Sodium Potassium Aluminum Silicate

The U.S. Centers for Disease Control says that potassium iodide pills will keep the thyroid gland from absorbing radioactive iodine.
It cannot protect other parts of the body from radiation.
Side effects can include nausea, upset stomach, rashes, inflammation of the salivary glands and possibly severe allergic reactions. - 482

Sodium hypochlorite is sold in powder form at paint and hardware stores. - 24798