In using both C-41 and RA-4 chemistry, there is a definite shelf life, which can be extended - a lot - by displacing the oxygen in partially filed containers with an inert gas. JOBO / Tetenal catalogs a product called "Protectran" for this purpose. In trying to get this (comes in a spray can - I have *one* left), I was just informed that it has been discontinued, and I am searching for a suitable sustitute. I know that most of the chemistry manufacturers recommend dry nitrogen. The problem here is a source of dry nitrogen. So far, the only one I've found would be a supplier of industrial gasses - an entire "tank" for $LOTS. Somewhere, I've read that the suppliers of fine wines carry spray cans of argon, for displacing the oxygen in partially filled wine bottles. Anyone here have any knowledge of argon - which I undersatnd is an inert gas - and its probable effects when used to preserve photographic chemistry? Or another suitable replacement for "Protectran" or dry nitrogen?