CERIUM AND THORIUM OXIDES. 



IJ 3 



high, corresponding closely to that of a complete radiator, as was shown 

 by Rubens, using a gas-mantle of this material. 



The cerium-oxide curve shows a strong emission at 2 to 3 /*, as was 

 found by Rubens, with possible bands at 4.4 and 7.5 p.. It was shown by 

 Rubens that beyond 7 // the emissivity approaches that of a complete 

 radiator. 



0/234 5. 6 7 8 9/1 



Fig. 80. Nernst glower (a); Nernst "heater-tube" (6); Magnesium oxide. 



In the Auer gas mantle (90 per cent Th0 2 + 1 per cent Ce0 2 ) the cerium 

 oxide acts as a sensitizer does on a photographic plate, by making an ab- 

 sorption band in one region of the spectrum without affecting the rest. 



The energy curve of an electrically heated filament of the same com- 

 position as the Auer mantle is given in the Bulletin of the Bureau of 

 Standards, vol. 5, No. 2, 1908. The energy curve is entirely different 



