Page:Radio-activity.djvu/587

    analysis of α ray curves, 377
    α ray curves of, 378
    β ray curves of, 379
    analysis of β ray curves, 381
    equations of activity curves, 389
    effect of temperature on, 390
    volatility of, 391
    of slow transformation, 311, 397
    variation of α ray activity of, 398
    variation of β ray activity of, 399
    separation of constituents of, 401 et seq. successive products in, 402 variation of activity of, for long periods, 407 presence in old radium, 408 effect of, on variation of activity of radium with time, 409 presence in pitchblende, 410 connection with radio-tellurium, 411 connection with polonium, 411, 412 connection with radio-lead, 413 connection of, with radio-active induction, 415 et seq. heat emission of, 425 et seq. use of, to determine number of β particles from radium, 435 use of, as source of α rays, 543 Des Coudres magnetic and electric deviation of α rays, 148 determination of e/m for α rays, 148 Dewar emission of heat from radium in liquid hydrogen, 420 Dewar and Crookes absence of nitrogen spectrum in phosphorescent light of radium at low pressures, 206 Dewar and Curie production of helium by radium, 479 Dielectrics condition of, under radium rays, 209 Diffusion of ions, 51 et seq of radium emanation into gases, 270 of thorium emanation into gases, 275 of radium emanation into liquids, 276 Discharge action of rays on spark and electrodeless, 208 Disintegration account of theory of, 234, 325, 445 list of products of, 449 rate of, in radio-elements, 457 emission of energy in consequence of, 474 et seq. helium a product of, 476 et seq. possible causes of, 486 et seq. of matter in general, 496 et seq.

Dissipation of charge
  in caves and cellars, 514 et seq. in closed vessels, 531 effect of pressure and nature of gas on, 534 et seq. effect of material of vessel on, 536 et seq.

Dolezalek
  electrometer, construction of, 94 et seq.

Dorn
  charge carried by β rays, 122
  electrostatic deflection of β rays from radium, 124
  discovery of radium emanation, 246
  effect of moisture on emanating power of thorium, 255
  electrolysis of radium solution, 313
  loss of weight of radium, 474
  radium emanation in springs, 513

Dreyer and Salomonsen
  coloration of quartz by radium rays, 213

Dunston
  analysis of thorianite, 486

Durack
  ionization by collision of electrons of great velocity, 171

Dust
  effect of, on recombination of ions, 42
  effect of, on distribution of excited activity, 305


Earth
  amount of radium in, 493 et seq.
  age of, 496
  excited activity deposited on, 504
  activity concentrated on peaks of, 504
  emanation from, 507
  very penetrating radiation from, 520

Ebert
  condensation of emanation from the earth, 510
  apparatus for determining number of ions per c.c. in air, 527
  velocity of ions in air, 528

Ebert and Ewers
  emanation from the earth, 508

Electrolysis
  separation of radio-tellurium by, 25
  of solutions of active deposit, 313
  of radium solutions, 313
  of thorium solutions, 314

Electrometer
  description of, 90 et seq.
  use of, in measurements, 90
  construction of, 91 et seq.
  Dolezalek, 94