Page:Radio-activity.djvu/582

  possible connection with radio-activity of thorium, 28
  emanation from, 249
  excited activity produced by, 311
  effect of magnetic field on excited activity from, 324
  separation of actinium X, 365
  decay of actinium X, 365
  source of actinium emanation, 365
  analysis of active deposit of, 366
  radiations from products of, 368
  penetrating power of β and γ rays from, 368
  products of, 369
  table of products of, 449
  possible origin of, 464

Actinium A
  separation and period of, 367 et seq.

Actinium B
  period of, 368
  properties of, 368

Actinium X
  separation and decay of, 364 et seq. production of emanation by, 365 Adams decay of activity of emanation from well water, 511 decay of excited activity from the emanation, 511 Age of radium, 457 of sun and earth, 492 et seq.

Allan, S. J.
  increase with time of excited activity from atmosphere, 505
  radio-activity of snow, 506
  effect of conditions on decay of activity from air, 519, 523

Allan and Rutherford
  decay of excited activity from the atmosphere, 503
  ionization of air in closed vessels, 534

Allen, H. S. and Lord Blythswood
  radium emanation in Bath springs, 513

Anderson and Hardy
  action of radium rays on the eye, 217

Armstrong and Lowry
  radio-activity and phosphorescence, 444

Arnold
  rays from phosphorescent substances, 4

Aschkinass and Caspari
  action of radium rays on microbes, 216

Atmosphere
  excited activity from, 501 et seq.
  radio-activity of, due to emanations, 504
  diffusion of emanations into, from the earth, 507
  effect of temperature, pressure, &c. on radio-activity of, 517 et seq.
  presence of very penetrating radiation in, 520
  comparison of radio-activity of, with radio-elements, 521 et seq.
  amount of radium emanation in, 524 et seq.
  ionization of, due to radium emanation, 526

Atom
  number of per c.c., 54
  disintegration of, 234 et seq.
  complex nature of, 235
  changing atoms, 444 et seq.
  possible causes of disintegration of, 486
  evolution of, 496

Atomic weight
  of radium by chemical methods, 17
  from spectroscopic evidence, 18
  emanations, 273
  of radio-elements and connection with radio-activity, 445


β rays
  discovery of, 113
  magnetic deflection of, 114
  complexity of, 116
  examination by the electrical method, 118
  effect of, on a fluorescent screen, 119
  charge carried by the, 120 et seq.
  electrostatic deviation of, 124
  velocity of, and value of e/m for, 126
  variation of e/m with velocity of, 127 et seq.
  distribution of velocity amongst β particles, 131
  absorption of, 134 et seq.
  variation of absorption with density, 136 et seq.
  number of β particles stopped by matter, 137 et seq.
  variation of intensity of, with thickness of layer, 140
  secondary β rays, 189 et seq.
  relative ionization produced by α and β rays, 196
  relative energy emitted in form of α and β rays, 196 et seq.
  phosphorescent action of, 201 et seq.
  physical action produced by, 207 et seq.
  chemical action of, 213
  physiological action of, 216
  from Ur X, 347