Polonium were marketed by Firestone from 1940 to 1953. While the amount of radiation from the plugs was minuscule and not a threat to the consumer, the benefits of such plugs quickly diminished after approximately a month because of polonium's short half-life and because buildup on the conductors would block the radiation that improved engine performance. (The premise behind the polonium spark plug, as well as Alfred Matthew Hubbard's prototype radium plug that preceded it, was that the radiation would improve ionization of the fuel in the cylinder and thus allow the motor to fire more quickly and efficiently.) Polonium is
Polonium dichloride by dehalogenation of polonium tetrachloride, PoCl. Methods for dehalogenating PoCl include thermal decomposition at 300 °C, reduction of cold, slightly moist PoCl by sulfur dioxide; and heating PoCl in a stream of carbon monoxide or hydrogen sulfide at 150 °C. PoCl dissolves in dilute hydrochloric acid to give a pink solution, which autoxidises to Po(IV). PoCl is rapidly oxidised by hydrogen peroxide or chlorine water. Addition of potassium hydroxide to the pink solution results in a dark brown precipitate – possibly hydrated PoO or Po(OH) – which is rapidly oxidised to Po(IV). With dilute nitric acid, PoCl forms a dark