Green Your Kitchen Space - from marthastewart.com
"Unclog Your Sink Naturally
As is, baking soda won't necessarily clear a pathway. It first needs to change its chemical composition. Don't worry, it sounds more complicated than it actually is. Boiling water converts baking soda to sodium carbonate, a more effective drain cleaner. Pour 1 cup of baking soda down the drain, followed by 3 cups of boiling water, and let science take over. It's a much safer choice than commercial drain cleaners, which can harm skin, eyes, lungs, and the water supply."