I did a search on this but got no definitive results. I've got dry kallitype chemistry from 2013 that I suspected was past its use-by date. So I bought a B&S kit and did some prints with it, but the developer ran out long before the sensitizers. Took a chance and mixed up new dev with the old sodium citrate and it worked fine. Which makes me wonder if the ferric oxalate and the silver nitrate are still good too. All dry powder from Artcraft, stored in original containers. Not stored cool, though they were out of the light and tightly sealed. Any thoughts most welcome.