Quote Originally Posted by Rudeofus View Post
One thing you could do is mix the whole liter, use 500ml for your immediate processing and put the other 500ml into some air tight bottles which you store in some cool place. This way you should be able to use the second 500ml batch a few months later without problems.
The working solution will degrade much more quickly than the liquid stock variations of tetenal you can buy. This is because the water at working solution dilution contains plenty of oxygen to help the chems begin the process of self immolation. I question whether you can get to "several months", but if stored well (glass with no air in contact with the surface of the fluid) it should last at least six weeks. My working solution is older than that, and being used, and is still alive, so I do know there is some cushion built into tetenal's estimated life expectancy of working solution. (My kit says 6 weeks for working solution.)

That said, I'd caution you to do a test before developing something critical with chems that are past their expected shelf life, and brew some new soup if the tests show degraded performance.