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Superseded by New Photo-Miniature, q.v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.