I've been using some Edwal Hypo Check that is about a hundred years old. When a drop of it in my paper or film fixer turns milky I dump and remix and refix if neccesary. Today I check my film fix before doing some processing. Dang! the EHC turns milky. But I don't think that batch of film fixer has been used all that much so I grab a piece of clipped leader and dip it in the bottle. It clears up in less than a minute. Is anyone aware of an expiration to Hypo Check or should I just cease to trust it altogether?