Mosanders Discoveries Checked. Were They Correct

Mosander s Discoveries Checked. Were They Correct  

The 35 years after 1840 were uneventful regarding the discovery of rare earth elements. Berzelius had died in 1848, Mosander in 1858. Inorganic chemistry was under pressure from the growing organic chemistry. The introduction of a new analytical technique, spectroscopy, however, aroused new interest and opened new approaches. The gradual separation of one element from another could be followed. This was very valuable in the many and time-consuming fractional crystallizations. 

There seemed to be no doubt about the existence of lanthanum and didymium. Around 1850, Marignac in Switzerland determined their atomic weights and carefully investigated the chemistry of the two elements. 

Bunsen s investigation seemed to show that terbium does not exist But the argument is dubious. Spectroscopy was in its infancy and the method was very empirical. 

The wavelengths in the spectrum of an element X were recorded by investigating a sample of pure X. To find out if an unknown sample contained element X, the sample s spectrum was examined for lines from element X. If Bunsen had never seen the element terbium he could know nothing about its spectrum. Bunsen and Bahr s investigations had little value as evidence in the terbium debate. 

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