How many times?

#1

How many times can a jar of oxalic or citric be used before it is "spent". Does the change in color (to olive green) indicate a change in chemical makeup?

#2

For Oxalic, I'll usually soak cans for a few hours and take the good ones out, and leave the mysterys in overnight. I never re-use acid. I always mix up a new batch. The used stuff has mud and rust in it and why bother. I've tried Citric and it ate holes in a yellow Brown Derby OI from the inside out. Anyone who has dumped in the West, knows Brown Derby OIs are indestructable and can survive an atom bomb blast but citric acid ruined it! And it takes to long to see results. I wont ever use it again but that's just my opinion.

#3

i agree with everything ed said except sometimes i will use old acid for one thing. if i have some really cruddy rusty mystery cans ill put them in the old acid just so it will remove a little to identify cans to see if they are worthy of a good batch of acid.
mike