Thorium determination

Thorium, determination by x-ray emission spectrography, 199, 329 together with that of uranium by radioactivity and x-ray emission spectrography, 209... 

Uranium (and thorium) was also detected by LA-ICP-MS in human brain samples (thin sections of hippocampus73) and protein spots of human brain separated by 2D gel electrophoresis.87 The detection limits for uranium and thorium determination in thin sections of brain tissues were determined as lOngg-1. Figure 9.52 shows transient signals of 238U+ in protein spots 9a and 9d from a human brain sample (somatomotor cortex) measured by LA-ICP-MS. Protein spots were separated by 2D gel electrophoresis are illustrated.87... 

The methods range from simple, inexpensive absorption spectroscopy to sophisticated tunable-laser-excited fluorescence and ionization spectroscopies. AAS has been used routinely for uranium and thorium determinations (see for example Pollard et al., 1986). The technique is based on the measurement of absorption of light by the sample. The incident light is normally the emission spectrum of the element of interest, generated in a hollow-cathode lamp. For isotopes with a shorter half life than and Th, this requires construction of a hollow-cathode lamp with significant quantities of radioactive material. Measurement of technetium has been demonstrated in this way by Pollard et al. (1986). Lawrenz and Niemax (1989) have demonstrated that tunable lasers can be used to replace hollow-cathode lamps. This avoids the safety problems involved in the construction and use of active hollow-cathode lamps. Tunable semiconductor lasers were used as these are low-cost devices. They do not, however, provide complete coverage of the spectral range useful for AAS and the method has, so far, only been demonstrated for a few elements, none of which were radionuclides. 

On the basis of results obtained the possibility of thorium determination in the presence of five-fold excess of rare earths was stated by means of HMDTA titration and h.f.t. detection of the equivalent point. 

LOV—MSFIA—ICP-MS system for uranium and thorium determination. CC central conduit, FIC holding coil. IV injection valve, RC reaction coil. 

FIA—ICP-MS system for uranium and thorium determination. IV injection valve. 

T. Kiliari, I. Pashalidis, Thorium determination in aqueous solutions after separation hy ion-exchange and liquid extraction, J. Radioanal. Nucl. Chem. 288 (2011) 753—758. 

Uranium and thorium are the first members of natural radioactive chain which makes their determination in natural materials interesting from geochemical and radioecological aspect. They are quantitatively determined as elements by spectrophotometric method and/or their radioisotopes by alpha spectrometry. It is necessary to develop inexpensive, rapid and sensitive methods for the routine researches because of continuous monitoring of the radioactivity level. 

Curie chose for her dissertation research the new topic of uranium rays, a phenomenon that had only recently been observed by Henri Becqiierel. The mystery was the source of the energy that allowed uranium salts to expose even covered photographic plates. Curie s first efforts in the field were systematic examinations of numerous salts to determine which salts might emit rays similar to those of Becquerel s uranium. After discovering that both thorium and uranium were sources of this radiation. Curie proposed the term radioactive to replace uranium rays. She also discovered that the intensity of the emissions depended not on the chemical... 

Determination of cerium as cerium(IV) iodate and subsequent ignition to cerium(IV) oxide Discussion. Cerium may be determined as cerium(IV) iodate, Ce(I03)4, which is ignited to and weighed as the oxide, Ce02. Thorium (also titanium and zirconium) must, however, be first removed (see Section 11.44) the method is then applicable in the presence of relatively large quantities of lanthanides. Titrimetric methods (see Section 10.104 to Section 10.109) are generally preferred. 

Determination of thorium as sebacate and subsequent ignition to the oxide, ThOa Discussion. This procedure permits of the separation by a single precipitation of thorium from relatively large amounts of the lanthanides (Ce, La, Pr, Nd, Sm, Gd) and also from cerium(IV). 

Fluoride, in the absence of interfering anions (including phosphate, molybdate, citrate, and tartrate) and interfering cations (including cadmium, tin, strontium, iron, and particularly zirconium, cobalt, lead, nickel, zinc, copper, and aluminium), may be determined with thorium chloranilate in aqueous 2-methoxyethanol at pH 4.5 the absorbance is measured at 540 nm or, for small concentrations 0-2.0 mg L 1 at 330 nm. 

Glocker and Frohnmayer determined the characteristic constant c for nine elements (Reference 2, Table 4) ranging in atomic numbers from 42 (molybdenum) to 90 (thorium). They proved that identical results could be obtained with the sample in the primary (polychromatic) or in the diffracted (monochromatic) beam. The method was applied with good results to the determination of barium in glass of antimony in a silicate of hafnium in the mineral alvite and of molybdenum, antimony, barium, and lanthanum in a solution of their salts—for example, 5.45% barium was found on 90-minute exposure by the x-ray method for a glass that yielded 5.8% on being analyzed chemically. 

An interesting variant of Group I is the determination of thorium in monazite concentrates.73 Here the variations that may occur in the chemical composition of the matrix leave its x-ray absorbance virtually unaltered. This simplicity is possible because the principal individual rare-earth elements present in the samples lie in the range of atomic numbers from 57 to 60, a range so small as to preclude marked variations in the over-all mass absorption coefficient. 

On the basis of these facts, it was speculated that plutonium in its highest oxidation state is similar to uranium (VI) and in a lower state is similar to thorium (IV) and uranium (IV). It was reasoned that if plutonium existed normally as a stable plutonium (IV) ion, it would probably form insoluble compounds or stable complex ions analogous to those of similar ions, and that it would be desirable (as soon as sufficient plutonium became available) to determine the solubilities of such compounds as the fluoride, oxalate, phosphate, iodate, and peroxide. Such data were needed to confirm deductions based on the tracer experiments. 

U1 "1" (16), and Np1 "1" (17) (Table IV). Only in the thorium system have stability constants been determined as a function of acidity. Zebroski et al., (12) found that the 1 2 complex had the form TMSOi, at 0.5 M and 1.0 M acidity but suggested a contribution from the monoprotonated, bis-sulfato complex in 2 M acid. However, Zielen (9) found no evidence for such a species. The Kj/K2 ratio found in the latter study (n.8) compares favorably with the Am(III)-S0 data of DeCarvalho and Choppin (10)... 

Determine the particle emitted and write the balanced nuclear equation for each of the following nuclear transformations (a) carbon-14 to nitrogen-14 (b) neon-19 to fluorine-19 (c) gold-188 to platinum-188 (d) uranium-229 to thorium-225. 

C22-0035. Determine Z, A, and N for each of the following nuclides (a) the helium nuclide with one less neutron than proton (b) the nuclide of barium whose neutron-proton ratio is 1.25 and (c) the nuclide of thorium that contains 1.5 times as many neutrons as protons. 

Douglas investigated heats of formation of dimethyl sulphoxide (and also of the sulphone) and proposed in a footnote that it could be determined by 5-min reaction with potassium permanganate/sulphuric acid, then adding excess iron(II) sulphate and finally titrating with permanganate. The same principle was used by Krishnan and Patel to determine dimethyl sulphoxide in various complexes (with perchlorates of titanyl, zirconyl and thorium), and by Krull and Friedmann to determine the same compound but using only dilute sulphuric acid and 5-min reaction. 

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