Discovery of a new element ‘nipponium’: re-evaluation of pioneering works of Masataka Ogawa and his son Eijiro Ogawa

Masataka Ogawaʹs discovery of nipponium was accepted once in the periodic table of chemical elements as the element 43, but disappeared later. However, nipponium clearly shows characteristics of rhenium (Z=75) by inspection of his papers from the modern chemical viewpoints. The present author tried to get more evidences by some experimental approaches including X-ray spectroscopy. The most important finding was that a record of X-ray spectrum of Ogawaʹs nipponium sample from thorianite was contained in a photographic plate reserved by his family. The spectrum was read and indicated the absence of the element 43 and the presence of the element 75 (rhenium). Nipponium works by Masataka and Eijiro Ogawa have been re-evaluated.