Page:Radio-activity.djvu/598

 Scintillations discovery of, in zinc sulphide screen, 158 connection of, with α rays, 158 illustration of, by spinthariscope, 158 cause of, 160 production of, by action of electric field, 160

Searle apparent mass of moving charged body, 71, 127

Secondary rays examination of, by photographic method, 187 examination of, by electrical method, 188 production of, by β and γ rays, 189 et seq.  from different materials, 191   amount of, depends upon atomic weight, 192   magnetic deflection of, 193  Seitz   absorption of electrons by matter, 137 et seq.

Selenium action of radium rays on, 208

Simon value of e/m for cathode rays, 75, 129 Simpson   amount of excited activity in north of Norway, 519  Slater, Miss   effect of temperature on active deposit of thorium, 354  Smolan, Beattie and Kelvin   discharging power of uranium rays, 7  Snow   radio-activity of, 506   decay of activity of, 507  Soddy   comparison of photographic and electrical action of uranium rays, 83   nature of rays from Ur X, 347   production of radium from uranium, 463  Soddy and Ramsay   evolution of gas from radium, 215   production of hydrogen and oxygen from radium, 215   chemical nature of the emanation, 268   gaseous nature of the emanation, 268   volume of the emanation, and change with time, 289   helium from radium emanation, 291   amount of helium produced by radium, 480  Soddy and Rutherford   separation of Th X, 220   decay of activity of Th X, 221   recovery of activity of thorium freed from Th X, 221   decay of activity of Ur X, 223   recovery of activity of uranium freed from Ur X, 223   explanation of decay and recovery curves, 224   rate of production of Th X, 227   theory of decay of activity, 229   influence of conditions on rate of decay and recovery of activity, 233   disintegration hypothesis, 234   decay of activity of radium emanation, 247   measurements of emanating power, 254   effect of temperature, moisture, and solution, on emanating power, 255   regeneration of emanating power, 256   constant rate of production of emanation of radium and thorium, 257   source of thorium emanation, 261   radiations from the emanation, 264   chemical nature of emanation, 267   condensation of emanations of radium and thorium, 277   temperature of condensation of emanation, 278   effect of successive precipitations on activity of thorium, 358   recovery of activity of radium, 372   theory of radio-activity, 439   theory of radio-active change, 445   conservation of radio-activity, 469  Soil   radio-activity of, 507 et seq.   difference in activity of, 508 et seq.

Solution coloration of, by radium, 15 of active deposit in acids, 312 electrolysis of active, 313

Source of thorium emanation, 261 of radium and actinium emanations, 263

Spark action of radium rays on, 208

Spectrum spark spectrum of radium, 15, 16 flame spectrum of radium, 17 effect of a magnetic field on spectrum of radium, 17 of polonium, 23 of phosphorescent light of radium bromide, 206 of emanation, 292 of helium in radium gases and emanation, 477