodak
scientist discovered a method of manufacturing Sodium
Metaborate economically and the company began to use it in a
number of formulas. Metaborate, in general, has a pH between
Borax and Carbonate. It also has the advantage over
Carbonate that it does not evolve gas when subjected to an
acid.
(USP 1,976,299 Harold D. Russell, 1934)
Kodalk is Sodium Metaborate, tetrahydrate but the method
of specifying the hydration was changed sometime in the past
so its frequently listed as the Octahydrate, In any case,
both are the same substance. The patent above refers to the
Octahydrate. See Ryuji's article for details.
The idea of the Kodalk version of D-76 (sometimes listed
at DK-76) was to take advantage of the supposedly greater
buffering ability of Metaborate but it doesn't work well so
the Borax-Boric Acid version is preferred. I once saw a very
old MSDS for packaged D-76 indicating it contained
Metaborate but was never able to find it again. In any case,
the packaged form of D-76 seems to have used the Borax-Boric
Acid formula for at least the last twenty-five years.
Sodium Metaborate can be made in solution by using Borax
and Sodium Hydroxide in the correct proportions. Those on
Ryuji Suzuki's Silver Grain site are: In order to make 1.0g
sodium metaborate tetrahydrate, mix 0.692g borax and 0.145g
sodium hydroxide. That is, 0.692 grams of Borax and 0.145
grams of Sodium Hydroxide when mixed in water are the
equivalent of 1.0 gram of Sodium Metaborate Tetrahydrate or
Kodalk.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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