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Accelerator (alkali) substitution problem

lensmagic

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This is to all you inorganic chemists out there . . . .

A certain film developer has two ingredients: a developing agent and sodium sulfite, which serves as both preservative and accelerator.

One liter of the stock solution contains the developing agent and 100 grams of sodium sulfite. Nothing more. [Britons may wish to call it sodium sulphite.]

I want to create a new formula. The only change would be to cut the amount of sulfite in half, to 50 grams per liter of stock solution. How much sodium carbonate (monohydrate) would I need to add to a get a liter of stock solution with a pH equal to that of the original formulation?
 
A D-23 Type?


Likely the ph at 50 grams will be very nearly or the same
as with 100 grams. Buffer capacity will be reduced
though possibly not so much as to be noticeable.
Which and how much developer agent? Dan
 
dancqu said:
Likely the ph at 50 grams will be very nearly or the same
as with 100 grams. Buffer capacity will be reduced
though possibly not so much as to be noticeable.
Which and how much developer agent? Dan
Click to expand...

Metol (Elon) @ 5 grams per liter working solution.
 
the pH of D-23 is about 8, maybe even less. If you want to add something that will buffer the pH of the solution, you might want to try sodium carbonate - baking soda. It has a pH of about 7.5.
 
Kirk Keyes said:
the pH of D-23 is about 8, maybe even less. If you want to add something that will buffer the pH of the solution, you might want to try sodium carbonate - baking soda. It has a pH of about 7.5.
Click to expand...
**********
Baking soda is sodium BIcarbonate.
 
Agfa 14 calls for 1.2 gms sodium carbonate mono-hydrate, with 4.5 gms metol and 85 gms sodium sulfite. But is also specifies some potassium bromide as a restrainer.

Can't you get pretty much what you want just by diluting d-23 1:1?

Or just using DK-25R replenisher diluted 1:1?
 
Try the 1927 Kodak (there was a url link here which no longer exists) that the Research labs published in 1927 and add some Borax.

These formulae were around well before Kodak came up with D23, Hans Windisch recommended the following developer in "Die Neu Foto Schule"

Metol 2.5 g
Sodium Sulphite (anhyd) 50 g
Water to 1 litre

Ian
 
*******
Ian, do you think the difference in metol in this Windisch formula would make this developer significantly different from diluting D23 1:1?
 
Not really particularly with modern film, it's just an older formula than D23 and there were plenty of others. It may give slightly finer grain, which would have been more noticeable with pre-WWII emulsions, and is described as giving compensating action.

It's interesting that like the Kodak 1927 dev I linked to they are used more dilute.

Ian
 
Arm and Hammer Washing Soda = sodium carbonate
 
I had thought my question quite simple: a liter of water in which 100 mg of sodium sulfite is dissolved has a pH of X. A liter of water in which 50 mg of water is dissolved is less alkaline. Some sodium carbonate could be added to the second solution to bring its pH to X. How much sodium carbonate would that be???
 
An old textbook tells me D23 has a ph of 7.80. It also says that metol needs a ph of between 6.0 and 7.0 to function. Since D23 diluted 1:3 still functions as a film developer, it seems pretty obvious that adding sodium carbonate to a 5% solution is probably moot, dontcha think?
 
It isn't so simple as just the pH, halving the Sulphite drops the pH by far less than I think you're assuming, if it was 8.5 then it'll drop to around 8.2 and you'd need to add very little Sodium Carbonate to restore it.

But Sodium Sulphite is a preservative and weak silver solvent which gives some physical development at 10% - 100gms/litre so when you cut it's level and add Carbonate you'll have a faster working developer which won't be as fine grained.

Anscojohn mentioned the Agfa 14 fine grain developer which uses 1 g/litre Carbonate, Agfa 12 uses a higher level of Sulphite 125 g but needs 6 g/litre Carbonate to compensate as well as a higher level of KBr

Agfa 12

Metol 8 g
Sodium Sulphite (anhyd) 125 g
Sodium Carbonate 6 g
Potassium Bromide 2.5 g
Water to 1 litre

So you probably don't need to add any Carbonate, D25 gives finer grain than D23 because the Metabisulphite reduces the pH.

Ian
 
OTOH you might want to look at W Beutler's High Definition developer which is used quite dilute so needs a higher pH:

Metol 5 g
Sodium Sulphite (anhyd) 25 g
Sodium Carbonate (anhyd) 25 g
Water to 1 litre

Use 1:10

It would be relatively easy to come up with a developer somewhere between D23 & Beutler.

Ian
 
Likely Not So

lensmagic said:
I had thought my question quite simple: a liter of water in which
100 mg of sodium sulfite is dissolved has a pH of X. A liter of water
in which 50 mg of water is dissolved is less alkaline.
Click to expand...

As I've mentioned in my post 2 this thread and Ian has pointed
out the ph will Very likely be Very nearly the same. I've not
checked sodium sulfite's ph vs concentration curve but it
is possible that the ph is actually higher at the lower
concentration. It is not uncommon for ph curves to
top out while within single digit percentages.

To satisfy yourself you might search Google for sodium
sulfite's 'vs' curve. Dan
 
I was under the misapprehension that the quantity of sodium carbonate to be substituted is something that could be calculated. Based on what I am reading here, I now think the sodium carbonate substitution would have to be worked out by trial and error using a device that measures pH.
 
You can't substitute one for the other because they have different effects in a developer, Carbonate is purely an Alkali/Accelerator while Sulphite is a Preservative and only a mild alkali. The amount of Carbonate needed to raise the pH difference between 100 and 50 g of Sulphite will be quite small maybe around 1 g.

Just cutting the Sulphite by 50% will increase the Metol's activity anyway, regardless of the minor drop in pH.

Ian
 
Just cutting the Sulphite by 50% will increase the Metol's activity anyway, regardless of the minor drop in pH.

Ian[/QUOTE]
*************
This seems counterintuitive.
 
Just cutting the Sulphite by 50% will increase the Metol's activity anyway, regardless of the minor drop in pH.

Ian[/QUOTE]

Why would REDUCING the sodium sulfite concentration INCREASE Metol's activity?
 
Once the Sulphite is over a certain level then it has a high solvent effect which restrains the developer, so when you dilute a developer like ID-11/D76 to 1+1 or 1+3 you actually get increased activity, relative to the effects of the dilution itself, and better film speed because the Sulphite level has dropped below the threshold.

Dropping the Sulphite from 100gm/litre to 80gm/litre is used in ID-68/Microphen to help increase the effective film speed compared to ID-11, and Ilford's PQ version of ID-11/D76 (Autophen - discontinued).

Ian
 
Once the Sulphite is over a certain level then it has a high solvent effect which restrains the developer, . . . .
Ian[/QUOTE]

Is it known when the "certain level" is reached? For example, at so and so many grams Sodium Sulphite per liter the solvent effect kicks in. It seems we are trying to strike a balance here--enough sulphite to curb oxidation, but not so much as to create excess solvency and restrain the action of the developing agent.
 
No Specific Level

lensmagic said:
Once the Sulphite is over a certain level then it has
a high solvent effect which restrains the developer, .Ian
Click to expand...

Is it known when the "certain level" is reached? For example, at
so and so many grams Sodium Sulphite per liter the solvent effect
kicks in. It seems we are trying to strike a balance here--enough
sulphite to curb oxidation, but not so much as to create excess
solvency and restrain the action of the developing agent.[/QUOTE]

..........................................................................................

Sulfite's solvency of image silver does not kick in at some
specific level. I'd think its effect tapers off at very high
levels. Crawly found sulfite's solvency effect to still
be declining at levels of two grams per liter.

Very low levels of sulfite may be used if the
developer is used one-shot. Dan
 
If you are expecting two solutions with the same pH to have the same developing rate, you will be very disappointed. A solution of Amidol at pH = 7.0 is quite active while pure distilled water, which has pH = 7.0, has 0 developing rate. If you want to find the photographic effect of a given change of pH, you must do a photographic experiment, not a physical chemistry one.
 
If you would like to try a developer with no sulfite (not even any sulphite), you could try the following:

1 tsp sodium carbonate (anh).
1/2 tsp ascorbic acid crystals.
1/16 tsp Metol
Water to make a quart. A liter is close enough.

Treat it as full strength D-76.

If you abhor the teaspoon measures, you could weigh them the first time so you can duplicate the results with utmost precision if you so desire. You could also measure the pH so as to test whether any alkali other than Na2CO3 that gives the same pH will give the same photographic result.
 
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