Praseodymium Element

Naturally occurring praseodymium (Pr) has only one stable isotope, Pr. Thirty-eight radioisotopes are known, of which Pr is the most stable with a half-life of 13.57 days and Pr with a half-life of 19.12 h. All other isotopes have half-lives shorter than 6 h and for many shorter than 33 s. 

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Zirconium oxide is used in the production of ceramic colors or stains for ceramic tile and sanitary wares. Zirconia and siHca are fired together to form zircon in the presence of small amounts of other elements which are trapped in the zircon lattice to form colors such as tin—vanadium yellow, praseodymium—zircon yellow [68187-15-5] vanadium—zircon blue [12067-91 -3] iron—zircon pink [68412-79-3] indium—vanadium orange (105—108). 

Accurate atomic weight values do not automatically follow from precise measurements of relative atomic masses, however, since the relative abundance of the various isotopes must also be determined. That this can be a limiting factor is readily seen from Table 1.3 the value for praseodymium (which has only 1 stable naturally occurring isotope) has two more significant figures than the value for the neighbouring element cerium which has 4 such isotopes. In the twelve years since the first edition of this book was published the atomic weight values of no fewer than 55 elements have been improved, sometimes spectacularly, e.g. Ni from 58.69( 1) to 58.6934(2). 

Figure 16 shows the charge-discharge cycle characteristics of alloys in which part of the nickel component was replaced with cobalt. Misch metal (Mm), which is a mixture of rare earth elements such as lanthanum, cerium, praseodymium, and neodymium, was used in place of lanthanum. It was found that the partial replacement of nickel with cobalt and the substi-... 

Praseodymium tri-iodide, Prl3, as the starting material for reduction reactions, might be easily produced by the oxidation of praseodymium metal with elemental iodine [17]. With catalytic amounts of hydrogen dissolved in praseodymium metal powder, the reaction temperature can be as low as 230 °C [18]. Sublimation in high vacuum in tantalum tubes yields pure Prl3. 

Tin hold the record with 10 stable isotopes. There are 19 so-called "pure elements" of which there is only one isotope. These anisotopic elements are beryllium, fluorine, sodium, aluminum, phosphorus, scandium, manganese, cobalt, arsenic, yttrium, niobium, rhodium, iodine, cesium, praseodymium, terbium, holmium, thulium, gold, and bismuth. 

Some of the 105 elements now known to exist are very familiar to everyone because they are commonplace in our daily lives. Typical examples are iron, tin, and lead. Others, such as lanthanum, holmium, and praseodymium will probably be new to you. How many of the 105 elements can you actually name Gold Silver Copper Did you think of hydrogen and oxygen ... 

These include the following 14 elements cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmi-um, erbium, thulium, ytterbium, and lutetium. 

The variation in enthalpies of solution of the hexahydrates parallels approximately that for the values for the anhydrous compounds (Fig. 1). It is interesting that the difference between the enthalpies of solution of the hexa- and heptahydrates of praseodymium trichloride is approximately 14 kJ mol-1, which compares closely with a mean value of 13 kJ mol-1 per water molecule for salts of sp- and of d-block elements (203). The differences between the enthalpies of solution of the hexahydrates and of the respective anhydrous trichlorides correspond to 20-25 kJ mol-1 per water molecule. 

A kind of summary of the similarities which, albeit with some uncertainties, may be evidenced between the single lanthanide and actinide metals is reported, according to Ferro et al. (2001a) in Fig. 5.13. According to this scheme the alloying behaviour of plutonium could be simulated by cerium whereas a set of similarities may especially be considered between the block of elements from praseodymium to samarium with those from americium to californium. 

In conclusion I should like to consider a few of the chemical investigations which might be accomplished in the rare earth field by Mossbauer spectroscopy. The study of nonstoichiometric oxides has been discussed earlier, but there is the problem of finding an appropriate doping nuclide for the praseodymium oxide system. The element most capable of following the changes in oxidation state of the praseodymium is terbium-159, which does have a Mossbauer state, however, with a rather broad resonance (58,0 k.e.v., = 0.13 nsec.). Nevertheless, with a sufiiciently... 

Praseodymium - the atomic number is 59 and the chemical symbol is Pr. The name was originally praseodidymium and was later shortened to praseodymium, which is derived from the Greek prasios for green and didymos for twin because of the pale green salts it forms. It was discovered by the Austrian chemist Carl Auer von Welsbach in 1885, who separated it and the element neodymium from a didymium sample. Didymium had previously been thought to be a separate element. 

Praseodymium is the 41st most abundant element on Earth and is found in the ores of mona-zite, cerite, bastnasite, and allanite along with other rare-earths. Praseodymium is also the stable isotope resulting from the process of fission of some other heavy elements, such as uranium. 

At first praseodymium was called didymium, which is Greek for twin, because it was always found with another rare-earth element. Using spectroscopic analysis, the two different color bands, one green and one yellow, indicated that there were two elements in didymium, but no one could identify the new elements. 

In 1885 Carl Auer Baron von Welsbach (1858-1929) separated the oxides of two similar elements from didymium. He named one praseodymium from the Greek word prasios, which means green or the green twin, and he named the other element neodymium, which is derived from new and dymium and means new twin. ... 

Using a spectrometer in 1853, Jean Charles-GaUisard de Marignac (1817—1894) suspected that dydimia was a mixture of yet-to-be-discovered elements. However, it was not until 1879 that Paul-Emile Locoq de Boisbaudran (1838—1912), using a difficult chemical fractionation process, discovered samarium in a sample of samarskite, calling it samarium after the mineral, which was named for a Russian mine official. Colonel von Samarski. Samarskite ore is found where didymia is found. Didymia ( twins ) was the original name given to a combination of the two rare-earths (praseodymium and neodymium) before they were separated and identified. 

Mosander extracted from the mineral lanthana a rare earth fraction, named didymia in 1841. In 1879, Boisbaudran separated a rare earth oxide called samaria (samarium oxide) from the didymia fraction obtained from the mineral samarskite. Soon after that in 1885, Baron Auer von Welsbach isolated two other rare earths from didymia. He named them as praseodymia (green twin) and neodymia (new twin) after their source didymia (twin). The name praseodymium finally was assigned to this new element, derived from the two Greek words, prasios meaning green and didymos meaning twin. 

Important is the use of light rare earth elonents for production of hard magnetic materials. Most prominent are alloys of samarium with cobalt in the atomic ratio 1 5 or 2 17. It may also be assumed that in further development of these materials on a larger scale that praseodymium, neodymium, lanthanum and also individual heavy rare ecu h elements will be used to achieve particular effects. Interesting is the development of magnetic bubble memories based on gadolinium-galliiimrgarnets. 

As a final introductory point, it should be noted that there is some confusion within the foundry industry, and its literature, regarding the specific rare earths being employed. Early work in this field was conducted using mischmetal. However, in many instances, only the cerium level was reported in these tests. The presence of the other rare earths was ignored. Even today, the elements most often mentioned are the first four lanthanides lanthanum, cerium, praseodymium and neodymium. That is not to say that the effects of the other elements in the series would not be similar to those of the first four or that they could not be utilized. Rather, their roles have not been studied individually. 

These same researchers also explored the efficacy of the individual rare earths as nodulizers (17). They concluded, by their ability to produce nodular iron having adequate physical properties without excessive iron carbides present, that cerium was the most effective of the four rare earth elements (lanthanum-neodymium) evaluated as nodulizers. They reported that it required 1.5 times as much neodymiun or praseodymium and three times as much lanthanum as cerium to yield equivalent results. 

Similar deleterious effects of small concentrations (that is, 0.001% to 0.005%) have been well documented for bismuth and antimony. Similarly, these effects were overcome by additions of small amounts of the rare earth elements. In the industry, it is accepted that roughly 0.01% cerium (once again as mischmetal that contains 50% cerium and approximately 50% lanthanum, neodymium and praseodymium) will neutralize the effects of the deleterious elements. The result is the production of high quality nodular iron, while still allowing for the use of commercially available steel scrap as a raw material. 

The lanthanide metals should also be investigated to higher pressures than previously applied. It is not excluded that their 4 f electrons also participate in bonding as do the 5 f s of Bk and Cf, after the dhcp, ccp and, possibly, distorted fee phases have been reached. An indication of this possibility can be seen in the recent discovery of the a-uranium structure type in praseodymium (Pr IV) . This structure type was previously observed for cerium, but was thought to be restricted to that metal which has an exceptional position among the lanthanide elements. 

After the brilliant researches of Bunsen and Kirchhoff had paved the way, other new elements were soon revealed by the spectroscope. Among these may be mentioned thallium, indium, gallium, helium, ytterbium, holmium, thulium, samarium, neodymium, praseodymium, and lutetium. 

The final answer came from the atomic pile. J. A. Marinsky, L. E. Glendenin, and C. D. Coryell at the Clinton Laboratories at Oak Ridge (20) obtained a mixture of fission products of uranium which contained isotopes of yttrium and the entire group of rare earths from lanthanum through europium. Using a method of ion-exchange on Amberlite resin worked out by E. R. Tompkins, J. X. Khym, and W. E. Cohn (21) they were able to obtain a mixture of praseodymium, neodymium, and element 61, and to separate the latter by fractional elution from the Amberlite column with 5 per cent ammonium citrate at pH 2.75. Neutron irradiation of neodymium also produced 61. 

Geneva found a further earth in this substance, which Lecoq isolated in 1886 and called gadolinium. Didymium itself, meanwhile, was revealed as a phantom, a mixture of two new elements that Karl Auer in Austria discovered in 1885 and called neodymium ( new didymium ) and praseodymium ( green didymium ). Just how many of these earth elements were there, after all ... 

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