The radium content of sea‐salt specimens collected on cruise IV of the Carnegie

The following is an account of an investigation which was carried out in the laboratory of the Department of Terrestrial Magnetism at Washington to determine the amount of radium in some samples of sea salt collected by the Carnegie in the Atlantic and Pacific oceans, 1915–1917. 1 The method of investigation was that first used by Joly and described by him in volume 32 of the Philosophical Magazine , 1911. The sea salt was mixed with two to three times its weight of a fusion mixture of sodium and potassium carbonates, and this mixture was heated to about 1,000°C. in an electric furnace. At this temperature carbon dioxide bubbled off from the mixture and presumably carried with it any radium emanation previously present in the mixture.