Kodalk substitute

[Igor Savchenko]

During the war, Agfa used a Kodalk substitute. I would have to go back over a lot of notes to find this, but if you need it, I might be able to find it. A simple solution exists. I know that, but it is hidden in reams of notes. sorry.

PE

I'm very interested, too, if you could find your notes on that, please. Once we already touched this issue, but never came to exact formulas. Maybe the following quote will help you:

(there was a url link here which no longer exists)

"Quote Originally Posted by Photo Engineer View Post
In den Begiebezustatze ist Borax-Ersatz je nach Saure bestimmung oder Borax mit Natrium Carbonate.

During the war, Agfa could not get Borax from the US easily so they made a substitute. This quote above is directly from what I copied from an Agfa formula many years ago. It was published (AFAIK) in the FIAT reports.

I hope I got that right.

PE
My quote is incorrect above due to my poor rememberance of German. The exact information was on two pages and I had to combine the two.

Basically, they used Ersatz Borax or acid to adjust pH in solutions and the ersatz Borax was made from Sodium Carbonate and Bicarbonate or with Sodium Bicarbonate and Sodium Hydroxide. The acid used depended on the solution being adjusted.

I looked up my notes again today to see if I could clarify this and use English which is a bit better than my German.

PE "

 

[Rudeofus]

Igor: borax allows you to go acidic or caustic, see my table above. And as it just so happens, in caustic direction direction you cover about the same pH range as with carbonate/bicarbonate. For pH levels below 9, though, you will be out of luck, this borax ersatz will not help Relayer.

 

[Photo Engineer]

Igor;

After reading my posts, I remembered enough to say that Agfa used a mix of Carbonate + either bicarbonate or hydroxide, and they finalized the pH adjustment with an appropriate acid. So, knowing the pH was critical here as that was the aim point. The rest was merely the addition of carbonate to get close and then tweaking the pH. Once they had the pH right, they could then record how much of each ingredient they added and make that the starting point for the next run.

This was not an exact science back then. In fact, their starting materials varied quite a bit and their description was quite vague. so is my memory, but this description and my two posts above that you refer to summarize things well.

PE

 

[Relayer]

just make some experiment: in 1l of water at 32C dissolve 1.92g of Sodium carbonate. then add 6.92g of borax - its dissolved very quickly! solution is muddy, but clear after 2-3min. check pH - 9.2 at 24C. now put this solution in open bottle and will be recheck pH later

recheck pH after 24 hour - still 9.1-9.2. any comments?

 

[Gerald C Koch]

... he wants a buffer at pH 8.2 for a photographic developer.

NO, he wants a substitute for sodium metaborate in DK-50 and DK-76 neither of which has a pH this low. It's interesting how threads veer off from the original post.

 

[Relayer]

NO, he wants a substitute for sodium metaborate in DK-50 and DK-76 neither of which has a pH this low. It's interesting how threads veer off from the original post.

)) not only in DK50. my question in general related to alternative buffer formulas with pH in "kodalk" range. by example well known carbonate-bicarbonate buffer found in E-6 FD. carbonate-borax also working as buffer solution, but poor described.
PS last time I working on PC developer with very low pH=7.2. For such pH I found that Na2HPO4–NaH2PO4 buffer solutions is good because have range 6.0-8.0

 

[Rudeofus]

NO, he wants a substitute for sodium metaborate in DK-50 and DK-76 neither of which has a pH this low.

According to Kodak Patent US3998637 the developer DK-50 has a pH of 9.5. This pH can be achieved both with a carbonate/borax buffer and with a carbonate/bicarbonate buffer.

According to Patent US2165797 the DK-76 developer has a pH of 8.5, which is nicely in borax/carbonate territory.

No need for NaOH in either dev ....

 

[Gerald C Koch]

Thanks Rudeofus this is the information that we need! We have been like the philosopher's from the story arguing about how many teeth a horse has.

 

[Relayer]

Carbonate-bicarbonate buffer, g/l
Na2CO3 NaHCO3 pH
1,060 7,560 9,16
2,120 6,720 9,4
3,180 5,880 9,51
4,240 5,040 9,78
5,300 4,200 9,9
6,359 3,360 10,14
7,419 2,520 10,28
8,479 1,680 10,53
9,539 0,840 10,83

 

[Photo Engineer]

The ratio is important but so is the buffer capacity. So, to get pH 9.5 you could use 3.18/5.88 and then find that the buffer capacity was too low. You also need the moles/liter of Kodalk in order to estimate the buffer capacity and then you can guesstimate a starting figure for the substitute of carbonate/bicarbonate.

PE

 

[Rudeofus]

by example well known carbonate-bicarbonate buffer found in E-6 FD. carbonate-borax also working as buffer solution, but poor described.
PS last time I working on PC developer with very low pH=7.2. For such pH I found that Na2HPO4–NaH2PO4 buffer solutions is good because have range 6.0-8.0

The reason you read little about borax-carbonate buffer is because it is technically two buffers in one: carbonate-bicarbonate and metaborate-borax. Chemists seem to like buffers with as few compounds as possible to avoid interaction with the substances they want to provide a stable pH with. There are plenty of resources for these two individual buffers on the web, e.g. here.

 

[Alan Johnson]

Because the other ingredients of DK-50 will affect the pH, targetting the pH of the final developer using a table won't work.
To be sure it seems to be needed to make measurements of the final mix with a pH meter.

 

[RalphLambrecht]

i thought, borax is kodalk.

 

[Ian Grant]

i thought, borax is kodalk.

No, Sodium Metaborate was sold as Kodalk by Eastman Kodak, but it's made from Borax and Hydroxide.

Ian

 

[Gerald C Koch]

Borax (sodium orthoborate) is a very mild alkali but Kodalk (sodium metaborate) is a strong one with a pH near that of sodium carbonate. Kodak used Kodalk in several of its developers instead of sodium carbonate since it will not release carbon dioxide when the film is placed in the stop bath.

 

[Photo Engineer]

Kodalk is listed as the Sodium salt of Boric acid and also as Sodium Metaborate Octahydrate CAS#.035585-58-1. So, it can be made on a molar basis by taking plain boric acid and adding Sodium Hydroxide to it until you reach the pH that you wish.

That will do the trick.

PE

 

[Ian Grant]

It's best to use Kodak's own recommendation of Borax and Hydroxide which they've published many times over the years in various Professional Handbooks.

They clearly show that 10g Sodium Mertaborate (Kodalk) can be replaced by 7g Borax and 1.5g Sodium Hydroxide, and for DK20, DK50. DK60, DK93 etc.

Ian

 

[Relayer]

found some interesting:
* borax with sodium carbonate react only at high temperature (~800-900C)
* boric acid react with carbonate and produce borax:
4H3BO3 + Na2CO3 + 4H2O = Na2B4O7+10H2O + CO2
* reaction between calcium metaborate and sodium carbonate produce sodium metaborate
Ca(BO2)2 + Na2CO3 = 2NaBO2 + CaCO3

 

[BradS]

You're NOT a chemistry person? Fooled me.

Jon

no...I'm definitely not a chemistry person. My sum total of formal education in chemistry amounts to one year of High school chemistry, one year of general chemistry in college and some independent study of a couple of text books in Organic Chemistry.

I am a math person....ten years of grad school in Math & Statistics and a few more during undergrad.