Delafontaine, Marc

Dehydrogenation reactions, 357 Delafontaine, Marc, 8 Demargay, Eugene-Anatole, 8 Demonium, 7 Density of state (DOS), 140 Dextran T-10,308... 

Per Theodor Cleve (1840-1905) independently Marc Delafontaine (1837-1911) and J.-L. Soret (1827-1890). 

Dysprosium - the atomic number is 66 and the chemical symbol is Dy. The name derives from the Greek dysprositos for hard to get at , due to the difficulty in separating this rare earth element from a holmium mineral in which it was found. Discovery was first claimed by the Swiss chemist Marc Delafontaine in the mineral samarskite in 1878 and he called it philippia. Philippia was subsequently found to be a mixture of terbium and erbium. Dysprosium was later discovered in a holmium sample by the French chemist Paul-Emile Lecoq de Boisbaudron in 1886, who was then credited with the discovery. It was first isolated by the French chemist George Urbain in 1906. 

Samarium - the atomic number is 62 and the chemical symbol is Sm. The name derives from the mineral Samarskite, in which it was found and which had been named for Colonel von Samarski , a Russian mine official. It was originally discovered in 1878 by the Swiss chemist Marc Delafontaine, who called it decipium. It was also discovered by the French chemist Paul-Emile Lecoq de Boisbaudran in 1879. In 1881, Delafontaine determined that his decipium could be resolved into two elements, one of which was identical to Boisbaudran s samarium. In 1901, the French chemist Eugene-Anatole Demar9ay showed that this samarium earth also contained europium. 

Terbium - the atomic number is 65 and the chemical symbol is Tb. The name derives from the village of Ytterby in Sweden, where the mineral ytterbite (the source of terbium) was first found. It was discovered by the Swedish surgeon and chemist Carl-Gustav Mosander in 1843 in an yttrium salt, which he resolved into three elements. He called one yttrium, a rose colored salt he called terbium and a deep yellow peroxide he called erbium. The chemist Berlin detected only two earths in yttrium, i.e., yttrium and the rose colored oxide he called erbium. In 1862, the Swiss chemist Marc Delafontaine reexamined yttrium and found the yellow peroxide. Since the name erbium had now been assigned to the rose colored oxide, he initially called the element mosandrum (after Mosander) but he later reintroduced the name terbium for the yellow peroxide. Thus the original names given to erbium and terbium samples are now switched. Since Bunsen spectroscopically examined Mosander s erbium (now terbium) sample and declared that it was a mixture, the question of who actually discovered terbium, Mosander or Delafontaine remains unresolved to this day. 

In the 1800s chemists searched for new elements by fractionating the oxides of rare-earths. Carl Gustaf Mosander s experiments indicated that pure ceria ores were actually contaminated with oxides of lanthanum, a new element. Mosander also fractionated the oxides of yttria into two new elements, erbium and terbium. In 1878 J. Louis Soret (1827—1890) and Marc Delafontaine (1837-1911), through spectroscopic analysis, found evidence of the element holmium, but it was contaminated by the rare-earth dysprosia. Since they could not isolate it and were unable to separate holmium as a pure rare-earth, they did not receive credit for its discovery. 

Mosande/s work was confirmed by Marc Delafontaine, J.-C. G. de Marignac, J. Lawrence Smith, P. T. Cleve, and Lecoq de Boisbaudran, but, for some reason, a confusing shift of names occurred. The names erbia and terbia were interchanged, so that the former now applies to... 

Marignac believed as early as 1853 that Mosander s didymia was not a pure substance, and later spectroscopic work of Marc Delafontaine and of Lecoq de Boisbaudran indicated that the spectrum of didymia varied according to its source. Boisbaudran in 1879 added ammonium hydroxide to a solution of it, and noticed that another earth precipitated before the didymia. Since the spectrum of this new oxide was found to be different... 

Marc Delafontaine (1837-1911) was born in Switzerland. He probably studied at the University of Geneva and worked there for some time. Later he emigrated to the United States and continued his activities in chemistry and geology there. I was unable to find any further biographical facts concerning Delafontaine. 

Swiss scientists Jacques-Louis Soret and Marc Delafontaine discover the element holmium, which also is independently discovered by Swedish chemist Per Theodor Cleve. Swiss chemist Jean-Charles de Marignac discovers the element ytterbium. 

Holmium 1878 Marc Delafontaine (Switzerland) and Jacques (Switzerland) Per Theodor Cleve (Sweden) -Louis Soret... 

Per T. Cleve, Uppsala Marc Delafontaine, Geneva Louis Soret, Geneva Holmium 1878 Spectroscopy was invented about 1850. It was of great benefit in REM discoveries... 

Two other Swiss, also from Geneva, had considerable achievements in the discovery of rare earth elements. They were Louis Soret (1827-1890) and Marc Delafontaine (1837-1911). The former was professor of physics at the univer-... 

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