Water-‘absorbing’ agents and drying substances

Any help on this problem would be much appreciated, I really think that chemistry is pretty much the coolest thing in the world. ;) Anyway, for extra-credit, my teacher gives a few of us students some interesting chemical problems every now and then. I am wondering if anyone would be able to help with this one. I need to know of a technique or substance--possibly hydroscopic?--that will react with water but not a halogen in order to form a solid precipitate and/or gas so that much H2O (in the problem, bromide was given as the halogen dissolved) could be then removed from the solution--and yes, it could be anything from arsenic to zirconium (obviously, neither would apply, just saying it doesn’t necessarily have to be extremely common or easy) I have been looking around a bit--could someone just generally explain the principle of drying agents?:eek: I was thinking maybe activated carbon--the solution could be boiled and then run thro...