[Since his brother died the day before, Al really hasn't been responding to much of anything on the network. But he has been watching, and he can't in good conscience ignore a question that he can actually answer. His voice is more subdued than usual, but at least no longer cracking.]

It's used for a lot of things, the most common one I know is as part of a combination of chemicals used in photography. I'm not sure why it would be in a medicine bottle, though.