Yes! You have to have it for baking! It's also good for indigestion, shining silver and copper, and it is one of the ingredients you can use to propel little toy boats. I think the other ingredient might be vinegar..... :?: Makes sense to me, an acid and an alkali..probably have a visible reaction.
Rob, keep that box near the stove. It could save your apartment from fire. I don't think age changes the formula. Or, throw some in the litterbox when you change it, and treat yourself to a new box! I keep one for the fridge and one near the stove for baking, fires, and cleaning my silver jewelry. It's versatile stuff!