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Photo Engineer
12-27-2011, 07:45 PM
Go here: http://en.wikipedia.org/wiki/Ascorbic_acid and here: http://en.wikipedia.org/wiki/Sodium_ascorbate to see the structures of AA and Sodium Ascorbate. Your equation is not correct, as you cannot get free Boron and free Oxygen from this reaction.

Sodium Metaborate + AA = Sodium Ascorbate and Boric Acid which lowers the pH. By lowering the pH, if there is enough Borate or Metaborate and if the pH is high enough, the equillibrium shifts and the buffering ability of the ingredients kick in to maintain the pH as much as possible. That is a simple explanation of what is going on.

And, BTW, Borates are banned in many US Citrus states as Borates are toxic to Citrus trees.

PE

albada
12-28-2011, 02:07 PM
Sodium Metaborate + AA = Sodium Ascorbate and Boric Acid


I analyzed the above equation, and got this:


3C6H8O6(AA) + 3NaBO2(metaborate) => 3C6H7NaO6(ascorbate) + H3BO3(boric acid) + B2O3


Notice the extra 2 B's and 3 O's, which I combined into boron trioxide, which I doubt we'll actually get. Am I closer this time?

Do you know if this reaction would occur when mixed in the PG? Or does it only occur in water? I'm wondering if we actually get ascorbate in the PG.

Thanks as always,

Mark Overton

Photo Engineer
12-28-2011, 02:13 PM
Mark;

This is a very complex reaction due to the presence of Borate which can make a variety of resultant anions. Don't worry about it. It is difficult for met to solve. I like easier equations. You are coloser, but the mixture will contain Ascorbates, Borates, Metaborates and the PG even makes some salts and esters with the materials present. You see, the Boric Acid will react with some of the metaborate and also with the OH ion present (being alkaline).

Just measure the pH and be reassured that if you adjust it to where you want it to be, things should work out.

Don't forget the toxicity of Boron containing salts to Citrus plants. IDK where you are located, but some of these salts are restricted in CA and FL.

PE

albada
12-28-2011, 11:42 PM
Just measure the pH and be reassured that if you adjust it to where you want it to be, things should work out.


Ron, Then that's what I'll do. I picked up the pH meter today.

The formula I posted recently has a pH of 8.05. The test-strips said 7.8-7.9. You were right: They're significantly off.



Don't forget the toxicity of Boron containing salts to Citrus plants. IDK where you are located, but some of these salts are restricted in CA and FL.


With that encouragement, I decided to try removing the borate. The sulfite becomes the sole alkali, and I added ascorbic acid until the pH dropped to 8.0. Without the PG, here's the resulting simple 1-liter formula:


Sodium sulfite ................ 90 g
Phenidone ..................... 0.15 g
Ascorbic acid ................. 3.5 g
Target pH = 8.0. 7.5 min for TMY at 20C.


That's it! And with a brief exam, I can't tell the difference between this formula and XTOL. I'm surprised. Has anyone before tried this simple PC-plus-sulfite formula?

Mark Overton

analog what is that?
12-29-2011, 12:32 AM
Re the test strips and the pH-meter :
Test strips 7.85 +- 0.20
pH meter 8.05 +- 0.15

Your test strips was definitely NOT significantly off, there is not anything in the whole world that is an EXACT measure, especially when it comes to pH measurements, electrode, exact mix, temperature.... a lot of stuff enters the equation here.

I'd say your reasoning from the start based on the test strips was sound, and that you was in the ball park all the time.

Photo Engineer
12-29-2011, 09:54 AM
Mark;

The pH meter has some compensation for temperature and high salt content and therefore is more accurate than the strips which do not (obviously) have any means of compensation. The results of this measurement are as I suspected and the results are excellent. Congratulations.

I'll bet the results make you very happy too! That is how I feel when something works out well. :D Enjoy.

PE

Alan Johnson
12-29-2011, 11:57 AM
Ron, Then that's what I'll do. I picked up the pH meter today.

The formula I posted recently has a pH of 8.05. The test-strips said 7.8-7.9. You were right: They're significantly off.



With that encouragement, I decided to try removing the borate. The sulfite becomes the sole alkali, and I added ascorbic acid until the pH dropped to 8.0. Without the PG, here's the resulting simple 1-liter formula:


Sodium sulfite ................ 90 g
Phenidone ..................... 0.15 g
Ascorbic acid ................. 3.5 g
Target pH = 8.0. 7.5 min for TMY


That's it! And with a brief exam, I can't tell the difference between this formula and XTOL. I'm surprised. Has anyone before tried this simple PC-plus-sulfite formula?

Mark Overton

The formula type is new to APUG as far as I know.
But it is unbuffered, see posts #25 and #26 in this thread.
It may oxidize to the more acidic(I think) dehydroascorbate and fall in pH.
But one would have to do a long term comparative test with Xtol, both in contact with air,to see.

analog what is that?
12-29-2011, 12:55 PM
Mark;

The pH meter has some compensation for temperature and high salt content and therefore is more accurate than the strips which do not (obviously) have any means of compensation. The results of this measurement are as I suspected and the results are excellent. Congratulations.

I'll bet the results make you very happy too! That is how I feel when something works out well. :D Enjoy.

PE

How can you say that? Both measurements fall in roughly the same range; a couple of tenth's off which is insignificant is this context....

He could have done just as well with a 15$ chinese pH meter, and changed it every year, ikf one was afraid that the *unusual environment* would eventually do in the cheap meter.....

I don't think much was achieved here but demonstrating a tour-de-force that means nothing for the rest of us readers of this thread, this is supposed to be of value to rank amateurs and one need to have feet planted solidly on the ground.

Sorry, but I have spent years around appartus like this in my work life, running everyday tests IRL...............

Hexavalent
12-29-2011, 01:35 PM
How can you say that? Both measurements fall in roughly the same range; a couple of tenth's off which is insignificant is this context....

He could have done just as well with a 15$ chinese pH meter, and changed it every year, ikf one was afraid that the *unusual environment* would eventually do in the cheap meter.....

I don't think much was achieved here but demonstrating a tour-de-force that means nothing for the rest of us readers of this thread, this is supposed to be of value to rank amateurs and one need to have feet planted solidly on the ground.

Sorry, but I have spent years around appartus like this in my work life, running everyday tests IRL...............

With the exception of $ task-specific items, pH "test-strips" are a poor choice for any truly meaningful quantitative work. The investment in a quality meter will pay for itself by providing trustworthy accurate readings.

analog what is that?
12-29-2011, 01:45 PM
Well that is true, but NOT in this case, just look at the numbers............................

If you think an expensive pH meter is a necissity or a requirement for doing this, you are doing your readers a disservice, given the state of "analog" photography, we most assuredly needs every experimenter and anyone willing to use film, to keep this thing alive.

Hexavalent
12-29-2011, 01:48 PM
If you think an expensive pH meter is a necissity or a requirement for doing this..

I don't think anybody said that. What was said is that pH "test strips" can be misleading.

Photo Engineer
12-29-2011, 01:54 PM
I would like to add that in a dilute working solution the pH meter and test strips will be closer together, but in a concentrate they can deviate substantially due to the high salt content and its effects on pH as measured by strips.

Also, since pH is temperature dependent and we don't know the temperature here, we can be sure that it is at least measured by the Hanna meter. There is also some compensation internally for temperature variations.

PE

analog what is that?
12-29-2011, 04:11 PM
Well we now agree that the test strips and the pH meter was close in this case, so close it really didn't matter.

We agree on temperature influernce (I already said that at the beginning), the practical solution - and that is what counts on a kitchen table budget, which is what matters here for the REST of us - it is really very simple, just let all fluids adjust themselves to the same kitchen temperature, and the difference is moot.

I still hold it is a more pratical solution for the rst of us to order a 15$ pH meter from Hongkong and replace it as necessary.

What was the price of that thing, did you say?

And we should all focus on the fact that pH was double-checked here aqnd hovers around pH 8, I doubt that anyone can guarantee the value down to the last 1/10, since we wasn't there, have no idea if the meter was properly set up etc etc etc, this is not like buying a yardstick......

analog what is that?
12-29-2011, 04:15 PM
Re the test strips and the pH-meter :
Test strips 7.85 +- 0.20
pH meter 8.05 +- 0.15

Your test strips was definitely NOT significantly off, there is not anything in the whole world that is an EXACT measure, especially when it comes to pH measurements, electrode, exact mix, temperature.... a lot of stuff enters the equation here.

I'd say your reasoning from the start based on the test strips was sound, and that you was in the ball park all the time.

Yes there it was my reference to temperature to begin with.............

analog what is that?
12-29-2011, 04:22 PM
Checked out the Hanna meter, it is virtually the same as my Hongkong meter, included the buffers to set up and control the meter, save for one thing that I have no use for: temperature meter. Not necessary since I always store all chemistry including the fresh water needed in a termostat controlled room at 20,4 centigrade for at least 24 hrs....

This cost 90 bux from Amazon plus shipping, mine guaranteed to the same 0,1 units did cost 15 bux from Hongkong, including postage.............

Do your own math.

albada
12-29-2011, 05:02 PM
The formula type is new to APUG as far as I know.


I went ahead and posted a slightly improved formula (with a higher pH) as a new thread. The name "PC-Sulfite" follows the way Gainer named his developers, and is certainly descriptive of the formula.

Mark Overton

albada
12-29-2011, 05:52 PM
I'll bet the results make you very happy too! That is how I feel when something works out well. :D Enjoy.


Yes, I am enjoying this! And certainly appreciating your assistance!

As you can tell from my intro in the new PC-Sulfite thread, I can hardly believe that something so simple is actually new. That developer certainly is down to the bare essentials, and yet it looks as good as XTOL. Hard to believe, and yet I've got the neg's to prove it.

Mark Overton

Photo Engineer
12-29-2011, 06:10 PM
Well, the next thing is to work on a concentrate. Here is another hint: Kodak was working (at the end) on small packets of powdered developers, extreme concentrates, and (ta da) tablet developers similar to Alka-Seltszer. Drop into water for a single use. Makes 1 L.

What do you think of this? They were working on a whole host of new concepts in delivery to the customer, but a failing market killed all of it off.

PE

Ryuji
12-29-2011, 06:27 PM
If you think an expensive pH meter is a necissity or a requirement for doing this, you are doing your readers a disservice, given the state of "analog" photography, we most assuredly needs every experimenter and anyone willing to use film, to keep this thing alive.

Well, let's examine the disservice. The disservice is that, long threads are continued to modify one thing into another, based on incomplete understanding on the nature of the technology and poor judgment. To put it into your perspective, “given the state of analog photography” what we most assuredly need are a good practical and sustainable processing system, not every amateur experimenter or bastardizer, and anyone willing to use film to actually create art or commercial art that is worthy of some audience.

pH meter is certainly not a requirement for photographers. But if you are a chemist formulating formula and being responsible about what he or she reports, it is crucial. At the same time, measuring pH is not a trivial business. It is a lot harder than measuring voltage or complex impedance, for that matter. All pH electrodes have limitations, and photographic chemicals are one of the most tricky solutions to measure, and also just be compatible with the electrode... many people buy wrong electrode and they have no idea of the limitations of the measurements they are making. A pH meter don’t measure pH, unless you calibrate it correctly, maintain it correctly and use it correctly. Standard pH calibration buffers are to be used at 25C. But the photographic solutions are typically used at 20C. Solution pH depends on temperature and dilution, but each solution responds to these factors differently. The temperature compensation functions built into some meters only take care of the temperature dependency of the electrode, not the standard buffer solution or the test solution. (Therefore, many scientists simply do not use such function; they avoid the issue by carefully designing the experimental protocol. Industrial engineers simply incorporate these factors into the plant control programs.)

Incidentally, 0.2 unit variation is pretty lousy for a film developer. It’s okay for print developers. If fix or wash aid, an error of 0.2 unit is insignificant.

Also incidentally, it is true that test strips are lousy. They have good uses, in many cases adequate, but for careful experimentation of anything, it is not. Also, careful experimentation is always expensive. It is certainly not for people who puts budget before knowledge.

Ryuji
12-29-2011, 06:55 PM
With the exception of $ task-specific items, pH "test-strips" are a poor choice for any truly meaningful quantitative work. The investment in a quality meter will pay for itself by providing trustworthy accurate readings.

And anyone who is not willing to make every effort to be accurate should not call their work science or engineering.