Progress on XTOL-concentrate

[albada]

Congratulations, Mark! Next time you visit Ireland, let me know and I'd love to buy you a drink—thank you for your impressive work.

Thanks for the encouragement! It's nice to know that others value this effort.

Sodium ascorbate was from ebay, it is a food supplement.

I just did a search on both ebay and amazon, and sodium ascorbate is plentiful. Where have I been hiding? Photographer's Formulary doesn't carry it, and apug postings from 5-8 years ago made it sound like it was hard to find (it's used in Mytol), so I assumed it's hard to find. Not so.

Conclusion- some of the phenidone survived 34 days oxidation and was regenerated.
It seems likely all the ascorbate is oxidized first, before the phenidone.

Alan, these are valuable results. It means we could do the following:

1. Mix Mytol or something similar.
2. Store it recklessly, letting it sit a long time in a partly filled bottle. It'll go off.
3. Each time it's used, drop 1/8 or 1/4 or 1/2-teaspoon of sodium ascorbate into the beaker. Then the dev will work fine.

This idea relies on the original ascorbate in the developer acting as a preservative, preserving the sulfite and Phenidone/Dimezone. Normally, we would want the sulfite to preserve the ascorbate, but that's not what happens. Instead, the ascorbate preserves the sulfite, which was (until now) considered a problem. We are taking advantage of that fact by adding ascorbate just before use, knowing that the other chemicals will be fine. We have turned a problem into an advantage.

This idea also relies on the observation that having excess ascorbate in a dev is harmless. This is what Gainer found, and my tests confirm it. But we'd need to run more tests before relying on this. If true, it means that the ascorbate added at time-of-use does not need to be measured accurately; hence the use of teaspoons.

These findings also suggest that one could revive dead XTOL by adding ascorbate to it. More experiments to try...

Mark Overton

 

[albada]

I published the article about Mocon (aka 214D). Here it is:

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

 

[Rudeofus]

Attachments show that the solution containing sodium ascorbate alone went orange, strongly suggesting the orange color is due to the formation of an ascorbate oxidation product, it does not come from phenidone.

Phenidone turns orange quickly at pH>7. Your test with Phenidone alone may not be conclusive.

 

[Alan Johnson]

I do think the colors shown in the attachments I posted are relevant to the chemical changes and color changes likely to occur in the concentrate,mainly because the pH of the concentrate (with a little water) ,the sodium ascorbate solution and the phenidone solution are all very similar, just over pH=5.
The phenidone doesn't see higher pH in the concentrate.

 

[MattKing]

At the risk of making all of the excellent efforts of all of the contributors to this thread superfluous, wouldn't it be even better to have developed some kind of an easy to use test for the activity of stored, working strength X-Tol?

Something like the retained silver tests or something as easy to use as litmus paper.

 

[Photo Engineer]

Matt, there was a thread on this a while back. There is a good test that relies on the time of development o achieve a given density of fresh and kept developer. Small clips of film are used.

PE

 

[MattKing]

Matt, there was a thread on this a while back. There is a good test that relies on the time of development o achieve a given density of fresh and kept developer. Small clips of film are used.

PE

PE:

That is a "good" test, but not necessarily an "easy" test.

The need for the test is most pronounced for those of us who have inconsistent film use needs, and temporary darkrooms - so something that just requires us to put a couple of drops of a solution into a few millilitres of developer and check for precipitate would be wonderful.

 

[Photo Engineer]

Matt;

That is the problem.... There is no "easy" test.

PE

 

[MattKing]

Matt;

That is the problem.... There is no "easy" test.

PE

PE:

Are aware whether any research work has been done with a goal of developing such tests? Not just for X-Tol, but for other chemicals as well (e.g. E6 and C41). It seems to me that in the current circumstances, such tests would be much more likely to be commercially valuable than when volumes were higher.

 

[PhotoJim]

PE:

Are aware whether any research work has been done with a goal of developing such tests? Not just for X-Tol, but for other chemicals as well (e.g. E6 and C41). It seems to me that in the current circumstances, such tests would be much more likely to be commercially valuable than when volumes were higher.

High-volume users have good data already on total development capacity. They don't need to test the chemistry; they can simply replenish or discard based on the amount of film processed in the chemical.

If you need a developer that will work well after years of storage, XTOL is not your developer, unfortunately.

 

[MattKing]

If you need a developer that will work well after years of storage, XTOL is not your developer, unfortunately.

I know, that is why I currently use replenished HC-110 .

But I would like to try replenished X-Tol

 

[Photo Engineer]

We used chemical analysis! And control strops! Thats about it. No simple test.

PE

 

[Rudeofus]

Are aware whether any research work has been done with a goal of developing such tests? Not just for X-Tol, but for other chemicals as well (e.g. E6 and C41). It seems to me that in the current circumstances, such tests would be much more likely to be commercially valuable than when volumes were higher.

There is such a test and it's called "running a test strip". The biggest problem with this test and Xtol is that (at least according to some accounts) Xtol went from fully working to complety inactive in the brief timeframe between clip test and dev run.

Mark's suggestion "just add some pH balanced AA to the mix right before using it" seems like the easiest method for overcoming this issue. It should work both with his dev and with Xtol.

 

[Alan Johnson]

Mark's suggestion "just add some pH balanced AA to the mix right before using it" seems like the easiest method for overcoming this issue. It should work both with his dev and with Xtol.

One can calculate how much sodium ascorbate to add assuming all the oxygen in the air space is used up.
2C6H7O6Na.......................+ O2..........->2C6H5O6Na +2H20
Sodium ascorbate............ Oxygen.......... Sodium dehydroascorbate
2x198.1=396.2g................22.4L=107L air
When the container is opened, add 3.7g sodium ascorbate for each liter of air space above the developer.

 

[Rudeofus]

One can calculate how much sodium ascorbate to add assuming all the oxygen in the air space is used up.

You'd also have to account for all the Oxygen diffusing into the container ...

 

[albada]

You'd also have to account for all the Oxygen diffusing into the container ...

You'd also need to account for loss from the Fenton reaction, which is hard to predict. When adding ascorbate upon use, it may be best to assume that all the ascorbate has been destroyed.

Mark Overton

 

[Rudeofus]

You'd also need to account for loss from the Fenton reaction, which is hard to predict. When adding ascorbate upon use, it may be best to assume that all the ascorbate has been destroyed.

IIRC, the Fenton reaction only catalyzes (read: speeds up) the destruction of Ascorbic Acid, but it is still aerial Oxygen (or whatever other oxidizer is around) which does the oxidizing.

 

[albada]

Some good news about longevity testing of the concentrate:
It's been six months in the refrigerator, half full and opened once a month, and still no evidence of yellowing.

I have some D316 and Mocon in the refrigerator and freezer. The bottles of D316 are half full, and I've been opening them once a month for a few minutes to simulate typical hobbyist usage. It's been six months, and there's still no evidence of yellowing (oxidation) visible in a glass eyedropper. For comparison, when stored at room temperature and *not* opened, these glycol-based ascorbate concentrates start yellowing after 2-3 months. Evidently, they like to be kept cold.

Mark Overton

 

[sun of sand]

I'm not sure where frame 24 is. Could you give the posting number? It's in the upper-right corner of the posting. For example, this is posting #521.

BTW, having XTOL last 4 years is amazing. You mention keeping it chilled: Do you have issues with precipitate collecting at the bottom of the bottle? When I tried refrigerating my XTOL, I quickly got some precipitation.

Mark Overton

I used some of my 5L xtol recently at 1:1 to develop 3 films
assorted
plus-x
tri-x
arista something
shot as much as 3 years ago ..maybe longer

developed for 9 minutes to compensate for the age of film
the label on the bigger untouched bottle was actually Nov 9 2007 ...not 2009
this was on a large maybe 1/2 gallon brown glass Bud bottle with plastic press fit cap

bottle I used was a 40oz bottle half full. I would reuse the developer stock and that bottle had been opened/used since I mixed it ..maybe late 2008 at latest

My basement stays 43-45 in winter and never above 65 in summer
the concrete floor must be colder
precipitate? I don't know if there is any sedimentation at the bottom
there are some "floaters" in the 1/2 used xtol. I didn't even filter it as it was unimportant film
My dektol will settle out upon standing which then needs a shake
Don't believe I've noticed this with xtol but i don't shake it and probably haven't held the bottle up to light

I'll pour it out and take some photos one day


still
late 2007 half used/reused bottle still develops film 1:1 in 9 minutes
going on 7 years

whether it's 100% or 91.4% i can't tell you
It is a clearish yellow in color
I remember the fresh mixed xtol being an off white color
milky perhaps

but I haven't mixed any since then. I don't use xtol anymore