A 50/50 solution at what concentration? Water and Wastewater,
that could parts per million and not very many parts. A 1% solution
is 10,000 parts per million. That's not milligrams per liter that's grams
Bicarbonate of soda is a weak alkali and 8.2 IS weak. Dan
Originally Posted by jim appleyard
Here's the D-23C recipe I experimented with years ago. The first version is just ordinary D-23 with Vitamin C added.
Metol-- 7.5g or 2 1/8 tsp.
Sulfite-- 100g or 4tsp. + 1tsp.
Ascorbic acid-- 1 g or 1/4 tsp.
In those days, before tabular grain films, I was mostly using HP5+ and FP4+. Try a starting time around 7 minutes at 70 degrees. You'll have to adjust that no doubt to find what's right for your film choice.
I found that the addition of the Vitamin C just made the developer more active.
Later, I experimented with decreasing the amount of sulfite to about 20g and it still worked fine, perhaps with some adjustment to times, though I don't remember clearly, and in those days of my omniscient youth, I didn't always need to write down notes to myself.
Since then, Pat Gainer has demonstrated that in Phenidone/C developers, sulfite is totally unnecessary. I don't know whether this holds true with Metol-based developers or not. Pat might want to chime in here and set us straight.
I also modified the replenisher D-25R by the addition of 1/4 tsp. Vitamin C as well and replenished as the D-23 instructions recommend. That worked well too.
I haven't used this for years, since I've switched to Phenidone/C exclusively now, but I remember being very satisfied with the quality of the negs I got.
The main principle, of course, is that Vitamin C is superaddititive with Metol (or vice versa) just as it is with Phenidone.
Kirk is referring to a carbonate buffer system in which equal concentrations (in molar terms) of carbonate and bicarbonate give a pH of 8.3. It does not matter what the concentration of the two species are, as long as they are equal. This is one of the properties of buffer systems. They can be diluted and maintain their pH (although not their buffering "capacity").
Originally Posted by dancqu
Incidentally, I believe that the carbonate-bicarbonate system is what the body uses to regulate the pH of blood. It is intimately tied to the regulation of CO2 in the blood, etc.
No need for sulfite in PC or MC. You may feel a need for it for some other reason, but I doubt you'll find any significant improvement in grain. Now, with PQ or MQ, you need a little sulfite for maximum synergism. Without it, PQ or MQ make staining developers somewhat akin to catechol but different color.
Originally Posted by Maine-iac
The amount you need with hydroquinone is only about the same weight as the hydroquinone. Not enough to have any effect on grain.
Sorry Dan, I was talking about a ratio of 50/50, not some actual, particular concentration.
Originally Posted by dancqu
Water and wastewater does range from very low parts per million to percentage concentrations. The same principles apply to both situation.
"Bicarbonate of soda is a weak alkali and 8.2 IS weak."
Weak what - alkalinity? pH?
You seems to not understand some fundemental concepts of pH and alkalinity with that statement. It all depends on the concentrations.
The alkalinity of a water is an meaurement of the acid-neutralizing capacity of the water. You can easily make a solution that has a pH of 6 that has thousands of times more alkalinity and is a much stronger buffer than a solution that has pH of 13.
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