The Search for Element No. 87

An attempt to secure the element 87 $L{\alpha }_{1,2}$ x-ray lines in fluorescence spectra is made with negative results: no trace of the line sought for was found. The fluorescent material was CsHS${\mathrm{O}}_4$ derived from lepidolite, in which free thallium has been found. The writer suggests that the free thallium is derived from unstable element 87 atoms which had been present in the lepidolite molecule.