Lutetium fluoride

Lutetium fluoride is a skin irritant, and its fumes are toxic if inhaled. The dust and powder of the oxides of some rare-earths, including lutetium, are toxic if inhaled or ingested. 

Lutetium is produced commercially from monazite. The metal is recovered as a by-product during large-scale extraction of other heavy rare earths (See Cerium, Erbium, Holmium). The pure metal is obtained by reduction of lutetium chloride or lutetium fluoride by a alkali or alkaline earth metal at... 

Lutetium is the most difficult lanthanoid to obtain in pure form. The usual method used begins with either lutetium fluoride (LUF3) or lutetium chloride (LUCI3). An active metal, such as sodium (Na) or potassium (K) is then added to LUF3 or LUCI3 to obtain pure lutetium. For example ... 

In aqueous media lutetium occurs as tripositive Lu3+ ion. All its compounds are in +3 valence state. Aqueous solutions of all its salts are colorless, while in dry form they are white crystalline solids. The soluble salts such as chloride, bromide, iodide, nitrate, sulfate and acetate form hydrates upon crystallization. The oxide, hydroxide, fluoride, carbonate, phosphate, and oxalate of the metal are insoluble in water. The metal dissolves in acids forming the corresponding salts upon evaporation of the solution and crystallization. 

The solubility of rare earth fluorides REF3 is very low, the pXsp ranges from 19 to 15 for lighter rare earth lanthanum, cerium, praseodymium, and neodymium to heavier rare earth ytterbium and lutetium, respectively. 

Structure Non-hydrated rare earth fluorides have two different crystal systems, a hexagonal system (lanthanum to terbium) and an orthorhombic system (dysprosium to lutetium, yttrium). In the crystal of LaFs, the central ion is nine coordinated by nine fluoride atoms. Each fluoride atom further connects with two lanthanum atoms through a [13-bridge to form an infinite polymer. 

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. 

Marked differences are observed between the properties of the halides. The trifluorides are stable in air at room temperature and are non-hydroscopic. They are sparingly soluble in water with solubility product constants which vary from 10 for lanthanum to 10 for lutetium (DaDilva and Queimado, 1973). In liquid HF, the solubilities are less than 4x 10 mole/ (Ikrami et al., 1972). At high temperatures the trifluorides react with oxygen and moisture to form the oxide fluorides, ROF, which are stable in air at temperatures greater than 1000°C. Conversion of the fluorides to the oxides may be achieved by heating in steam at 1000°C (Stezowski and Eick, 1970). 

Dehydration of the dehydrated trihalides is a final method for oxide conversion. The hydrated trichlorides, tribromides and triiodides, RXj- H20, are obtained by dissolution of the oxides in aqueous hydrohalic acid and condensation by warming and desiccation (Ashcroft and Mortimer, 1968 Brown et al., 1968). The hydrated trifluorides are prepared by dissolution of the oxide in HNO3 or HCl and precipitation with aqueous HF. The filtered trifluoride may be dehydrated by heating slowly to 600°C in an inert gas stream or in vacuum (Strizhkov et al., 1972). Products obtained by heating in air are contaminated with oxide fluoride (Batsanova, 1971). Thermal decomposition studies of the hydrated trichlorides, cf. section 5.1, have shown that the oxide chlorides are readily formed, but careful dehydration under N2 flow has apparently been successful for the chlorides (Ashcroft and Mortimer, 1968). Tribromides have also been prepared by careful vacuum dehydration, but the lutetium products were contaminated with oxide bromide (Brown et al., 1968). In general simple dehydration becomes increasingly difficult with increasing atomic number of both the lanthanide and the halide. 

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