Carl Auer, later and in consequence
known as Baron Auer von Welsbach. He was trying to sort out the rare
earths by means of the spectroscopic method, which consists ordinarily
in dipping a platinum wire into a solution of the unknown substance and
holding it in a colorless gas flame. As it burns off, each element gives
a characteristic color to the flame, which is seen as a series of lines
when looked at through the spectroscope. But the flash of the flame from
the platinum wire was too brief to be studied, so Dr. Auer hit upon the
plan of soaking a thread in the liquid and putting this in the gas jet.
The cotton of course burned off at once, but the earths held together
and when heated gave off a brilliant white light, very much like the
calcium or limelight which is produced by heating a stick of quicklime
in the oxy-hydrogen flame. But these rare earths do not require any such
intense heat as that, for they will glow in an ordinary gas jet.
So the Welsbach mantle burner came into use everywhere and rescued the
coal gas business from the destruction threatened by the electric light.
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