[pure-silver] Re: Adding Sodium Sulfite to Sodium Thiosufale.
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sat, 2 Apr 2011 16:10:01 -0700
----- Original Message -----
From: "Gerald Koch" <gerald.koch@xxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, April 02, 2011 3:29 PM
Subject: [pure-silver] Re: Adding Sodium Sulfite to Sodium
Thiosufale.
Sodium sulfite is not needed unless that hypo solution is
acidified in some
manner. If you don't use an acid stop bath you won't need
it. When acid is
added to a sodium thiosulfite solution colloidal sufur is
produced. The sulfite
ions combine with the sulfur to regenerate thiosulfate ions.
There is a classic chemistry demonstration called "the
setting sun." A beam of
light from a slide projector is passed through a thiosulfite
solution onto a
screen. It looks like the sun. Then, with stirring, a small
amount of acid is
added. The "sun" becomes more and more reddish in appearence
as colloidal
sulfur scatters the light. It looks like the sun is setting.
This scattering
is of course exactly what happens to the real sun as it
reaches the horizon.
The light must pass through more of the atmosphere with
greater scattering of
the shorter wavelengths.
Jerry
The sulfite will also tend to preserve the thiosulfate
from oxidation from the air. A common non-hardening fixing
bath will have about 5 grams/liter of sulfite in it. The
usual acid bath has about 15 grams per liter. The small
amount of sulfite also prevents staining from carried over
developer, which in a non-acid bath, may remain active for a
time.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your
account (the same e-mail address and password you set-up when you subscribed,)
and unsubscribe from there.
Other related posts:
