ABSTRACT
The investigation of the radioactivity of thorium, detailed in this chapter arose out of an examination of the power possessed by thorium compounds of giving out a radioactive emanation. In general, a dense crystalline compound in not very fine powder possesses a much higher emanating power than a light floury compound in a much finer state of division. The rate of decay of the emanating power of ThX, and the recovery of this property by the thorium from which it had been separated, were investigated in parallel with the similar experiments on radioactivity already described. It was shown that moisture, the state of aggregation, and temperature influenced the value of the emanating power. The air containing the emanation, obtained in the usual way by passage over thoria, was led through the platinum tube heated electrically to the highest attainable temperature, and also through the tube cooled by solid carbon dioxide and ether.
