Promethium oxide

In addition to their intrinsic theoretical interest and as models for other systems, the oxides of the rare earths have many practical uses. They are receiving attention in industry because of their potential use as control rods for nuclear reactors where samarium, gadolinium and europium oxides are incorporated into cermets or are used in fuel elements as burnable poisons. Radioactive europium and thulium oxides are used as heat sources and promethium oxide as a jS source. Lanthanide oxide catalysts may be... 

The main oxidation state for promethium is +3. At least 30 compounds of promethium have been identified, but none are commercially available. Three examples of typical rare-earth metal compounds are as follows ... 

In solution, neptunium oxidizes to Np + and Np + ions, the salts of which are pink and greenish-yellow, respectively. Unlike its rare earth analog promethium, neptunium also forms oxoions, such as, NpO" " (blue green) and NpQ2+ (light pink). 

Tracer studies of the chemical properties showed that astatine was soluble in organic solvents, could be reduced to the —1 state, and had at least two positive oxidation states. These studies were made on solutions of 10-11 to KL15 molar astatine (29). The similarity between astatine and iodine was found to be less close than that between technetium and rhenium or that between promethium and the other rare earths (30). 

C.A. Arrhenius, in 1787, noted an unusual black mineral in a quarry near Ytterby. Sweden, This was identified later as containing yttrium and rare-earth oxides. With the exception of promethium, all members of the Lanthanide Series had been discovered by 1907, when lutetium was isolated. In 1947. scientists at the Atomic Energy Commission at Oak Ridge National Laboratory (Tennessee) produced atomic number 61 from uranium fission products and named it promethium. No stable isotopes of promethium have been found in the earth s crust. 

The lighter metals (La—Gd) are obtained by reduction of the trichlorides with Ca at 1000°C or more, whereas for others (Tb, Dy, Ho, Er, Tm, and also Y) the trifluorides are used because the chlorides are too volatile. Promethium metal is made by reduction of PmF3 with Li. Trichlorides of Eu, Sm, and Yb are reduced only to the dihalides by Ca, but the metals can be prepared by reduction of the oxides M203 with La at high temperatures. 

PmCl3.xH20, Pm(N03)3.xH20, and Pm(C2O4)3.10H2O. It would be expected that promethium would form some stable compounds in the +2 oxidation state, though they are unlikely to be made in aqueous solution. No definite evidence has yet been obtained, since studies have been hindered both by the small quantities of the element available and by its radioactivity. The properties of promethium fit neatly into position between neodymium and samarium it is a microcosm of lanthanide chemistry in general. 

Relatively little is known about the chemistry of promethium, although the established facts highlight the resemblance of promethium to the lanthanides that flank it. The halides are well defined, and have been shown to have the expected structures (Table 2). Thus in a recent study, starting with some 100 J,g of Pm203, the halides were synthesized microchemically, using the reaction with fluorine for PmFs and the reaction with HX (X = Cl, Br) for the chloride and bromide the latter two reacted with HI to give the iodide. Pm203 is one of the few lanthanide oxides to crystallize in three modifications. 

It would be expected that promethium would form some stable compounds in the -1-2 oxidation state, but no definite evidence has yet been obtained since studies have been hindered both by the small quantities available and by its radioactivity. 

Sullivan MF, Ruemmler PS, Ryan JL, et al. 1986. Influence of oxidizing or reducing agents on gastrointestinal absorption of uranium, plutonium, americium, curium, and promethium by rats. Health Phys 50 233-232. 

All the lanthanide(m) triflates are commercially available from the Aldrich Chemical Co. bar Promethium (radioactive) and Cerium (available in its 44 oxidation state). 

The lutetium hahdes (except the fluoride), together with the nitrates, perchlorates, and acetates, are soluble in water. The hydroxide oxide, carbonate, oxalate, and phosphate compotmds are insoluble. Lutetium compounds are all colorless in the solid state and in solution. Due to its closed electronic configuration (4f " ), lutetium has no absorption bands and does not emit radiation. For these reasons it does not have any magnetic or optical importance, see also Cerium Dysprosium Erbium Europium Gadolinium Holmium Lanthanum Neodymium Praseodymium Promethium Samarium Terbium Ytterbium. 

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