Stand Developer Concentrations

[Kirk Keyes]

My idea of an expert is one who knows more and more about less and less until he knows all there is to know about nothing.

I know this is a very popular notion these days, but that is a description of someone that is pretty useless. I guess you and I have met an entirely different set of experts.

 

[Tom Hoskinson]

Side note to the discussion for those that are not familiar with the actual process that is konwn as the scientific method - there is much more to it than "trial and error". In fact that really doesn't fit in to the scientific method. A better discription of the scientific method is as follows, there are 4 steps:

1. Observation and description of a phenomenon or group of phenomena.

2. Formulation of an hypothesis to explain the phenomena. In chemistry, the hypothesis often takes the form of a causal mechanism or a mathematical relation.

3. Use of the hypothesis to predict the existence of the phenomena, or to predict quantitatively the results of new observations.

4. Performance of experimental tests of the predictions by several independent experimenters and properly performed experiments.

(The above was mostly taken from the excellent web page http://teacher.nsrl.rochester.edu/phy_labs/AppendixE/AppendixE.html )

I completed Step 1 sometime before I started this thread. I originally mentioned pH, but then PE pointed out that buffer action combined with the solution pH was really probably a better hypothesis. So now we are up to step 3. As I have no experience with stand development, I suggest that anyone who wishes can try to make some observations (Step 3) and see if the hypothesis holds up. Then we can move to Step 4.

"Trial and error" kind of trivializes the entire process, as well as puts an imprecise spin on the actual process.

I apologize to those that find these sorts of posts uninteresting.

I've found this thread interesting - and that it has exhibited a tendency to wander off the original subject from time to time.

Regarding step 3: "Use of the hypothesis to predict the existence of the phenomena, or to predict quantitatively the results of new observations. "

This step contains an implicit requirement for the ability to record quantitative data. One data type of interest that has been discussed is microdensitometry data. Has anyone identified an instrument which has the right spectral response coupled with the requisite spatial resolution.

My old Perkin-Elmer microdensitometer won't do the job.

Any recommendations?

 

[Kirk Keyes]

Basically, the hypothesis is that an ascorbate developer with minimum alkali will make a good stand developer whether or not the concentration of developing agents is such as to cause local starvation because the products of ascorbate developers are more acidic than those of the hydroxy phenols. To test the hypothesis, I used an ascorbate-amidol developer in a glycol stock solution in order to make it easy to change athe amount of alkali separately.

Patrick - Interesting idea. I'm not sure you've really "proven" your idea "because the products of ascorbate developers are more acidic than those of the hydroxy phenols" with out more work, i.e. testing with hyrdoxyphenol-based developers to make comparisions, and of course actual micro-pH measurements, which I know are a more complex level of instrumentation that most of us have.

Thanks for sharing the idea and results with us!

The minimum amount of TEA was found by titrating with a pH indicator from a swimming pool test kit to get the first tint of pink.

I do have one question - I may be missing a point here, but why does titrating as you mention give a minimum amount of TEA? (I assume you mean that you titrated some water with TEA to the phenolphthalein endpiont?) That means that your endpoint should be somewhere around pH 8.3, depending on where you get your value of the endpoint of phenolphthalein.

I'd be interested in seeing the graph if you would post it.

And did you happen to make any observations on edge effects, as that, and not compensation, was really my initial thougth with this thread.

Kirk

 

[Kirk Keyes]

This step contains an implicit requirement for the ability to record quantitative data. One data type of interest that has been discussed is microdensitometry data. Has anyone identified an instrument which has the right spectral response coupled with the requisite spatial resolution.

My old Perkin-Elmer microdensitometer won't do the job.

Any recommendations?

Tom - I'm glad you've enjoyed the thread - me too! And I'm actually excited that one person has already read the info on the scientific method and asked a good question from it! Thanks!

I know you are not trying to hijack this thread, but if you would like to start a thread on the subject of techniques that could be used to make microdensity measurements, I would be happy to join in on it with you.

Kirk

 

[Tom Hoskinson]

Good suggestion, Kirk. I'll start another thread on microdensitometry techniques/questions.

As you may know, Pyrocat-HD is my primary film developer and I use it with either minimal agitation or semi-stand agitation. I can see positive differences in my LF contact prints and would like a better understanding of what is going on.

The approach to understanding that I favor is a Statistical DOE (Design Of Experiments). In order to accomplish this I need to make repeatable, quantifiable (and applicable) measurements.

 

[gainer]

Patrick - Interesting idea. I'm not sure you've really "proven" your idea "because the products of ascorbate developers are more acidic than those of the hydroxy phenols" with out more work, i.e. testing with hyrdoxyphenol-based developers to make comparisions, and of course actual micro-pH measurements, which I know are a more complex level of instrumentation that most of us have.

Thanks for sharing the idea and results with us!



I do have one question - I may be missing a point here, but why does titrating as you mention give a minimum amount of TEA? (I assume you mean that you titrated some water with TEA to the phenolphthalein endpiont?) That means that your endpoint should be somewhere around pH 8.3, depending on where you get your value of the endpoint of phenolphthalein.

I'd be interested in seeing the graph if you would post it.

And did you happen to make any observations on edge effects, as that, and not compensation, was really my initial thougth with this thread.

Kirk

No, as I said above, I cannot prove my hypothesis. I can only use it as a working hypothesis until someone does a test that disproves it.

There's a little more to it than the titration. You are right about 8.3. I am using amidol as the Quasi-catalyst where I would ordinarilly use phenidone. I wanted to neutralize the stock solution's ascorbic acid without getting too much above the point where there is some activity. The less alkali there is in the working solution the more likely it is to be affected, one way or the other, by local development products. 3 ml of TEA per liter is not much. It's off the bottom end of the chart that Dow shows for 99% TEA, which is what I have, and that bottom value is about 8.

The concentration of amidol I use is 1/100 that of the ascorbic acid. I don't know exactly how to calculate the amount of TEA required to neutralize a gram of ascorbic or erythorbic acid. Perhaps our resident chemistry expert can say. I do know that with the concentrations of agents that I tested at first, the usual rough test of soaking a piece of exposed film in it for 2 minutes gave practically no change in density. 40 minutes at 75 degrees was about normal contrast. according to some estimates I made much earlier, the time to get that contrast with agitation of 3 inversions each 30 seconds would have taken about 35 minutes.

It seemed that the obvious next trial would be to add another ml of TEA, which is actually an increase of 33%, but still not much in absolute terms. The result was about the same overall contrast in 30 minutes (I may have said 20 before. That was wrong.), with the lowering of the shadows and the raising of highlights. I did not compare stand development with agitated development. I have some number, but I am going to repeat them before I publish them. The comparison of stand and agitated development, using the same formulation in both cases, will show some interesting results, but that's another hypothesis.

I thought I transmitted a jpeg of my chart, but I can't seem to find it anywhere.

 

[gainer]

I'm going to try to send that chart again. It is only supposed to have about 80 K, so should go alright.

I see I didn't wait long enough. I can only send a picture that is less the 700 X 900, and mine is 800 X 600. Go figure. I'll rotate it 90 degrees and send it in a little while.

 

[Kirk Keyes]

I don't know exactly how to calculate the amount of TEA required to neutralize a gram of ascorbic or erythorbic acid.

Well, I'm not chemistry expert, but without looking at the pKa's of those compounds, the back of the napkin approach would be to figure out the equivalence of each compound and go from there. (Remember all that talk about equivalent weights and buffers in the exercise PE gave earlier?)

The ascorbic acid can donate 1 H+ to react with the negative charge on the amine in the triethanolamine (ROH)3N- (that's supposed to be a negative charge on the shorthand formula for a tri-alcohol amine). So the quick and easy answer is they are equivalents in an acid/base reaction and therefore you use equal normal weights. And since the equivalence is 1 - then your equivalent wieghts are equal to your molecular weights.

So just make sure you have the same number of moles present for each. Of course, a bit more math needs to be done to figure out what the resulting pH will be for a solution like that, but I'm sure you can determine that empirically. You may end up needing to add some sort of a buffer to get the solution in to an appropriate pH range!

Kirk

 

[sanking]

Tom - I'm glad you've enjoyed the thread - me too! And I'm actually excited that one person has already read the info on the scientific method and asked a good question from it! Thanks!

I know you are not trying to hijack this thread, but if you would like to start a thread on the subject of techniques that could be used to make microdensity measurements, I would be happy to join in on it with you.

Kirk

At this point I really would like to see the exchange of messages shifted to the microdensity measurement issue because there is really no practical way, so far as I know, to evaluate findings from empirical tests other than by visual analyis.

Ultimately I think visual analysis is the only thing that really matters, at least when the perpsective is making pictorial photographs, but it would certainly be interesting if some relatively inexpensive method of instrumentation could be found that would allow microdensity measurments.

PE stated in another thread that it was possible to do this with a scanner. I am still waiting for him to describe how this can be done. I do have some very good scanners.

Sandy

 

[Kirk Keyes]

The approach to understanding that I favor is a Statistical DOE (Design Of Experiments). In order to accomplish this I need to make repeatable, quantifiable (and applicable) measurements.

Tom - you are speaking my language! See you in the other thread.

Kirk

 

[gainer]

I'm going to try to send that chart again. It is only supposed to have about 80 K, so should go alright.

I see I didn't wait long enough. I can only send a picture that is less the 700 X 900, and mine is 800 X 600. Go figure. I'll rotate it 90 degrees and send it in a little while.

Here we go. If it goes, you'll have to lie on your side to see it.

 

[Kirk Keyes]

Here we go. If it goes, you'll have to lie on your side to see it.

Thanks - that's interesting. So what happens if you further diminish the TEA - say at 2 mls. I was kind of wondering in the earlier post if you picked pH 8.3 for some reason, or can you go lower?

 

[Ryuji]

I don't really want to get between Ron and Patrick Gainer, but if you are pointing out the difference between hydroquinone and catechol in their respective oxidation reactions and pH change, I should point out that the pH rise is a result of sulfonation reaction of oxidized ketone form (quinone) of the developer. In tanning developers, sulfonation reaction is not the fate of majority of the oxidized molecules because they purposely keep the sulfite level low and allow the diketone forms to react with gelatin to crosslink in situ. Therefore, if you use catechol in place of hydroquinone in regular D-19 or DK-50 type developers, I would expect analogous results will be seen, but if you use drastically low sulfite to limit the rate of sulfonation reaction, the result may very well be different. You will have to find available gelatin sites for hardening and the nature of the crosslinking reaction if you want to know the ultimate byproducts.

From: http://silvergrain.org/Photo-Tech/ascorbate-dev.html
"The oxidation products of hydroquinone (ones that are exhausted after developing reaction) is alkaline. This may accelerate development in the area surrounding areas of intense development reaction. On the other hand, the oxidation products of ascorbates are acids, potentially inhibiting development in areas nearby the site of intense reaction. This means that ascorbates are more desirable when adjacency effect and compensation effect are sought."

You mean this assertion?

That's fine and all, but let's get back to developers like Pyrocat and their possible behavior as the buffer changes concentration.

 

[gainer]

Thanks - that's interesting. So what happens if you further diminish the TEA - say at 2 mls. I was kind of wondering in the earlier post if you picked pH 8.3 for some reason, or can you go lower?

It was a bit arbitrary. There are 2 grams of erythorbic acid in 20 ml of the stock. Although amidol is reputed to develop in acidic pH, there are only 0.02 grams of it in the 20 ml of stock. That much amidol in a liter of even neutral pH would not develop very quickly. As it is, with 3 g/l of TEA, standing for 40 minutes at 75 degree just gives about normal contrast. I'll give it a try, but I have a feeling my newborn greatgrandchild would have children before my heirs found density on that film.

The pH of a saturated solution of sodium ascorbate, according to Merck, is 7.6. I don't know what the pH might be of a solution of whatever compound results when TEA and ascorbic or erythorbic acid are mixed in water. If someone would tell me how many moles of TEA it takes to form this compound withone mole of ascorbic or erythorbic acid, I will start with that ratio.

 

[Kirk Keyes]

If someone would tell me how many moles of TEA it takes to form this compound withone mole of ascorbic or erythorbic acid, I will start with that ratio.

I thought you just said you had a Merck Index? Well, anyway, see:
http://environmentalchemistry.com/yogi/chemistry/MolarityMolalityNormality.html
and/or
http://www.sas.org/E-Bulletin/2002-02-01/labNotes2/body.html

 

[gainer]

I thought you just said you had a Merck Index? Well, anyway, see:
http://environmentalchemistry.com/yogi/chemistry/MolarityMolalityNormality.html
and/or
http://www.sas.org/E-Bulletin/2002-02-01/labNotes2/body.html

Nope. When I want to use it I must go to the local college library.
Anyway, I measured a gram of erythorbic acid into some distilled water and found that 1 ml of my 99 % TEA brings pH slightly above 7. The indicator I have has a range of 6.8 to 8.6. When I used 1 ml of TEA with 10 ml of stock in 250 ml of water I got usable density in 16 minutes of standing at 75 F. That is double everything over what I used to get 40 minutes. There are still mysteries. Needless to say I am going to do the whole series over when I've had some sleep and other activity.
I will look up the references you gave.

 

[gainer]

I will look up the references you gave.

I did. I know all that stuff. Dow gives the molecular weight of TEA, and I can see that TEA is ammonia with ethanol molecules in place of the hydrogen. Is each of those forming something akin to ethyl ascorbate? maybe I can work backwards from my little experiment an get an idea.What in the world would you call that compound, anyway?

 

[Kirk Keyes]

I did. I know all that stuff. Dow gives the molecular weight of TEA, and I can see that TEA is ammonia with ethanol molecules in place of the hydrogen. Is each of those forming something akin to ethyl ascorbate? maybe I can work backwards from my little experiment an get an idea.What in the world would you call that compound, anyway?

Ethyl ascorbate is what's called an ester. To make an ester you start with an alcohol and an carboxylic acid in a mineral acid solution. The two combine to form and ester. See: http://wyk.edu.hk/~paulsiu/Chemistry/ester.htm for the genreal reaction.

While the TEA looks like 3 alcohols hooked onto a nitrogen, it's the nitrogen that really takes the primary role in it's reactions. It's better to think of it as an ammonia that has had some of the hydrogens (in the case of TEA, all of them) replaced with something else. So TEA behaves very similar to ammonia.

That's why in a previous post I wrote this out for you:
"The ascorbic acid can donate 1 H+ to react with the negative charge on the amine in the triethanolamine (ROH)3N- (that's supposed to be a negative charge on the shorthand formula for a tri-alcohol amine). So the quick and easy answer is they are equivalents in an acid/base reaction and therefore you use equal normal weights. And since the equivalence is 1 - then your equivalent wieghts are equal to your molecular weights."

Anyway - I guess that wasn't enough.. Here's some more detail then -

The nitrogen in TEA has an electronegative charge, so it will grab onto H+ in acid solutions. It can then make acid salts, such as triethanolamine hydrochloride with solutions of hydrochloric acid. It's not a covalently bonded compound, but ionically bonded. In solution, expect this to behave like ionic compounds - the positive and negative sides of the compound will dissolve into the water than then float around independantly of each other...

With that info in mind, as the ascorbic acid dissolves into solution, it will liberate hydrogen ions. As you titrate with the TEA, the TEA will grab any of the H+ that was floating around free in the solution, and that the ascorbate ion would also just then be floating around as well. Only when they were crystallized or precipitated out of solution would they actually form a "compound", and I would expect that compound to be called triethanolamine ascorbate.

Infact, that is why TEA makes a basic solution when it is mixed with water. Think of water as a hydrogen ion (H+) and a hydroxide ion (OH-) that are ionically bonded to each other. When the TEA gets into solution, it will pull the H+ "away" from an OH-, and then you have the TEA ionically bonded to the H+ now, and some OH- floating around in solution because of that. It's the OH- that is now floating around that makes a solution of TEA dissolved in water basic.

It's just a simple acid-base reaction.

 

[gainer]

Ethyl ascorbate is what's called an ester. To make an ester you start with an alcohol and an carboxylic acid in a mineral acid solution. The two combine to form and ester. See: http://wyk.edu.hk/~paulsiu/Chemistry/ester.htm for the genreal reaction.

While the TEA looks like 3 alcohols hooked onto a nitrogen, it's the nitrogen that really takes the primary role in it's reactions. It's better to think of it as an ammonia that has had some of the hydrogens (in the case of TEA, all of them) replaced with something else. So TEA behaves very similar to ammonia.

That's why in a previous post I wrote this out for you:
"The ascorbic acid can donate 1 H+ to react with the negative charge on the amine in the triethanolamine (ROH)3N- (that's supposed to be a negative charge on the shorthand formula for a tri-alcohol amine). So the quick and easy answer is they are equivalents in an acid/base reaction and therefore you use equal normal weights. And since the equivalence is 1 - then your equivalent wieghts are equal to your molecular weights."

Anyway - I guess that wasn't enough.. Here's some more detail then -

The nitrogen in TEA has an electronegative charge, so it will grab onto H+ in acid solutions. It can then make acid salts, such as triethanolamine hydrochloride with solutions of hydrochloric acid. It's not a covalently bonded compound, but ionically bonded. In solution, expect this to behave like ionic compounds - the positive and negative sides of the compound will dissolve into the water than then float around independantly of each other...

With that info in mind, as the ascorbic acid dissolves into solution, it will liberate hydrogen ions. As you titrate with the TEA, the TEA will grab any of the H+ that was floating around free in the solution, and that the ascorbate ion would also just then be floating around as well. Only when they were crystallized or precipitated out of solution would they actually form a "compound", and I would expect that compound to be called triethanolamine ascorbate.

Infact, that is why TEA makes a basic solution when it is mixed with water. Think of water as a hydrogen ion (H+) and a hydroxide ion (OH-) that are ionically bonded to each other. When the TEA gets into solution, it will pull the H+ "away" from an OH-, and then you have the TEA ionically bonded to the H+ now, and some OH- floating around in solution because of that. It's the OH- that is now floating around that makes a solution of TEA dissolved in water basic.

It's just a simple acid-base reaction.

Thanks. The Dow site says the the ethanolamones can form esters. One way or the other, 2 g/l works as shown in the updated chart. It is a little better at compensating than 3 g/l. The shadows are practically the same while the highlights are lower, but there is not the flattening seen with amny compensating developers, at least within the range of my step density wedge.

 

[gainer]

This is from the Dow site:
Dow’s versatile family of ethanolamines — including monoethanolamine (MEA),
diethanolamine (DEA), and triethanolamine (TEA) — offers a broad spectrum of application opportunities. Triethanolamine is available as TEA, 99% and TEA, Commercial (which contains nominally 15% diethanolamine). Because ethanolamines combine the properties of amines and alcohols, they exhibit the unique capability of undergoing reactions common to both groups. As amines, they are mildly alkaline and react with acids to form salts or soaps. As alcohols, they are hygroscopic and can be esterified.

 

[Ryuji]

Ascorbates actually undergo several other kinds of esterification reactions. Borates and phosphates are known. However, all of these esterified ascorbates no longer satisfy the structure of HO-C=C-OH so they are no longer developing agents, unless the ester is hydrolized.

Triethanolamine also undergo esterification reactions as it has primary alcohols available for reaction. Therefore, esterification of ascorbate in TEA solution is a very difficult approach, even if it is potentially useful in preparing a stock solution of long shelf life.

 

[Ryuji]

Like most other things, that ethanolamines form esters is a VERY common, basic knowledge of organic chemistry. But don't worry, in your developer solution, it is not happening. They have nothing to form esters with.

Thanks. The Dow site says the the ethanolamones can form esters. One way or the other, 2 g/l works as shown in the updated chart. It is a little better at compensating than 3 g/l. The shadows are practically the same while the highlights are lower, but there is not the flattening seen with amny compensating developers, at least within the range of my step density wedge.

 

[Kirk Keyes]

Like most other things, that ethanolamines form esters is a VERY common, basic knowledge of organic chemistry. But don't worry, in your developer solution, it is not happening. They have nothing to form esters with.

Ryuji - thanks for the extra info - but yeah, I was trying to keep things more relavent to Pat's developer solution to keep my relpy simpler.

 

[gainer]

Ryuji - thanks for the extra info - but yeah, I was trying to keep things more relavent to Pat's developer solution to keep my relpy simpler.

Yeah, right. So do I have to ask if I have true compensation?

 

[gainer]

The legends on my chart should be ml/l instead of g/l. Grams per liter would be about 1.13 times those numbers.