INVESTIGATION of the visible radiation of certain oxides, with reference to their possible use as illuminants, has extended over a period of more than a century, but few quantitative results have been published.
This work is an investigation of the visible radiation characteristics of various oxides and oxide mixtures when heated by cathode ray bombardment, gas-air and oxy-gas flames, to brightness temperatures (X = 0.665 ~) from about 14oo to 2000 ยฐ K. Ordinary gas-alr burners, equipped with valves regulating the gas pressures, were used in flame heating. The oxides were kept in the oxidizing part of the flame. A cold cathode discharge tube, connected through a long capillary to an oxygen tank, was used in studying the oxides under cathode ray bombardment. The oxide, mounted in a nickel button, served as the anode, and was viewed through a window at the end of a long arm of the tube. With the window thus at some distance from the hot circle the error due to blackening of the tube during operation was greatly reduced.
The oxides investigated were urania, ceria, lanthana, neodymia, erbia, yttria, zirconia, thoria, alumina, beryllia, magnesia, and mixtures of thoria with one per cent. ceria (the Welsbach mantle mixture), one per cent. and less of urania, one per cent. neodymia, and one per cent. manganese oxide.
An optical pyrometric method of observation was used, measurements of the brightness of the oxide under test being made with a disappearing filament type of pyrometer, equipped successively with red (effective X = 0.665 ~) and blue (effective X = o.467 #) screens, from which the red brightness temperature and the ratio of red to blue intensity ratio were determined, and with a combination of red and green screens having an effective wave-length approximately equal to the Crova wave-length, from which the candles emitted per square centimeter of surface were determined.
The oxides used, unless otherwise stated, were in as pure a state as could be obtained, and were either pressed as compactly as possible in a hydraulic press, or fused to insure a