Page:Radio-activity.djvu/594

 Oxygen (cont.)  production of, from radium solutions, 215  Ozone   production of, by radium rays, 213   Paraffin   objection to, as an insulator, 96   conductivity of, under radium rays, 210  Paschen   distribution of velocity amongst β particles, 131 et seq.   absence of magnetic deflection of γ rays, 183   γ rays and electrons, 185   heating effect of γ rays, 186, 429  Patterson   number of ions per c.c. in closed vessel, 534   natural conductivity of air due to an easily absorbed radiation, 536   effect of temperature on natural conductivity of air, 536  Peck and Willows   action of radium rays on spark, 208  Pegram   electrolysis of thorium solutions, 314   temporary activity of substances separated from thorium, 415  Penetrating power   comparison of, for α, β and γ rays, 111   variation in, of β rays, 134 et seq.   variation of, with density for β rays, 137   comparison of, for α rays from radio-elements, 164   variation of, with density for α rays, 169   variation of, with density for γ rays, 182  Penetrating radiation   from the earth and atmosphere, 520  Perrin   charge carried by cathode rays, 73   theory of radio-activity, 437  Phosphorescence   production of, by radium, 19   production of, by radium and polonium rays, 201 et seq.   comparison of, produced by α and β rays, 202   of zinc sulphide, 202   of barium platino-cyanide, 203   of willemite and kunzite, 203   produced by radium emanation in substances, 203, 252   diminution of, with time, 205   of radium compounds, 205   spectrum of phosphorescent light of radium bromide, 205   spectrum of phosphorescent light of "emanium," 206   production of by heat (thermo-luminescence), 207   use of, to illustrate condensation of emanations, 279   connection of with ionization, 547 et seq.

Phosphorus action of radium rays on, 214 ionization produced by, 529

Photo-electric action produced by radium rays in certain substances, 214

Photographic method, advantages and disadvantages of, 83 relative photographic action of rays, 83 connection of photographic action with ionization, 546

Physical action of radium rays on sparks, 208 on electrodeless discharge, 208 on selenium, 208 on conductivity of insulators, 209

Physiological action of radium rays production of burns, 216 effect on bacteria, 216 effect on eye, 217

Piezo-électrique of quartz description of, 105

Pitchblendes comparison of radio-activity of, 11 radio-elements separated from, 13 et seq. radium continually produced from, 459 constitution of, 557

Polarization of uranium rays absence of, 7

Polonium methods of separation of, 22 rays from, 23 decay of activity of, 23 discussion of nature of, 24 similarity to radio-tellurium, 26 magnetic deviation of α rays from, 146, 150 slow moving electrons, 153 increase of absorption with thickness of matter traversed, 163 connection of, with radium F, 411

Potential required to produce saturation, 32 et seq. fall of potential needed to produce ions at each collision, 58