Uranium Group

This element is usually classed with Fe and Or, or with Ni and Co. It does not, however, form compounds resembling the ferric it forms a series of well-defined uranates, and a series of compounds of the radical uranyl (UO). Standard solutions of its acetate or nitrate are used for the quantitative determination of HjPO.  

Symbol = Dh (PLUMBUM)—Atomic weight = 206.9—Molecular weight =413.8 t)—Sp. gr.= 11.445—FWej at 325° (617° F.)—Name from Imd = heavy (Saxon). 

Lead is usually classed with Cd, Bi, or Cu and Hg. It differs, however, from Bi in being bivalent or quadrivalent, but not trivalent, and in forming no compounds, resembling those of bismuthyl (BiO) from Cd, in the nature of its O compounds and from Cu and Hg in fonning no compounds similar to the mercurous and cuprous salts. Indeed, the nature of the Pb compounds is such that the element is best classed in a group by itself, which finds a place in this class by virtue of the existence of potassium plumbate. 

Occurrence.—Its most abundant ore is galena, PbS. It also occurs in white lead ore, PbCO , in anglesite, PbSO , and in horn lead, PbCli. 

Preparation.—Galena is first roasted with a little lime. The mixture of PbO, PbS, and PbSOi, so obtained, is strongly heated in a reverberatory furnace, when SOa is driven off. The impure work lead, so formed, is purified by fusion in air, and removal of the film of oxids of Sn and Sb. If the ore be rich in Ag, that metal is extracted, by taking advantage of the greater fusibility of an alloy of Pb and Ag, than of Pb alone and subsequent-oxidation of the remaining Pb. 

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Nuphar lutea, a plant very sensitive to perturbations such as those which may accompany the mining of metal ores, was also examined in order to measure the content of radionuclides in a series of uranium group elements (11). In experiments carried out in the Okanagan region of south-central British Columbia, N. lutea was found to accumulate natural uranium and 226 Ra, and the amounts of these elements were found to depend on the season and also on the pH of the mud. Nuphar lutea was also used in investigations into the concentration of137Cs and potassium in Lake Ulkesjon in the southern part of Sweden (12). 

Uranium, neptunium, and plutonium were considered to be sort of "cousins in the Periodic Table as it was understood in 1944, but the family relationship was not clear. It was thought that elements 95 and 96 should be much like them in their chemical properties. Thus it was thought that these elements formed a "uranide ( like uranium ) group. 

Uranium group Uranium orange Uranium yellow Allpress (1964) Klima et al. (1966)... 

Uranium group Uranium oxides and hydroxides group Pitchblende... 

Uranium group Barium uranium oxide Salter (1869) 260-261... 

Uranium group Barium uranium oxide Ochre Pitchblende Uraninite Uranium yellow... 

Reaction of tris-cyclopentadienyluranium(iv) chloride with two moles of Li(CH2)2PPha at — 50 °C affords the first actinide phospho-ylide complex. The new compound forms red, air- and moisture-sensitive crystals whose structure (1) has been determined from an JT-ray study. Two bis(cyclopentadienyl)uranium groups are essentially bridged by the ylide ligand, which is unique in that it also... 

Diaconescu PL, Odom AL, Agapie T, Cummins CC (2001) Uranium-group 14 element single bonds isolation and characterization of a uranium(IV) silyl species. Organometallics 20 4993... 

The larger cations of Group 1 (K, Rb, Cs) can be precipitated from aqueous solution as white solids by addition of the reagent sodium tetraphenylborate, NaB(C( H5)4. Sodium can be precipitated as the yellow sodium zinc uranium oxide ethanoate (sodium zinc uranyl acetate). NaZn(U02)3(CH3C00)y. 9H2O. by adding a clear solution of zinc uranyl acetate in dilute ethanoic acid to a solution of a sodium salt. 

The actinide elements are a group of chemically similar elements with atomic numbers 89 through 103 and their names, symbols, atomic numbers, and discoverers are given in Table 1 (1-3) (see Thorium and thorium compounds Uranium and uranium compounds Plutonium and plutonium compounds Nuclear reactors and Radioisotopes). 

Thorium, uranium, and plutonium are well known for their role as the basic fuels (or sources of fuel) for the release of nuclear energy (5). The importance of the remainder of the actinide group Hes at present, for the most part, in the realm of pure research, but a number of practical appHcations are also known (6). The actinides present a storage-life problem in nuclear waste disposal and consideration is being given to separation methods for their recovery prior to disposal (see Waste treati nt, hazardous waste Nuclear reactors, waste managet nt). 

Lead, atomic number 82, is a member of Group 14 (IVA) of the Periodic Table. Ordinary lead is bluish grey and is a mixture of isotopes of mass number 204 (15%), 206 (23.6%), 207 (22.6%), and 208 (52.3%). The average atomic weight of lead from different origins may vary as much as 0.04 units. The stable isotopes are products of decay of three naturally radioactive elements (see Radioactivity, natural) comes from the uranium series (see Uraniumand... 

Meta.soina.tlte Deposits. Included in the metasomatite deposit grouping are uranium deposits in alkah metasomatites, eg, albitites, aegirinites, and alkah—amphibole rocks, commonly intmded by microcline granite. Examples are the deposits in Espinharasin, Brazil, and Ross Adams, Alaska, as well as the Zheltye Vody deposit in Krivoy Rog area in Ukraine (16). 

Group 3 (IIIB) and Inner Transition-Metal Perchlorates. The rare-earth metal perchlorates of yttrium and lanthanum have been reported (53). Tetravalent cerium perchlorate [14338-93-3] 06(0.04)4, and uranium perchlorate have also been identified (54). 

The O or S atoms in P=0 and P=S groups may act as electron donors although these groups form relatively weak complexes with electron acceptor compounds such as nonpolarizable, more electropositive (ie, hard) acids, including protons (14). Use is made of this property in the recovery of uranium from wet-process phosphoric acid by extractants such as trioctylphosphine oxide [78-50-2] and di(2-ethylhexyl) hydrogen phosphate [298-07-7]. 

Catalysts used for preparing amines from alcohols iaclude cobalt promoted with tirconium, lanthanum, cerium, or uranium (52) the metals and oxides of nickel, cobalt, and/or copper (53,54,56,60,61) metal oxides of antimony, tin, and manganese on alumina support (55) copper, nickel, and a metal belonging to the platinum group 8—10 (57) copper formate (58) nickel promoted with chromium and/or iron on alumina support (53,59) and cobalt, copper, and either iron, 2iac, or zirconium (62). 

Aromatic amines form addition compounds and complexes with many inorganic substances, such as ziac chloride, copper chloride, uranium tetrachloride, or boron trifluoride. Various metals react with the amino group to form metal anilides and hydrochloric, sulfuric, or phosphoric acid salts of aniline are important intermediates in the dye industry. 

A number of special processes have been developed for difficult separations, such as the separation of the stable isotopes of uranium and those of other elements (see Nuclear reactors Uraniumand uranium compounds). Two of these processes, gaseous diffusion and gas centrifugation, are used by several nations on a multibillion doUar scale to separate partially the uranium isotopes and to produce a much more valuable fuel for nuclear power reactors. Because separation in these special processes depends upon the different rates of diffusion of the components, the processes are often referred to collectively as diffusion separation methods. There is also a thermal diffusion process used on a modest scale for the separation of heflum-group gases (qv) and on a laboratory scale for the separation of various other materials. Thermal diffusion is not discussed herein. 

Compounds with Sc, Y, lanthanoids and actinoids are of three types. Those with composition ME have the (6-coordinated) NaCl structure, whereas M3E4 (and sometimes M4E3) adopt the body-centred thorium phosphide structure (Th3P4) with 8-coordinated M, and ME2 are like ThAsi in which each Th has 9 As neighbours. Most of these compounds are metallic and those of uranium are magnetically ordered. Full details of the structures and properties of the several hundred other transition metal-Group 15 element compounds fall outside the scope of this treatment, but three particularly important structure types should be mentioned because of their widespread occurrence and relation to other structure types, namely C0AS3,... 

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