Kps of silver halides

[Photo Engineer]

T = temp in C and t = temp in K IIRC. It has been a while. I'll have to review some more of my old (20+ years ago) notes.

Z0 = 371.42
Z1 = (Z1X - 23.41 * kfraction) * exhal + (21.33 - 23.41 * kfraction) * NO3CONC
Z2 = (Z2X - 23.41 * kfraction) * exhal + (121.55 - 23.41 * kfraction) * NO3CONC

PE

 

[mghis]

Thank you! Could you define also Z1X, Z2X, kfraction, and exhal? I imagine that NO3CONC is nitrate concentration of salt bridge (isn't it?).

I'm sorry that I keep bothering you, but this kind of information is not easily available on textbook and scientific articles. I can only imagine how many hours of experiments and tinkering was needed to get right each of your equations.

 

[Photo Engineer]

Kfraction is the offset for the presence of Potassium ion (the basic assumption is Sodium ion), and exhal is the excess halide present at any instance. NO3CONC is the Nitrate ion concentration in the precipitation solution at any instant. In effect, these are corrections for Ionic Strength. There are also corrections for Ammonium Ion and for Gelatin.

As for the Z values, I cannot find further reference to them at this time. After all, the last time I looked at this was over 20 years ago.

PE

 

[Photo Engineer]

Hah, I remembered something.

These Z values are the approximate offsets for the ionic strengths on the Junction Potential via the PKSPs.

Does that help?

PE

 

[mghis]

Yes, thanks! Well, putting NO3CONC = 0 and Kfraction = 0 (as is in the KEDS screenshot) makes things a bit simpler. I also think that, using screenshot conditions, exhal must be = 0.1. Interesting noting that juncpot goes to infinite as z2 tends to zero. (I think that often taking limits gives some insight in what is going on..) I'll ponder on this...

Do you happen to have something about activity coefficient, which may explain why my results of post #23 are always a bit off?

 

[Photo Engineer]

I have no notes on Activity Coefficient at hand. I would have to do another search and it may take me a few days.

Sorry.

PE

 

[mghis]

Don't worry!
If it's not too much trouble, when you get a chance...

 

[Photo Engineer]

Here is ACTCOEF as we calculated it. As you can see, this is a neverending quest for the variables used and is a far cry from the bare bones in the patent. The patent works fully, don't get me wrong, but for the precision and accuracy we needed and used, we used many many additional variables as I noted above. We often got and used vAg values that were carried out to the 2nd decimal.

gln(1) = ((-tempcoef * Sqr(newionst) / (1 + Sqr(newionst))) + clKBETA * kfraction * ionst + clNABETA * (1 - kfraction) * ionst + clKDELTA * (kfraction * ionst) ^ 1.5 + clNADELTA * ((1 - kfraction) * ionst) ^ 1.5)
gln(2) = ((-tempcoef * Sqr(newionst) / (1 + Sqr(newionst))) + brKBETA * kfraction * ionst + brNABETA * (1 - kfraction) * ionst + brKDELTA * (kfraction * ionst) ^ 1.5 + brNADELTA * ((1 - kfraction) * ionst) ^ 1.5)
gln(3) = ((-tempcoef * Sqr(newionst) / (1 + Sqr(newionst))) + ioKBETA * kfraction * ionst + ioNABETA * (1 - kfraction) * ionst + ioKDELTA * (kfraction * ionst) ^ 1.5 + ioNADELTA * ((1 - kfraction) * ionst) ^ 1.5)

actcoef = cl * Exp(gln(1)) + br * Exp(gln(2)) + io * Exp(gln(3))

And, this now goes to my limit for help. I simply cannot help you much more at this detailed level.

PE

 

[mghis]

Thank you! Yes, this is much more complex that I expected. Well, I'm already happy of having a slight idea of what it is like.

I still have a less technical question. Grain composition varies with depth, if I got it right. For instance there might be an emulsion which is more rich of an halide at the center and of another halide at the surface. I think that solid-solution equilibria happen only at the interface, at the surface of the grain. Does KEDS keep track of whole grain composition and of surface grain composition separately? (I don't ask a quantitative approach, I'm beginning to understand how these things can be complex )

 

[Photo Engineer]

This is a differential equation of the sort dH/dT or Halide vs concentration or dH/dF for Flow rate. Many variables go into this. You can make a core Iodide, with graded interface to pure Bromide, but you have trouble making a pure Bromide core with a graded Iodide surface. With Chloride, things become vaguer. There is a bit more similarity and some solubility problems in the presence of enough Chloride. You see that this is complex and far far beyond the scope of APUG / PHOTOTRIO. The model proceeds as one "runs" the emulsion "making" the emulsion in front of the designer. He/She can then compare it with the result and give us feedback to refine the model. This took place over a period of years developing these equations and then refining them.

PE

 

[Nodda Duma]

Hopefully Kodak will eventually “declssify” their internal detailed research, but I fear it will end up in the dumpster like I’ve seen of so much other corporate knowledge at the various places I’ve worked.

 

[Photo Engineer]

Due to lawsuits, Kodak has a 20 year "hold time" on all documents. Much of the R&D from my time is now totally gone.

PE

 

[mghis]

I'm not familiar with US laws. What is hold time? By "gone" you mean lost? That would be very unfortunate.

 

[Photo Engineer]

In the US, patentable data or research data must be held for a minimum of 20 years. Kodak has a "Records Retention" plan that follows those guidelines. At the end of this time, all data can (and probably is) destroyed. The only thing kept is actual manufacturing formulas on ongoing products.

PE