Holmium determination

The wavelength scale of a UV/visible spectrophotometer is checked by determining the specified wavelength maxima of a 5% w/v solution of holmium perchlorate. Figure 4.6 shows the spectrum of holmium perchlorate, the tolerances for ealibration wavelengths specified by the BP are 241.15 1 nm, 287.15 1 nm and 361.5 1 nm. 

Notice that Moseley had made a minor mistake in the atomic number determinations of both holmium and dysprosium. The atomic number of holmium is namely 67, and dysprosium has an atomic number of 66. It also appears that Moseley attached some credence to the investigation of Auer von Welsbach who had demonstrated the complexity of thulium in 1911 by splitting it into three components. Moseley had incorporated two of these components (Tml and Tmll) in his atomic number sequence. Moseley therefore ascribed Urbain s neo-ytterbium and lutetium too high an atomic number (in reality the atomic numbers of ytterbium and... 

Lanthanide (III) Oxides. The lanthanide(III) oxides will be used to illustrate the present breadth of our most extensive knowledge of the chemical thermodynamics of lanthanide compounds. Cryogenic heat capacities of hexagonal (III) lanthanum, neodymium, and samarium oxides, together with those of cubic (III) oxides of gadolinium, dysprosium, holmium, erbium, and ytterbium, have been reported (90, 91, 195). In addition, those of thulium, lutetium, and a composition approaching that of cerium (III) oxide have also been determined, and five well-characterized compositions between PrOi.714 and PrOi.833 are currently under study (J93). 

Only one naturally occurring isotope of holmium exists holmium-165. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element s name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. 

Biborides of holmium and thulium have been prepared from the elements.332 They belong to the same class of structures as A1B2. The structures of HoCo2B2, PrCo2B2, and Y bCo3B2 have also been determined.333... 

The lanthanide or rare earth elements (atomic numbers 57 through 71) typically add electrons to the 4f orbitals as the atomic number increases, but lanthanum (4f°) is usually considered a lanthanide. Scandium and yttrium are also chemically similar to lanthanides. Lanthanide chemistry is typically that of + 3 cations, and as the atomic number increases, there is a decrease in radius for each lanthanide, known as the lanthanide contraction. Because bonding within the lanthanide series is usually predominantly ionic, the lanthanide contraction often determines the differences in properties of lanthanide compounds and ions. Lanthanide compounds often have high coordination numbers between 6 and 12. see also Cerium Dysprosium Erbium Europium Gadolinium Holmium Lanthanum Lutetium Praseodymium Promethium Samarium Terbium Thulium Ytterbium. 

Several new isocyanide complexes of chromium(m) have been prepared by the electrochemical reduction of heavy-metal adducts of chromium(iii) aquocyano-complexes, and characterized by their visible spectra. The chromium 2p- and 3s-orbital ionization potentials in K3[Cr(NCS)6] have been reported, and the lattice parameters for this anion in the salt with diaquotris-(nicotinic acid)holmium(iii) determined. " The absorption spectra of the... 

A complex of holmium perchlorate coordinated with 1-glutamic acid was prepared with a purity of 98.96%. The compound was characterized by chemical, elemental and thermal analysis. Molar heat capacities of the compound were determined by a high-precision automated adiabatic calorimeter from 78 to 370 K. The dehydration temperature, dehydration enthalpy, entropy and the standard enthalpy of formation were reported [183],... 

A Ho(PDC)3(o-phen) complex has been obtained and studied by Xie et al. [184] from the reaction of hydrated holmium chloride, ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen-H20) in absolute ethanol. The enthalpy of complex formation from a solution of the reagents and the molar heat capacity of fre complex were determined by using a heat conduction microcalorimeter. The enthalpy of complex formation from the reaction of the reagents in the solid phase, was calculated on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. The thermodynamics of formation of the complex were investigated by the reaction in solution at the temperature range of 292.15 - 301.15 K. The constant-volume combustion energy of the complex, Act/, was also determined. 

For detectors with built-in holmium oxide filter we recommend in principle to use this filter. However, the determination of the UV absorption maxima of holmium oxide requires a good optical resolution (better than 2nm). Many HPLC detectors are built with a fixed slit of 8-10 nm bandwidth which is inadequate for this task. In case of doubt it is best to ask the manufacturer or to use anthracene. 

Although the crystal structures of about half of the rare earth metals were well established by the mid- to late 1930 s the work by Klemm and Bommer (1937) stands as a landmark paper because they determined the crystal structures and the lattice parameters of all the lanthanides, except holmium, samarium and radioactive promethium. In so doing they... 

In this chapter, a correlation between the ionic radius of the metal-complexing in double-decker phthalocyanines and positions of maxima Q-bands in the electronic absorption spectra were determined in dimethylformamide and chloroform. The increasing of ionic radius from holmium to lutetium caused a regular change in the position of the maxima Q-bands in the absorption spectra. The behavior of metal diphthalocyaninates in supramolecular systems was also investigated. It was revealed that a new band shifted to the red region appeared in absorption spectra of sandwich phthalocyaninates of lutetium, etbium and ytteibium in albumin solution. This particular behavior allows us to consider phthalocyanines as prototype of sensitive biosensor system. 

Because copper has only two stable isotopes, only one tracer isotope is available, which limits the choice of techniques for metabolic studies substantially. In most human studies, Cu has been used to determine apparent absorption, as the difference between the amount of isotope ingested and the amount recovered in feces. To check for completeness of fecal collection, holmium has been suggested and successfully used as a non-absorbable, quantitative elemental marker in copper absorption studies [259]. Studies comparing copper absorption of foods intrinsically or extrinsicaUy labeled with Cu are limited. Johnson and co-workers [260, 261] found no statistically significant difference in copper absorption from intrinsically and extrinsicaUy labeled goose fiver, goose breast, peanut butter, and wheat. Harvey et al. [262] observed significant differences in copper absorption between intrinsically and extrinsicaUy labeled sunflower seeds and soy beans. 

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