The Effect of Temperature on the Luminosity of Radium Compounds

Effect of temperature on the luminosity of RaBr₂ and of mixtures with BaBr₂.---(1) In the case of pure RaBr₂, a tube containing 9 mg after heating to 600^∘{}C gave an initial luminosity of 5600^∘{} μ-candles/cm² which decreased in 1 hr to 3600 or 2800 according as the tube was cooled to 20^∘{} suddenly or gradually, and continued to decrease, according to the equation Iₜ=I_∞+I₀e^-At⁶⁷, reaching an equilibrium value of only 6{μ}-c/cm² after 500 hours. This equilibrium value increases somewhat with the temperature but depends only on the temperature and not on the previous treatment. (2) In the case of mixtures with BaBr₂, the initial luminosity after removing from the furnace increases exponentially with the temperature; the rate of decay is greater the lower the temperature at which the sample is held; the equilibrium luminosity for 1 to 3 per cent RaBr₂ at 20^∘{} increases markedly as the radium content decreases and for higher temperatures decreases as the temperature is increased. For 7 per cent RaBr₂, however, the equilibrium luminosity at 20^∘{} is less than for either 3 or 100 per cent, and it increases with the temperature. In all cases, however, the equilibrium value depends only on the composition and on the temperature at which it is kept. These results are consistent with the suggestions by Rutherford of the formation of "active centers."