Didymium discovery

Nor was Mendeleev s revolutionary Periodic Table a help. When he first published his Periodic Table in 1869, he was able to include only lanthanum, cerium, didymium (now known to have been a mixture of Pr and Nd), another mixture in the form of erbia, and yttrium unreliable information about atomic mass made correct positioning of these elements in the table difficult. Some had not yet been isolated as elements. There was no way of predicting how many of these elements there would be until Henry Moseley (1887-1915) analysed the X-ray spectra of elements and gave meaning to the concept of atomic number. He showed that there were 15 elements from lanthanum to lutetium (which had only been identified in 1907). The discovery of radioactive promethium had to wait until after World War 2. 

Cerite was thoroughly studied by Swedish chemist Carl Gustav Mosander (1797-1858). In 1839, Mosander was able to separate cerite into two parts, which he called cerium and lanthanum. Mosander believed he had found two new elements. Two years later, however, he learned that his lanthanum was not an element but a mixture of two parts. Mosander called these two new parts lanthanum and didymium. Mosander chose the name didymium because it means twin. He said that didymium was like an identical twin to lanthanum. Chemists later confirmed that two of Mosander s discoveries were really new elements cerium and lanthanum. 

The discovery of samarium grew out of this kind of frustration. In 1880, French chemist Paul-emile Lecoq de Boisbaudran (1838—1912) was studying a substance known as didymium. Earlier chemists believed didymium might be a new element. Boisbaudran said that at least two new elements were present in didymium. 

The discovery of the rare earths in 1794 was a prototype of a surprise, it was not just one more metallic element, such as strontium and titanium. Many early observations are fascinating Berzelius report that a very high concentration of didymium can be kept in solution in aqueous ammonia containing ammonium... 

Yttrium asserted its individuality later. Whether Mosander obtained pure terbium or not remains unclear. Erbium had the same fate as didymium. And one more correction in the list of official discovery dates is necessary real yttrium was extracted by Mosander in 1843. Therefore, it is Mosander who stood at the cradle of REEs. 

In his opinion, a new previously unknown element contained in didymium was responsible for the appearance of the new lines in the spectrum. He named it decipium from the Latin to deceive, to stupefy and the name proved to be ironical decipium turned out to be a mixture of several REEs both known and unknown ones. Decipium was debunked in 1879 by L. de Boisbaudran of France who played a prominent role in the discovery of new REEs. In the next chapter we shall tell you how he discovered gallium predicted by Mendeleev. Boisbaudran extracted didymium from samarskite and thoroughly studied the sample by spectroscopy. Boisbaudran was a much more skillful experimenter than Delafontaine and he succeeded in separating the impurity from didymium . He named the new element samarium after samarskite, being unaware that samarium was also a mixture of elements. Boisbaudran s discovery was immediately confirmed by Marignac who, after multiple recrystallizations of samarium , separated two fractions which he marked Y and Yp (not to be confused with the symbol of yttrium Y ). The spectrum of the second fraction was identical to the spectrum of samarium . As to the first fraction, we shall have a look at it a little later. 

Discovery Carl Gustaf Mosander in Stockholm discovered didymium, the twin , in 1840. Carl Auer von Welsbach in Vienna discovered in 1885 that didymium is composed of two elements. One of them he called praseodymium the green twin , the other neodymium the new twin . 

Discovery Paul-Emile Lecoq de Boisbaudran in Paris discovered a new element in didymium in 1879. He gave it the name samarium after the mineral samarskite. 

From Figure 17.3 it is clear that the history of discoveries falls into three different periods. The first, about 1800, was the time for the basic discoveries, yttrium and cerium the second, around 1840, resulted in four new elements, erbium, terbium, lanthanum and didymium. Not until the introduction of the spectroscopy in the middle of the 19 century and the development of improved separation techniques did the discoveries enter the third period, 1870-1910. Yet, the last REM, promethium, was not discovered until 1945. Some biographical information about the actual discoverers is given along with the different discovery descriptions below. 

This laboratory, described with such great insight by Johnston, certainly influenced the development of laboratories and examination techniques in other parts of Europe. The fact that the famous German chemist Friedrich Wohler frequently worked as a visiting scientist in the laboratory also contributed to its influence. Carl Gustaf Mosander s substantial work with rare earths around 1840 was also performed here. This led to the discovery of the elements lanthanum, didymium, erbium and terbium. 

In 1878 Delafontaine made an important observation. He isolated didymium both from cerite and from the mineral samarskite . Absorption spectra obtained during examination of the two didymium samples were different. To Delafontaine this was an indication that didymium was not a homogenous element This interested Bois-baudran in France. Unlike Delafontaine he used emission and not absorption spectroscopy. He found Hnes showing the presence of a previously unknown element In 1879 he announced the discovery with the information that its name was samarium after the mineral. 

Mosander s didymium was banished to a backyard of chemistry, which depreciates his enormous contribution to element discovery. Instead Auer is credited with both the twin elements associated with his name, as shown in Table 17.8... 

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