ABSTRACT
This chapter explores a balance method described for accurately comparing quantities of radium by their γ radiation, in which the ionisation due to the γ rays is balanced against the constant ionisation due to uranium oxide. The balance method was employed to determine the period of transformation of the radium emanation. In making a comparison, it is essential to know that the radium compound contains only radium and its products and no meso-thorium or radio-thorium. The γ activity of radium preparations has been usually compared by electroscopic methods. The electroscope is either composed of lead plate about 3 mm thick or is completely surrounded by a lead cover of this thickness. The decay of the γ ray activity of a large quantity of emanation was determined over several weeks by the balance method. It was found that the γ ray activity of a radium preparation was not appreciably altered by exposure in a strong magnetic field.
