ABSTRACT
The total number of a particles expelled per second from one gram, of radium has been estimated by measuring experimentally the total positive charge carried by the a rays from a thin film of radium, on the assumption that each a particle has the same charge as an ion produced in gases. With very sensitive apparatus, it should be just possible to detect the ionization produced by a single a particle by electrical methods. By counting at intervals the number of particles expelled per minute, we have been able to obtain the curves of decay of activity of a plate coated with radium C or actinium B. The time interval between the entrance of successive a particles has been observed over a long interval, and the results show that the distribution curve with time is similar in general shape to the probability curve of distribution of the velocity of molecules in a gas.
