Question on Ilford's Wash procedure

[Ryuji]

Hey - you just added that... didn't you? I looked on your page yesterday and I could sear that it wasn't there then...

Yes, I noted that I mistyped the name of one author and I corrected it, together with a bit more additon and editing. Sometimes I think to add something during discussion here... My old static site was not very easy to update but the current system is so easy to update, so I can change the site contents however small, however frequently, when I think about it.

I've been requested to start a semi-routine email list to highlight recent updates to the site. (Although there is RSS/Atom feed for the update info.) I'm considering it. Firefox search plug-in has also been useful for frequent visitors of my site.

I prefer to provide info on places where the information is organized based on the topic rather than random poster preference. Theory or practice of washing or testing for residual chemicals does not change every time someone asks a question on APUG or pure-silver. Nor unknown facts become suddenly discovered because same question get asked many times. So my effort is better spent on building something that is organized.

 

[Kirk Keyes]

Ryuji - do you know of a good source for the N, N-Dimethyl-p-phenylenediamine Sulfate? I think the oxalate salt will work too. I've looked around on the web and not found anyone that looked like they would sell to hobbiests. I have some borohydride and the rest is easy to get.

Ralph - follow the link Ryuji gave above for the method if you are still interested. It looks like everything is there except how to prepare the actual reagents. That's here: http://www.kodak.com/US/plugins/acrobat/en/motion/support/processing/h244/h2404.pdf

 

[Kirk Keyes]

I prefer to provide info on places where the information is organized based on the topic rather than random poster preference.

It's a great site, I really appreciate the work you've put into it.

 

[Tom Hoskinson]

It's a great site, I really appreciate the work you've put into it.

I agree, Ryuji's site is an excellent resource, I use it a lot!

 

[RalphLambrecht]

Thanks Kirk, I appreciate the link.

 

[Ryuji]

Ryuji - do you know of a good source for the N,N-Dimethyl-p-phenylenediamine Sulfate? I think the oxalate salt will work too. I've looked around on the web and not found anyone that looked like they would sell to hobbiests. I have some borohydride and the rest is easy to get.

Sigma-Aldrich, JT Baker, et al. have it. Oxalate may not work well. If sulfate can't be obtained, seek HCl salt, or get free base and dissolve it in HCl or sulfuric acid. Adjust the equivalence of the acid, although I think you'll have to use excess acid and adjust the pH accordingly afterward.

The reason is that, oxalate from the amine can interfare the action of iron in the reaction. It may or may not, but it's safer to stay away from anything known to react with iron, such as oxalate.

The chemistry of methylene blue method is pretty standard trick in analytical chemistry. Analogous test is used for hydrogen sulfide gas or sulfides. Sulfides and N,N-dimethyl-p-phenylenediamine react in the presence of ferric chloride to quantitatively yield methylene blue dye, which can be measured by spectrophotometry.

 

[Ryuji]

Thanks for the nice words.

 

[Kirk Keyes]

The chemistry of methylene blue method is pretty standard trick in analytical chemistry. Analogous test is used for hydrogen sulfide gas or sulfides.

Yeah - I used to do sulfide with that chemistry too. That test sucked to get calibrated as there are no really good sulfide to use as a standard. But one nice thing is that the method allowed you to take a solution of methylene blue and make a secondary standard with it once you had a calibration made from a sulfide solution. We had a pretty concentrated solution of methylene blue for stock - it was really pretty!

I think the method we used started with the oxalate salt, as you dissolve the stuff into sulfuric acid and that would be pretty equivalent to having started with sulfate salt. Perhaps it was easier to dissolve the oxalate than the sulfate. I seem to remember it taking a bit of time to get it dissolved.

And there is a lot of ferric chloride in the solution...

 

[Ryuji]

That test sucked to get calibrated as there are no really good sulfide to use as a standard.

That's the nature of S(-2) chemistry... including residual thiosulfate testing and sulfiding toners. It's best to design system that is very robust and does not rely on tricky conditions. That's like (and, that is) good engineering.

We had a pretty concentrated solution of methylene blue for stock - it was really pretty!

I also use methylene blue for other research as well. I like the combination of neutral red dye and prussian blue pigment. Very beautiful combination!

I think the method we used started with the oxalate salt, as you dissolve the stuff into sulfuric acid and that would be pretty equivalent to having started with sulfate salt.

In that case, as I said, I'd rather begin with free base.

And there is a lot of ferric chloride in the solution...

Well, then you'll need a very good spectrophotometer!

Come to think of it, if you have an array of secondary standard solutions in the standard wells or vials, I think you can use a digital camera for this purpose. Use the right light source and red filter, and watch out for flare. Then write a custom analysis program that loads the raw/tiff file.

 

[Kirk Keyes]

I think you can use a digital camera for this purpose. Use the right light source and red filter

You don't need the red filter, just scrap the blue and green channels. Assuming you have a color digicam, just use the built in Bayer filters.

But your comment does get me thinking about a spectrographic project of mine that has kind of stalled out...

 

[Kirk Keyes]

Well, then you'll need a very good spectrophotometer!

I picked up a nice Spectronic 1201 for home use last year. 20 years old, but works nicely. I was hoping to get a more recent (and much smaller) Spectronic Genesis 5 but prices on those are still more than I was hoping to spend. Anyway, I got something that scans and can be hooked up to the computer. Now I just got to write some macros to control it.

 

[Ryuji]

You don't need the red filter, just scrap the blue and green channels. Assuming you have a color digicam, just use the built in Bayer filters.

But your comment does get me thinking about a spectrographic project of mine that has kind of stalled out...

You said you have a lot of ferric ion in the solution, and the absorption by it may interfere without filtering. You can add the same to the standard solutions and the blanks, but that may reduce the resolution. Or, you could also use a red light source limited to 665nm region (where absorption of methylene blue is maximum). Anyway, using a digicam or maybe even a flatbed scanner with transparency light source (with a suitable well) may drastically increase the measurement efficiency.

I'm curious what's your project?

 

[dancqu]

The rate limiting stage is desorption, especially if
deionized or distilled water is used.

From what you are saying I'd say ion-exchange is
the phenomenon we are dealing with when speaking
of desorption.

BTW, you've mentioned carbonates. I reminded of Agfa's
wash aid recommendation; 2% sodium carbonate. Do you
maintain that a carbonate is the equal of a sulfite
wash aid? If so why are we using a wash aid
which spoils, oxidizes? Dan

 

[Ryuji]

Carbonate is not as good as sulfite for wash aid.

 

[dancqu]

Carbonate is not as good as sulfite for wash aid.

I wonder that Agfa ever recommended carbonate and
for quite some time. Perhaps they found fault with a
sulfite hca's short life span? Perhaps environmental
and allergic reaction concerns? Dan

 

[Ryuji]

I have no relation with AGFA, nor will I argue about it. If you have a question about their things, you are asking a wrong person.

I already made a point on washing aid.