However, you really need to be careful using this as such a small amount goes a long way. It's really dangerous if you don't know what you're doing. It also requires a nice set of scales with accuracy down to the milligram. The vast majority of us don't even know what a set of scales like this look like. This whole subject of chlorine in the water supply is hotly debated, however.
Many people feel that any chlorine at all in their water is very BAD as it is a poison.
Obviously, the nation's water-works experts disagree and we could argue about this forever. But there is a solution. Chlorine is a non-persistent agent in water and quickly dissipates out of the water if left uncovered. Pouring the water back and fourth between two containers will greatly decrease the time it takes for this to happen. The more heavily contaminated the water is, the more chlorine it will take to get the job done.