Page:Radio-activity.djvu/584

 comparison of absorption of α rays from radio-elements, 164 diffusion of radium emanation, 270 decay of excited activity from radium, 306

Bumstead presence of thorium emanation in atmosphere, 512

Bumstead and Wheeler diffusion of radium emanation, 273 emanation from surface water and the soil, 512, 522 identity of emanation from soil with radium emanation, 512, 522

Burton radium emanation in petroleum, 516

Burton and McLennan penetrating radiation from the earth, 520 radio-activity of ordinary materials, 537 emanation from ordinary matter, 538

Campbell radio-activity of ordinary materials, 540

Canal rays discovery of, 78 magnetic and electric deflection of, 78 value of e/m for, 78  similarity of, to α rays, 110  Capacity   of electroscopes, 87   of electrometers, 94, 102   standards of, 102  Carbonic acid   radio-activity of natural, 516  Caspari and Aschkinass   action of radium rays on microbes, 216  Cathode rays   discovery of, 73   magnetic and electric deflection of, 74   value of e/m for, 75   radiation of energy from, 79   comparison of, with β rays, 120   absorption of, by matter, 136, 137   see also β rays  Caves   radio-active matter present in air of, 514 et seq.   radio-activity of air of, due to emanation from the soil, 515  Changes   (see Transformations)  Charge   carried by the ions, 50 et seq.   negative charge carried by β rays, 120   measurement of charge carried by β rays, 121 et seq.   positive charge carried by α rays, 145   measurement of charge carried by α rays, 151 et seq.

Chemical nature of emanation, 267 of active deposit, 312

Chemical actions of radium rays production of ozone, 213 coloration of glass and rock-salt, 213 on phosphorus, 214 on iodoform, 214 on globulin, 214 evolution of hydrogen and oxygen, 215

Child potential gradient between electrodes, 65 variation of current with voltage for surface ionization, 66

Clouds formation of, by condensation of water round ions, 46 et seq. difference between positive and negative ions in formation of, 49

Collie and Ramsay spectrum of emanation, 292

Collision ionization by, 39, 57 number of ions produced by β rays per cm. of path, 434 total number of ions produced by collisions of α particles, 434

Coloration of crystals of radiferous barium, 15 of bunsen flame by radium, 15 of glass by radium rays, 213 of rock-salt, fluor-spar and potassium sulphate by radium rays, 213

Concentration of excited activity on negative electrode, 297 activity of radium independent of, 466

Condensation of water round the ions, 46 et seq. of emanations, 277 experimental illustration of, 279 temperature of, 280 difference between point of, for emanations of thorium and radium, 283 from air sucked up from the earth, 510

Conductivity of gases exposed to radiations, 31 et seq. variation of, with pressure, 61 et seq. variation of, with nature of gas, 64 comparison of, for gases exposed to α, β, and γ rays, 64