ABSTRACT
The first systematic measurements of the production of helium by radium were made last year by Sir James Dewar. His experiments indicate that radium in equilibrium produces helium at a constant rate equivalent to 135 cubic mms. per gram per year, a result in fair agreement with the calculated quantity. It has been shown by Ernest Rutherford, Hans Geiger and T. Royds that the α particle emitted by radium and its products is an atom of helium. Another determination has recently been made by the writers using a barium-radium salt containing about 200 milligrams of radium, loaned by the Vienna Academy of Sciences. The salt, chemically treated to remove polonium and radium D, was placed in a platinum capsule which was in turn sealed in an exhausted tube of hard glass. At the end of 83 days, the gases were completely removed by heating and exposed to charcoal cooled in liquid air.
