Developer Preservative--Minimum Quantum

Is there an accepted minimum quantity of sodium sulfite or other chemical to serve as preservative in a black and white developer?

i've used 35g/L with metol 6.5g/L with no noticable oxidation for around 6 months as an 'A' Bath of a developer. hope this helps.

There Is No Accepted Minimum

lensmagic said:

Is there an accepted minimum quantity of sodium sulfite
or other chemical to serve as preservative in a black and
white developer?

Click to expand...

A specific minimum for preservative purposes will depend
upon how the developer is used. If the developer is
prepared just prior to use and used one-shot as
little as 2 - 3 grams per liter may do. Dan

The amount will vary based on pH and developing agents used. It will also vary with respect to the effect you wish from the Sulfite ion. At high levels, it acts as a preservative and silver halide solvent as in D76. It has less effect with phenidone than with HQ. So the rane can be from 2g/l to 100g/l depending. Its effectiveness with HQ goes down to some extent with increases in pH.

Just BTW, the usable range in a color developer is vastly different, ranging from about 0.5g/l to about 10g/l.

PE

I once made an experiment to see in phenidone/ascorbate developer which agent lasts longest.
2 500ml cylinders ,call them A and B, were filled with PC-TEA 1:50 and left open to the air.After 14 days there was still some blackening of film leader,after 21 days none. The solutions went dark orange brown.
After 21 days phenidone equal to the amount originally present was added to A and an exposed film developed for the recommended time.It came out blank.
Also after 21 days sodium ascorbate to give ascorbate equal to the amount originally present was added to B and an exposed film developed for the recommended time.The film came out only slightly less developed than with PC-TEA 1:50.
In this experiment all the ascorbate was oxidized first, the phenidone survived virtually unchanged.

Alan, this is correct. However, remember that in 500 ml cylinders the surface to volume ration is not the same as for a tank or tray. Therefore the time factor is off by a considerable margin based on real conditions.

PE