Greater or less proportions of ceria decreased the light-output.
It is the ceria that gives the light, yet a little more of it will lower the luminosity.
In this way a very high initial illuminating power was obtained, which, however, rapidly fell as the ceria slowly volatilized.
The oxyacetylene flame is concentrated upon a small pellet of ceria, which provides a brilliant source of small dimensions.
These crude earths, yttria and ceria, have supplied most if not all of the “rare earth” metals.