bo, i think the chlorine gas is produced much too slow in a mixture of hcl/mno4 in order not to get lost through minimal rifts in your reaction devices and thus never reaching an appropriate pressure. is this the reason why you've got to use something like an aerator? anyway, how long does it take until ca 100ml of hcl and, say, 3 grams of mno4 have been fully reacted?
@xxx: do you know the chlorinating tabs for swimming pools? i guess they'd also work. anyone attempted this?