Doug,

I agree with you about chlorine and iodine being used to disinfect water, but surely there are concentrations beyond which the water becomes unsafe to drink.

Potable Aqua, for example, has a dosage of 2 tablets per quart of water, or 1 tablet per pint (sandwich bag amount). If you were to try to disinfect half a pint with a single tablet, you would have twice the required concentration of iodine. Is there not a point at which the concentration becomes toxic, or affects your digestive system as I described earlier?