The "X" in Microdol-X: S. Citrate experimental result

When I have tried the generic metol, sulfite & salt formula for M-X it has always produced dichroic fog with 100TMX.

Ron Mowrey posted that the 'X' for suppressing dichroic fog was sodium citrate: https://www.photrio.com/forum/threads/microdol-x-homebrew-question.110991/page-5#post-2057961

Today I had a roll of exposed 100TMX with not much important on it and no M-X made up, so I thought I'd try it.

The generic Microdol (no -X) formula per liter is:

5g Metol
100g S. Sulfite
30g NaCl (pickling salt)

To this I added:

20g S. Citrate (a trial amount with no justification for quantity)

The result was no dichroic fog.

Disclamers: The moon is waxing gibbous and in the constelation Virgo and this may have something to do with it; And an experimental result that only happened once isn't worth the parchment it is printed on.

michael_r said:

I’ve never seen dichroic fog on TMax 100/400 or other contemporary films from either the home-made/generic Microdol or Ilford Perceptol, which is essentially a packaged version.

Click to expand...

The "Perceptol" formula I have used hasn't shown dichroic fog, although I've possibly only experimented with ILFORD films.

formula:

750ml water
5g Metol
100g Sodium sulphite
30g Sodium chloride
3g Sodium hexametaphosphate - I used distilled water but kept this in for sake of completeness.
Water to make 1000ml

The generic 'Microdol' variants all differ from the disclosed one in a Henn patent from 1945.

5g Metol
100g Sodium Sulfite
12g Ethylene Diamine Sulfate
4g Sodium Metaborate
0.25g Potassium Bromide
20g Sodium Chloride
Water to 1 litre

And it's highly likely to have been adjusted to optimise the buffering, sequestration and resolve any dichroic stain problems. Chlororesorcinol seems to have been added to deal with the dichroic stain that could result from extended exposure to sulfite and (possibly) Metol exhaustion products - Metol apparently produces acutance effects via exhaustion rather than inhibition (phenidones and the iodide & bromide in the emulsion(s) all produce sharpness enhancing inhibition effects), but that shuts down if a source of HQMS or similar is present. Most modern materials have some degree of anti-stain agents incorporated as emulsion addenda.