Scandium dissolved

In the course of phase-equilibrium studies in the Sc-Ni-Ge system at 870 K, Kotur and Andrusyak (1991) observed eight ternary nickel germanides of scandium (see fig. 29). For details of sample preparation, see Sc-V-Ge. The binary germanides of scandium dissolve 2-8 at. /o Ni the solubility of Ge in ScNi2 is 3.5 at.% (Kotur 1995). 

Some nut trees accumulate mineral elements. Hickory nut is notable as an accumulator of aluminum compounds (30) the ash of its leaves contains up to 37.5% of AI2O2, compared with only 0.032% of aluminum oxide in the ash of the Fnglish walnut s autumn leaves. As an accumulator of rare-earth elements, hickory greatly exceeds all other plants their leaves show up to 2296 ppm of rare earths (scandium, yttrium, lanthanum, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium). The amounts of rare-earth elements found in parts of the hickory nut are kernels, at 5 ppm shells, at 7 ppm and shucks, at 17 ppm. The kernel of the Bra2d nut contains large amounts of barium in an insoluble form when the nut is eaten, barium dissolves in the hydrochloric acid of the stomach. 

The methodology of a Lewis acid dissolved in an ionic liquid has been used for Friedel-Crafts alkylation reactions. Song [85] has reported that scandium(III) tri-flate in [BMIM][PFg] acts as an alkylation catalyst in the reaction between benzene and hex-l-ene (Scheme 5.1-55). 

Table I. Blank Concentrations for Dissolved Cobalt, Iron, Scandium (ng/mL) Given as Stem-and-Leaf Displays (Tukey 1977) W...

In these procedures 1 litre of seawater was shaken with 60 mg charcoal for 15 min. Complexing agents were added in amounts of 1 mg, dissolved in 1 ml of acetone. The pH was 5.5, or it was adjusted to 8.5 by addition of 0.1 M ammonia. The charcoal was filtered off and irradiated. Results of three sets of experiments with charcoal alone, charcoal in the presence of dithizone, and charcoal in the presence of sodium diethyldithiocarbamate are compared. The following elements are adsorbed to an extent from 75 to 100% silver, gold, cerium, cadmium, cobalt, chromium, europium, iron, mercury, lanthanum, scandium, uranium, and zinc. The amount of sodium is reduced to about 10 6, bromine to about 10 5, and calcium to about 10 2. 

A less specific type of adsorption can sometimes be used if the required product forms insoluble hydroxides but the target element does not. In this case, the solution is made alkaline, and the carrier-free radio-colloidal product is readily absorbed on to filter paper in good yield, when, after washing, it can subsequently be dissolved in acid. This has been used for the separation of magnesium from aluminium, scandium from calcium and for several other elements (17), (26), (42), (44), (66), (103), (104), (105), (106). 

Treatment with hydrochloric acid dissolves scandium and other metals. The solution is treated with sodium thiocyanate and extracted with ether. Scandium converted to its oxide SC2O3 is separated from the solvent extract by ion exchange. 

Question 7.1 (a) Write equations for the (i) reduction of ScFs by calcium, (ii) scandium oxide dissolving in potassium hydroxide solution, (iii) the thermal decomposition of (NH4)3ScCl6. (b) Why is the thermal decomposition of (NH4)3ScCl6 a good way of making pure ScCls ... 

Rare earth nitrates can be prepared using nitric acid to react with a corresponding oxide, hydroxide, carbonate or metal. These nitrates dissolve easily in polar solvents such as water, alcohols, esters or nitriles. They are unstable to heat as the decomposition temperature for the nitrates of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, and samarium are 510,480, 780,450, 505, 830, and 750 °C, respectively. 

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used for the determination of most major and trace elements. The samples are fused in a Claisse semi-automatic fusion device in Pt-Au crucibles with lithium metaborate (4). The fusion product is dissolved in diluted HNO and brought to volume. For trace elements determination the sample is decomposed by HF, HNOg and HCIO. Scandium serves as an internal standard and is added to all samples and solutions. The instrument (product of Jobin Yvon, France)is calibrated using multi-element synthetic standards. The aqueous solutions are nebulized and injected into the heart of a plasma fire ball. A computerized multi-channel vacuum spectrometer has been programmed for multi-element analysis. 

The scandium recovery process is ouUined schematically in Figure 5. The tungsten ore tailings are dissolved in the hydrazin sulfuric reagent, the pH is adjusted to 2.0, and the resulting solution is checked for the presence of ferric ion colorimetrically using the thiocyanate spot test. Any ferric ion content is reduced to the ferrous state by the addition of elemental iron as per the following equation ... 

Scandium (Sc, at. mass 44.96) occurs in its compounds exclusively in the III oxidation state. Some of its chemical properties resemble those of the lanthanides and yttrium. Scandium hydroxide Sc(OH>3 precipitates at a pH as low as 4.8 and dissolves in alkaline medium in this respect scandium resembles aluminium. 

Standard scandium solution 1 mg/ml. Dissolve 0.1530 g of SC2O3 in 10 ml of hot 2 M HCl, and dilute the solution to volume with water in a 100-ml standard flask. Working solutions are obtained by suitable dilutions of the stock with 0.01 M HCl. 

Other hydrated salts include Sc2 (C2 04)3-61120, Sc (N03)3-4H20, and Sc2(S04)3-5H20 the structure of the oxalate shows approximately dodecahedral coordination of scandium by two water molecules and six oxygens from bridging oxalates. The oxalate is, unlike lanthanide oxalates, slightly soluble in water and also dissolves in excess oxalate as 80(0204)2. No structural data are available for the nitrate, although it should be noted that eight-coordinate Sc(N03)3(H20)2 and nine-coordinate Sc(N03)3(H20)3 molecules are present in crown ether... 

Scandium (Sc) exists in the - -3 oxidation state as Sc(OH)3 in sea water. Dissolved scandium has a nutrient-type vertical profile (Figure 5A), with low concentrations at the surface and enrichment at depth, yet no significant interocean fractionation is observed. Scandium was detected by neutron... 

Figure 5 Depth profiles of (A) dissolved scandium in the central North Pacific (solid symbols 28°N 122°W Spencer ef a/., 1970) and in the western North Atlantic (open symbols 36°N 68°W Brewer ef a/., 1972), and (B) dissolved titanium in the North Pacific (solid symbols 50°N 145°W Orians ef a/., 1990) and the western North Atlantic (32°N 64°W Orians efa/., 1990).

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