Glycin shelf life

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I went to buy some Glycin at my photo shop, but noticed it was a brown colour, a bit like milk chocolate. I was advised that it was still ok, and only when it turns very dark brown should it be discarded. I vaguely recall reading somewhere on www.unblinkingeye.com (?) that even when light brown in colour it is no longer usable, so I didn't buy any. The Merck Index of pharmaceuticals says that Glycin will darken over time but does not say that it changes its chemical structure or degrades. Does anyone have any definitive advice about the shelf live of Glycin and what the change in colour actually means?

thanks

-- George Paltoglou (stellar@optusnet.com.au), November 23, 2001

Answers

Fresh Glycin should be a light golden colour. Pale yellowy brown. (I've got some here of unknown age that's the colour of well-tanned caucasian skin, and it's still OK.)
Any darkening is due to oxidation, and means that some of the reducing power of the developing agent has gone. You can compensate by using more in the formula, but how much more would be a matter of trial and error.
All developing agents are reducers, meaning they readily combine with oxygen, and halides, to 'reduce' metallic compounds to pure metals. This also means that they're susceptible to absorbing oxygen from the air, and rendering themselves useless over time. Some agents need to be in solution to work effectively, and these ones keep well in dry form. Phenidone and Hydroquinone have a very good shelf life. Metol and Glycin keep moderately well, while Amidol, Pyro and Paraminophenol are probably the worst for self-oxidation.

I'd get the shop to give you some sort of warranty that the stuff is still good, or your money back, or you can try to haggle for a bargain price.

-- Pete Andrews (p.l.andrews@bham.ac.uk), November 23, 2001.


The only warranty they were willing to give was "we think its probably still ok"! And I did ask if they would discount it and they offered 10%. Neither of these are sufficient in my view, so I might try and source it through a chemical supplier.

-- George Paltoglou (stellar@optusnet.com.au), November 23, 2001.

I just bought glycin from Photographers Formulary. They supposedly make it up every couple weeks because of the aging issue and were extremely concerned that I use it quickly. We even discussed flooding the top of the bottle with nitrogen or argon to retard oxidation. They ship the bottle in an opaque black plastic bag to keep it out of the light. Color on receipt was a slightly yellowish off-white, but closer to white than anything. OTOH, old literature never mentions special precautions or aging, so I don't know how big an issue it is. I've also read that phenidone doesn't keep terribly well dry, but mine is at least 15 years old and still seems active. Don't ask about my hydroquinone- it's a big Mallinckrodt can dated 1960, but still seems ok in color and potency.

-- Conrad Hoffman (choffman@rpa.net), November 23, 2001.

I bought Glycin from Photographers Formulary in march, and it's still ok with no change in color (light golden brown). When I get potassium carbonate next week I will mix up most of the glycin to a highly concentrated Agfa 8 and fill small 30 ml bottles with it. Each bottle will make 500 ml working solution.

-- Patric (jenspatric@mail.bip.net), November 23, 2001.

I don't know much about glycin, but it is a key component to my particular process.

I develop my Neopan 400 and Tmax 100 in PF FX-2, and Glycin is present in the mixture part A. The one and only time I have ordered this solution, I got 4 kits, 3 of them looked as though they had been at least packaged at the same time, with similiar labels, etc. The fourth looked older, due to faded packaging and streaky shrink wrap. I mixed this one first. In the kit contains a 15gm black bag of Glycin. It had a tannish color. Mixes hard. (BTW- if someone has a method for dissolving glycin w/o alcohol, please let me know.)

FX-2 also contains metol as a developing agent, 5gm in pt.A.

I haven't really experienced any shift in going from old to newer kits, so I assume it shouldn't matter.

Hope this helps.

-- Mike DeVoue (karma77@att.net), November 23, 2001.



I have no problems with dissolving glycin when I mix Agfa 8.

-- Patric (jenspatric@mail.bip.net), November 24, 2001.

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