Sandy King (sanking@hubcap.clemson.edu)
Sat, 22 May 1999 16:16:46 -0400
Eduardo Benavidez wrote:
>Concerning your question about the use of potassium carbonate crystals,
>not anhydrous (the crystal form is said to give a slight bicarbonate
>buffer effect), this mean as a general rule, that when you use crystals,
>there is a chemical reaction wich produces BICARBONATE, wich plays the rol
>of BUFFER agent (i.e. maintaining the same developer activity during the
>whole developing time). Read about the buffering effect in The
>F.D.Cookbook.
>
>...and how might the same effect be gotten with the anhydrous variety?
Is the bicarbonate buffer agent that is said to be provided by the use of
potassium carbonate crystals meant to apply to the stock or working
solution? When I first read the directions for mixing the develper in The
Film Developing Cookbook, for some reason I assumed that the buffer agent
was to preserve the pH of the stock solution. So I guess the question is,
how stable is the pH of a 6-7% potassium carbonate solution?
The Film Developing Cookbooks recommends as an alternate to potassium
carbonate crystals the substitution of sodium metaborate at about 1.5X. Has
anyone tried this?
Sandy King
This archive was generated by hypermail 2.0b3 on Thu Oct 28 1999 - 21:39:34