Radium components: compounds of barium, which gave a brilliant green flame color, and unknown radioactive compounds which gave carmine spectral lines that had never been documented before. The Curies found the radioactive compounds to be very similar to the barium compounds, except that they were more insoluble. This made it possible for the Curies to separate out the radioactive compounds and discover a new element in them. The Curies announced their discovery to the French Academy of Sciences on 26 December 1898. The naming of radium dates to about 1899, from the French word "radium", formed in Modern Latin from "radius"
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