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Visible radiation characteristics of incandescent oxides
618
CURRENT TOPICS.
]J. F. I.
The Rate of Emission of Alpha Particles from Radium. (Proc. Roy. Soc., A 787.) H . J . J . BRADDICKand H. M. CAve,:. The number of alpha particles emitted by a unit mass of radium in unit time is quite an important constant in the interpretation of radioactive changes, especially where energy relations are involved. The heat evolved by radium is in the main accounted for by the energy of the particles and of the recoil atoms. When the quantity of heat is calciJlated it is found that all of it is not accounted for, provided use is made of the experimentally determined rate of emission of particles. This investigation is undertaken with the intent of securing an entirely reliable determination of this rate. It is found that one gram of radium in one second emits 3.68 X IO~° alpha particles. Geiger and Werner recently publish as their result 3.4o X IOn°while Rutherford and Geiger obtained 3.57 X IO~°. When the new result is used for the calculation of the heat developed excellent agreement is seen between the calculated and the experimentally obtained quantities of heat. G.F.S. Visible Radiation Characteristics of Incandescent Oxides. MARCELLA L. PHILLIPS. (Physical Review, Nov., 1928.) A study was made of the visible radiation characteristics of urania, ceria, lanthana, neodymia, erbia, yttria, zirconia, thoria, alumina, beryllla, magnesia and of certain mixtures. These were heated to red brightness temperatures ranging from 1,4oo to 2,000 ° K. and the total emission at each temperature in candles per sq. cm. and the blue brightness in terms of the blue brightness of the black body at the temperature of melting palladium are tabulated. At the lowest observed temperature of 1,4oo ° K. a black body has a blue brightness of .oo61. The following substances have values of this quantity lying between .006 and .oi, vlz., tungsten, urania, ceria neodymia, lanthana, zirconia, thoria, and beryllia. At the temperature considered magnesia has the greatest blue brightness, .o71. Magnesia has also the greatest emission per sq. cm., vlz., about one candle per sq. cm. This becomes 79 at 2,000 ° K., but at that temperature it is exceeded by alumina and beryllia. Elevating the temperature from 1,4oo ° to 2,0o0 ° K. produces the largest relative increase in radiation per sq.cm, in the case of yellow ceria where the emissions at the respective temperatures are .36 and 88.0. For a black body the values for the two temperatures are .26 and 44.0. G . F . S .
CURRENT TOPICS.
]J. F. I.
The Rate of Emission of Alpha Particles from Radium. (Proc. Roy. Soc., A 787.) H . J . J . BRADDICKand H. M. CAve,:. The number of alpha particles emitted by a unit mass of radium in unit time is quite an important constant in the interpretation of radioactive changes, especially where energy relations are involved. The heat evolved by radium is in the main accounted for by the energy of the particles and of the recoil atoms. When the quantity of heat is calciJlated it is found that all of it is not accounted for, provided use is made of the experimentally determined rate of emission of particles. This investigation is undertaken with the intent of securing an entirely reliable determination of this rate. It is found that one gram of radium in one second emits 3.68 X IO~° alpha particles. Geiger and Werner recently publish as their result 3.4o X IOn°while Rutherford and Geiger obtained 3.57 X IO~°. When the new result is used for the calculation of the heat developed excellent agreement is seen between the calculated and the experimentally obtained quantities of heat. G.F.S. Visible Radiation Characteristics of Incandescent Oxides. MARCELLA L. PHILLIPS. (Physical Review, Nov., 1928.) A study was made of the visible radiation characteristics of urania, ceria, lanthana, neodymia, erbia, yttria, zirconia, thoria, alumina, beryllla, magnesia and of certain mixtures. These were heated to red brightness temperatures ranging from 1,4oo to 2,000 ° K. and the total emission at each temperature in candles per sq. cm. and the blue brightness in terms of the blue brightness of the black body at the temperature of melting palladium are tabulated. At the lowest observed temperature of 1,4oo ° K. a black body has a blue brightness of .oo61. The following substances have values of this quantity lying between .006 and .oi, vlz., tungsten, urania, ceria neodymia, lanthana, zirconia, thoria, and beryllia. At the temperature considered magnesia has the greatest blue brightness, .o71. Magnesia has also the greatest emission per sq. cm., vlz., about one candle per sq. cm. This becomes 79 at 2,000 ° K., but at that temperature it is exceeded by alumina and beryllia. Elevating the temperature from 1,4oo ° to 2,0o0 ° K. produces the largest relative increase in radiation per sq.cm, in the case of yellow ceria where the emissions at the respective temperatures are .36 and 88.0. For a black body the values for the two temperatures are .26 and 44.0. G . F . S .