Rubidium, caesium, thallium, indium and gallium were first discovered by means of this instrument; the study of the rare earths is greatly facilitated, and the composition of the heavenly bodies alone determinable by it.
ERBIUM (symbol, Er; atomic weight, 165-166), one of the metals of the rare earths.
In 1883 he began an inquiry into the nature and constitution of the rare earths.
After removing the uranium, it was found that the bismuth separated with a very active substance - polonium; this element was afterwards isolated by Marckwald, and proved to be identical with his radiotellurium; that the barium could be separated with another active substance - radium; whilst a third fraction, composed mainly of the rare earths (thorium, &c.), yielded to Debierne another radioactive element - actinium, which proved to be identical with the emanium of Giesel.
LANTHANUM [[[symbol]] La, atomic weight 139.0 (0=16)] one of the metals of the cerium group of rare earths.