XXIV CONTENTS 



628. Thorium family; potassium, rubidium 519 



629. Radioactivity units 520 



630. Miscellaneous radioactivity constants 521 



631. Relative phosphorescence excited by radium 521 



632. Vapor pressure of the radium emanation in cm of mercury .... 521 



633. Alpha particles : Range, velocity, ionization 522 



634. Relative ranges of, of RaF in gases 523 



635. " " " " " " RaC in solid elements . . 523 

 635(a). " , long-range [from RaC and ThC']. Relative 



numbers 523 



636. Alpha particles: Atomic stopping powers for, of RaC 523 



6y/. Stopping powers of molecules for, of RaC . . 523 



638. H particles 524 



639. Relative total ionization by a rays in various gases 525 



640. Delta rays 525 



641. Heating effect of radium and its emanation 525 



642. Beta rays 526 



643. " particles, work of extraction of 527 



644. " from RaE, effective range of, in a few elements . . 528 



645. " absorption of, in air and C0 2 528 



646. Gamma rays : Emission, energy and wave length, etc 529 



647. " Nuclear analysis, ionization 530 



648. " Scattering, comparison of sources 531 



649. " Absorption of 532 



650. Characteristic gamma rays, wave lengths and energies 533 



651. Gamma rays: Nuclear energy from spectra 533 



652. " Wave lengths and energies by crystal reflection . . 534 

 ^53* Quantities in radioactive equilibrium 535 



Rontgen Rays (X Rays) 



654. Cathode rays 536 



655. Constants for cathode-ray speeds in matter 537 



656. X-ray emission 537 



657. Emission lines and critical absorption limits (in Angstroms) . . . 538 



658. Probabilities of ionization in K and L shells 541 



659. Energy and efficiency of production of characteristic X rays . . . 542 



660. Energy and quality of emission X rays 542 



661. X-ray spectroscopy 543 



662. Lattice constants of crystals 543 



663. Absorption and scattering of X rays ; fluorescence 543 



664. X-ray absorption and chemical combination 544 



665. Mass absorption coefficients, fx/p 545 



666. Photographic effects of X rays 546 



