Hi Brad,
I have followed that discussion, and I was under the impression that this "Kodak magic" just served to prevent the cross contamination of the materials during storage and transport. Maybe I'm wrong though.
Hans
The metol will not dissolve in the sulfite solution. There's special magic in the Kodak manufacturing process that makes it work.
Hi Brad,
I have followed that discussion, and I was under the impression that this "Kodak magic" just served to prevent the cross contamination of the materials during storage and transport. Maybe I'm wrong though.
Hans
I never do and to my opinion it makes no difference. I make my D-76H (Grant Haist formula, no hydroquinone) from raw chemicals, most of the time just enough to make developer for the film at hand, directly in a 1:1 solution and use it right away. Worst problem: cool it down sufficiently fast. I get consistent results after initial testing with 2-3 films with good tonescale and density on Tmax 400 as well as Tmax 100.
I wonder if one could dissolve all the chemicals in one batch instead of adding them one by one. Never tried. Anyone? Seems to be the case with the commercial available D-76 from Kodak.
Hans
Metol in solution is acidic and is not likely to oxidize
any more than it already has.
The earliest instructions I have seen, in Hardy & Perrin
"Principles of Optics", 1930, say to dissolve the Metol
in a small amount of water,
"... not likely to oxidize" is not the same as "will not oxidize"
Dissolved oxygen is elemental. Elemental uncombined oxygen
is a very strong oxidizer.
"... dissolve the Metol in a small amount of water ..."
Little water little dissolved oxygen. Dan
Does not the pH have an effect? Dissolved oxygen should tend toward basic, depending on what else is in there.
Dissolved oxygen is elemental. Elemental uncombined oxygen
is a very strong oxidizer.
....If the D76 is made from scratch everything dissolves in seconds and it can be made up with room temperature water........
I am guessing that D-76 is cheaper than ID-11 in you location.I add a pinch of S. Sulfite before the metol.
If the D76 is made from scratch everything dissolves in seconds and it can be made up with room temperature water.
I would prefer a two package formulation from Kodak, I think the single packet idea is to save Kodak money, and not to make my life any easier (though I guess if it saves Kodak money, it also saves me money).
Does not the pH have an effect?
My original post had nothing much to do with what the water would do to the Metol, dissolved air or not. It concerned the initial state of the Metol, which could be already partially oxidized. Sulfite does not, from what I have read in "The Theory of the Photographic Process", regenerate the Metol, but changes the oxidized portion to a form that does not inhibit development. If all the Metol were oxidized, it would be converted to a compound tht does not inhibit development, but there would be no development either. Ascorbic acid OTH was said to actually regenerate the Metol. This fact shows as if it were superadditivity in some cases. It is difficult or impossible to tell by performance whether a developer is a simple combination of Metol and ascorbate or a combination of Metol, hydroquinone and sulfite. Over the short term, Metol and sulfite is in that group, Metol and hydroquinone without sulfite are no better than Metol alone.Again, wrong. It is not "elemental". Dissolved oxygen is molecular oxygen, O2. That said, it is still an oxidizer. You will not find elemental oxygen around in nature, as it will react with another oxygen and from ozone. Look at electrolysis, you've just broken apart a water molecule, and the "elemental" oxygen rapidly forms diatomic, molecular oxygen.
(At very high temperatures, like >5000K, you can get dissociation of molecular oxygen, but not at any temps we are interested in.)
When air dissolves in water, the oxygen does not ionize. It simply dissolves. Same with nitrogen. They are both diatomic molecules and they do not ionize in water.
Think about it, guys. If oxygen did "decompose" and raise the pH of water, all of our oceans, rivers, and other natural bodies of water would eventually become caustic and nothing could live in them...
....Metol and hydroquinone without sulfite are no better than Metol alone.
Sodium sulfite has a preservative action on alkaline developer solutions and also acts to convert the quinone formed in the developing process by a 1,4-addition to hydroquinone-sulfonic acid.
The sulfonic acid has itself some developing power and, in the presence of sulfite, more than one equivalent of silver bromide can be produced for each equivalent of hydroquinone used in making up the developer.
Mr. Gainer,
You may find section 25-5 of the following interesting....
John D. Roberts and Marjorie C. Caserio
Basic Priciples of Organic Chemistry
(C) 1964, W.A. Benjamin, Inc.
Library of congress cat no. 64-16071
specifically:
In this kind of group, you can leave out the pejorative expression like "as you seem to thiink."
gainer said:Dissolved oxygen should tend toward basic, depending on what else is in there.
Mr. Gainer, You may find section 25-5 of the following
interesting....John D. Roberts and Marjorie C. Caserio
Basic Priciples of Organic Chemistry
(C) 1964, W.A. Benjamin, Inc.
I find it interesting. Do they go on to describe the action of the quinone in the absence of sulfite; an exponential increase in hydroquinone sulfonic acid? Dan
Mr. Gainer,
You may find section 25-5 of the following interesting....
John D. Roberts and Marjorie C. Caserio
Basic Priciples of Organic Chemistry
(C) 1964, W.A. Benjamin, Inc.
Library of congress cat no. 64-16071
specifically:
Nope. I should have left it as a question: "Does the pH have an effect?". It was either too late at night or too early in the morning. Those times are often simultaneous for me.No perjorative intended.
I was addressing what appeared to me to be your belief that dissolved oxygen would have an effect on pH.
Maybe you can clarify your statement then.
No, This section comes in the middle of a chapter on phenols
and quinones. Section 25-5 is short and sweet and focuses
on how hydroquinone works as a B&W film developer.
Another point of interest is the high mixing temperature, even while the Metol is in water alone. It may in fact be true that heating the water removes at least as much of the dissolved oxygen as the "pinch" of sulfite. The solubility of oxygen in water is approximately half at 71 C that it is at 20 C. Maybe we should use both belt and suspenders and heat the water as well as use the pinch of sulfite or ascorbate.
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