Oxidized metol?

[jaanus20]

I have bought some metol, and it is not a white powder, like I have seen, but a dark gray, with some clumping. Is the metol oxidized and unusable for use in makig film developer?

 

[koraks]

Whether it's usable, I couldn't say, but all the metol I've ever bought was either crystal white or very pale tan. Dark gray and clumped doesn't sound good to me. You could try and mix a test batch of developer and compare that to a known-good developer of the same formulation - if you have the materials to do so.

 

[jaanus20]

It seems the metol has a lot of impurities in it. When mixing up some developer, it was a dark and murky, but passing that through a coffe filter filtered out the black sediment and came out crystal clear and the negatives I got with the developer seems to be ok. It seems the metol has a lot of impurities in it. When mixing up some developer, it was a dark and murky, but passing that through a coffe filter filtered out the black sediment, and the negatives I got with the developer seems to be ok.

 

[koraks]

Yeah, sounds like the developer is just partly oxidized. Not too great, but I wouldn't worry about it.

 

[Raghu Kuvempunagar]

There is a test for purity of metol.

Photo-Miniature : Free Download, Borrow, and Streaming : Internet Archive

Superseded by New Photo-Miniature, q.v

archive.org

 

[bernard_L]

There is a test for purity of metol.



https://archive.org/details/photominiature14newyuoft/page/438/mode/2up?q=pyramidol&view=theater

Interesting, thank you.
Calling chemists: is bichromate (dichromate) ion the key ingredient? Would potassium dichromate work as well?

 

[Raghu Kuvempunagar]

Would potassium dichromate work as well?

It does/will.

 

[retina_restoration]

It may work OK, but in the future, I would suggest finding a different source for your chemistry - Metol should not be dark grey, as this indicates contamination or oxidative degradation, or both. It's possible this Metol will eventually be too compromised to work correctly. I wouldn't rely on it in the long term if I were you.

 

[Nicholas Lindan]

It seems the metol has a lot of impurities in it. When mixing up some developer, it was a dark and murky, but passing that through a coffe filter filtered out the black sediment and came out crystal clear...

That is passing weird. Sounds like metol cut with dirt. If the filtrate is clear then you should be good to go. Assuming, of course, that the substance in question is really metol. Oxidized metol is a purple-brown color and smells bad - but it will often still develop film, kinda. I have never experienced it throwing sediment. It will be interesting to see the results of the dichromate test.

I think the assay above is for a ~2% w/v solution of dichromate.

 

[bernard_L]

I tested my metol from two different sources following the method pointed out above

There is a test for purity of metol.

One from Disactis, white powder, another bought online from Ukraine, (light) gray powder. See below in that order:

Both have a clearly defined edge, and a yellowish center zone. The Ukrainian metol displays a off-white halo when spreading on the blotter paper, maybe related with some impurity alongside the metol (as opposed to a degradation of the metol itself). I Am Not A Chemist.
The Ukrainian stuff I know is functionally OK, performs as expected when in D-23.

 

[drpsilver]

27 Jan 2026

I have bought some metol, and it is not a white powder, like I have seen, but a dark gray, with some clumping. Is the metol oxidized and unusable for use in makig film developer?

Jaanus20:

Try this test, dissolve 1 gm of metol/elon in hot water. I may be very brown. Take 25 gm of sodium sulfite and add it to the metol solution, and stir until fully dissolved. If the solution is still even slightly brown, I would recommend disposing the metal responsibly.

If the solution goes clear, try developing a roll fo film without important images to see how active the developer, and if the negatives look "normal" for your processes.

Regards,
Darwin

 

[relistan]

I tested my metol from two different sources following the method pointed out above

One from Disactis, white powder, another bought online from Ukraine, (light) gray powder. See below in that order:
View attachment 416618View attachment 416619

Both have a clearly defined edge, and a yellowish center zone. The Ukrainian metol displays a off-white halo when spreading on the blotter paper, maybe related with some impurity alongside the metol (as opposed to a degradation of the metol itself). I Am Not A Chemist.
The Ukrainian stuff I know is functionally OK, performs as expected when in D-23.

Nice that you ran the test and thanks for sharing the result!

 

[Raghu Kuvempunagar]

Nice that you ran the test and thanks for sharing the result!

+1

 

[bernard_L]

Fore reference, see below a picture of the two samples of metol.
Further comments:

• Make sure the metol is fully absorbed in the blotting paper before proceeding with the drop of dichromate. Check for the presence of a puddle of liquid, if necessary tilt the paper and wait a little.
• Possibly the actual paper used has an impact on the visual result, like for alt processes; mine was "Buvard Canson" as embossed near the edge.
• For those of us living in civilized countries:
  • 10 grains = 0.65 gram
  • 1 ounce = 30 cm3 (approx)
  • 1/2 dram = 1.35 cm3 (approx)