Old hydroquinone. How to test it?

norm123 · Feb 1, 2018

Hi
I have an old jar of hydroquinone. I don't know how old, maybe 30 years. I bought this from a guy and it was 2/3 full.
Is there something to do to know if this hydroquinone is good....alone. Sure I can do maybe a D-76 recipe with all stuff but I prefer, if possible, to test the hydroquinone alone.

Give me some suggestions.

Regards
Norm

BradS · Feb 1, 2018

I have a jar of Kodak branded hydroquinone from ca. 1974. It has turned a little grey-ish in color but still seems to work ok. I think that if it turns brown, it has gone bad.

Not much help, I know but I’m interested to know too.

newcan1 · Feb 1, 2018

I am still using stuff from the 1950's.

Gerald C Koch · Feb 1, 2018

BradS said:
I have a jar of Kodak branded hydroquinone from ca. 1974. It has turned a little grey-ish in color but still seems to work ok. I think that if it turns brown, it has gone bad.

Not much help, I know but I’m interested to know too.

+1

Besides grey it can also be purple or light tan and still be good. Hydroquinone has a VERY long shelf life.

norm123 · Feb 2, 2018

Thank you all for info. I'll try it in some recipies.

Regards

Martin Rickards · Feb 2, 2018

It can be oxidised in air to give benzoquinone but this is readily reduced back to HQ. The only real way to test the purity would be its melting point that should be 172 °C (342 °F). If it's substantially (> 10-15ºC) less be doubtful. Why don't you just make up a batch of D76 to see how it works?

norm123 · Feb 2, 2018

Martin Rickards said:
It can be oxidised in air to give benzoquinone but this is readily reduced back to HQ. The only real way to test the purity would be its melting point that should be 172 °C (342 °F). If it's substantially (> 10-15ºC) less be doubtful. Why don't you just make up a batch of D76 to see how it works?

I'll do.
Thank you

Gerald C Koch · Feb 3, 2018

The book Photographic Chemistry by Pierre Glafkides has a chapter on identifying developing agents. To a solution of the developing agent add a drop of ferric chlorde solution and watch for any color changes. The colors are fairly distinctive. This would tell if the hydroquinone is good.

Old hydroquinone. How to test it?

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