Scandium determination

Scandium, determination by x-ray emission spectrography, 328 Scattered x-ray line in background as reference standard in x-ray emission spectrography, 173, 191, 211, 234... 

Saponins la 7,411,430 -, bioautographic determination la 109 Sarcosine Ia435 lbl24 Scandium cations, detection la 144 Scanner, optical trains la 30,39 S-Chamber (small chamber) la 126,127 SCHiFF s bases lb 52 Scintillators la 12 Scopolamine lb 231,252,255,323 Scopoletin lb 216-218,365 Screening process lb 45 Sebacic acid la 178,233,249,308 Sebuthylazine lb 418 Selectivity, enhancement by derivatiza-tion la 55... 

The application of the Chelex 100 resin separation and preconcentration, with the direct use of the resin itself as the final sample for analysis, is an extremely useful technique. The elements demonstrated to be analytically determinable from high salinity waters are cobalt, chromium, copper, iron, manganese, molybdenum, nickel, scandium, thorium, uranium, vanadium, and zinc. The determination of chromium and vanadium by this technique offers significant advantages over methods requiring aqueous final forms, in view of their poor elution reproducibility. The removal of sodium, chloride, and bromide allows the determination of elements with short and intermediate half-lives without radiochemistry, and greatly reduces the radiation dose received by personnel. This procedure was successfully applied in a study of... 

In subsequent studies, methyl vinyl ketone (2.0 mmole) was chosen as the dienophile so as to determine the combined effect of the ionic liquid (2 mL) and the Lewis acids (0.2 and 0.5 wt%) upon the yield and selectivity. Without the Lewis acid catalyst, this system demonstrated a 52% conversion of the cyclopentadiene (2.2 mmol) in 1 h with the endojexo selectivity being 85/15. The cerium triflate-catalyzed reaction was quantitative in 5 min and the endo. exo selectivity was very good for this experiment as well (94 6, endo. exo). Also with the scandium or yttrium salts tested, reactions came to completion in a short time with high stereo-selection. Cerium, scandium and yttrium triflates are strong Lewis acids known to be quite effective catalysts in the cycloadditions of cyclopentadiene with acyclic aldehydes, ketones, quinones and cycloalkenones. These compounds are expected to act as strong Lewis acids because of their hard character and the electron-withdrawing triflate group. On the other hand, reaction times of 1 hour were required for... 

The effective metal valences that were determined by high-energy spectroscopic studies in some of these compounds show that scandium,111 the smallest and most electronegative metal of the series, seems to transfer less electrons to the cage than... 

Sc(OEP)C>2CMe is 0.4 s, which is the longest for any porphyrin, while the fluorescent yield of 0.2 is very high. The radiative properties are explained in terms of covalent interactions between the metal and the ring as modified by the probable location of the metal ion above the porphyrin plane.24 Scandium OEP complexes are reduced to the a, y-dihydro derivatives on reduction with sodium anthracenide and methanol.25 The redox potentials of Sc(OEP)OH have been determined by cyclic voltammetry to be ligand oxidation in PrCN, 1.03 and 0.70 ligand reduction in DMSO, —1.54 (Ey2 values in V vs. SCE) no metal redox wave was observed.26... 

The complexation constants Ki for interaction of Sc3+ ions with substituted and unsubstituted carboxylates in aqueous solution have been determined potentiometrically at 25 °C and 0.1 MKN03 ionic background. They are listed in Table 1, the AH values being derived with the aid of additional measurements at 40°C.61 These values for scandium are greater than those for the lanthanides by roughly one order of magnitude.62... 

Scandium complexes readily with 8-hydroxyquinolinate ion. Many years ago, Sc(hq)3-Hhq, which was obtained from aqueous solution, was described,97 and this compound does not lose Hhq cleanly on heating but does so in benzene solution.98 However, it has been stated that the solid deposited at about pH 7 is in fact Sc(hq)3." More recently, stability constant values have been determined for the Sc3+/hq-/50% aqueous dioxane system and the corresponding 2-methyl-8-hydroxyquinoline system.100 Chinese workers, who are showing some interest in spectrophotometric analysis, have detected Sc3+ on the microgram scale by fluorometry using -5-sulfonate and cetyltrimethylammonium bromide as an extractant... 

The remarkable correlation of iron and scandium observed in a number of potsherds and clays in the Near East has led us to determine this ratio routinely in all our materials and to study its statistical properties. Two examples show the dramatic improvement in the reduction of the standard deviation (expressed as percent) when one considers the Sc/Fe ratio vs. the values of the individual elements. 

The best indicator for use in acidic media from 0.1 M HN03 up to pH 5.6 is xylenol orange (XO 44). Direct determinations can be made of cadmium and cobalt (at 60 °C), copper (in the presence of phen), lead and zinc, scandium, indium, yttrium and the lanthanons, zirconium, hafnium and thorium. Many other elements that block the indicator can be determined indirectly. Consecutive titrations such as Bi (at pH 2) and Pb (at pH 5.5) can be carried out in the same solution and the colour change for the latter is particularly sharp from an intense reddish violet to lemon yellow. The extensive literature on this indicator is reviewed in several places. 2>4>76.87... 

Elements determined but sometimes overlooked antimony, arsenic, bismuth, cadmium, coball, gallium, indium, lanthanum, nickel, palladium. rare earlhs (except cerium), rhodium, ruthenium, scandium, silver, tellurium, thallium, tin. and yttrium. 

Neutron activation analysis has been used to determine scandium, as discussed under Multi-Metal Analysis of Soils in Sect. 2.55. Scandium has also been determined by atomic absorption spectrometry (Sect. 2.55). 

The elements after the rare gas argon all have an inner group of electrons called the argon core and, in addition, outer electrons that determine the chemical properties of the elements. After both the 4s and 3d subsheiis are filled at zinc, the next electron goes into the 4p subshell. The elements from scandium to nickel having incomplete inner (3d) subshells comprise the first row of transition elements. The "discontinuities in the order of... 

The ground state configuration of lanthanides, 4/" l5d 6s2 or 4/"6s2 does not determine the chemical behaviour of these elements. In forming Ln3+ ions, an / electron is removed. Lanthanides differ from transition elements in that 4/ orbitals are shielded and are not available for reactions. Thus lanthanides resemble more closely alkaline earths and the scandium group than transition elements in their chemistry. 

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