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