Holmium is a chemical element; it has symbol Ho and atomic number 67. It is a rare-earth element and the eleventh member of the lanthanide series. It is a relatively soft, silvery, fairly corrosion-resistant and malleable metal. Like many other lanthanides, holmium is too reactive to be found in native form, as pure holmium slowly forms a yellowish oxide coating when exposed to air. When isolated, holmium is relatively stable in dry air at room temperature. However, it reacts with water and corrodes readily, and also burns in air when heated.
Selenic acid is the inorganic compound with the formula H2SeO4. It is an oxoacid of selenium, and its structure is more accurately described as O2Se(OH)2. It is a colorless compound. Although it has few uses, one of its salts, sodium selenate is used in the production of glass and animal feeds.
Selenium compounds are compounds containing the element selenium (Se). Among these compounds, selenium has various oxidation states, the most common ones being −2, +4, and +6. Selenium compounds exist in nature in the form of various minerals, such as clausthalite, guanajuatite, tiemannite, crookesite etc., and can also coexist with sulfide minerals such as pyrite and chalcopyrite. For many mammals, selenium compounds are essential. For example, selenomethionine and selenocysteine are selenium-containing amino acids present in the human body. Selenomethionine participates in the synthesis of selenoproteins. The reduction potential and pKa (5.47) of selenocysteine are lower than those of cysteine, making some proteins have antioxidant activity. Selenium compounds have important applications in semiconductors, glass and ceramic industries, medicine, metallurgy and other fields.
Langbeinites are a family of crystalline substances based on the structure of langbeinite with general formula M2M'2(SO4)3, where M is a large univalent cation, and M' is a small divalent cation. The sulfate group, SO2−4, can be substituted by other tetrahedral anions with a double negative charge such as tetrafluoroberyllate, selenate, chromate, molybdate, or tungstates. Although monofluorophosphates are predicted, they have not been described. By redistributing charges other anions with the same shape such as phosphate also form langbeinite structures. In these the M' atom must have a greater charge to balance the extra three negative charges.
Dysprosium acetylacetonate is a chemical compound of dysprosium with formula Dy(C5H7O2)3(H2O)n.
Iron(II) selenate (ferrous selenate) is an inorganic compound with the formula FeSeO4. It has anhydrous and several hydrate forms. The pentahydrate has the structure, [Fe(H2O)4]SeO4•H2O, isomorphous to the corresponding iron(II) sulfate. Heptahydrate is also known, in form of unstable green crystalline solid.
A selenite fluoride is a chemical compound or salt that contains fluoride and selenite anions. These are mixed anion compounds. Some have third anions, including nitrate, molybdate, oxalate, selenate, silicate and tellurate.
A selenate selenite is a chemical compound or salt that contains selenite and selenate anions (SeO32- and SeO42-). These are mixed anion compounds. Some have third anions.
A nitrate nitrite, or nitrite nitrate, is a coordination complex or other chemical compound that contains both nitrite and nitrate anions (NO3− and NO2−). They are mixed-anion compounds, and they are mixed-valence compounds. Some have third anions. Many nitrite nitrate compounds are coordination complexes of cobalt. Such a substance was discovered by Wolcott Gibbs and Frederick Genth in 1857.
Europium compounds are compounds formed by the lanthanide metal europium (Eu). In these compounds, europium generally exhibits the +3 oxidation state, such as EuCl3, Eu(NO3)3 and Eu(CH3COO)3. Compounds with europium in the +2 oxidation state are also known. The +2 ion of europium is the most stable divalent ion of lanthanide metals in aqueous solution. Many europium compounds fluoresce under ultraviolet light due to the excitation of electrons to higher energy levels. Lipophilic europium complexes often feature acetylacetonate-like ligands, e.g., Eufod.
Terbium compounds are compounds formed by the lanthanide metal terbium (Tb). Terbium generally exhibits the +3 oxidation state in these compounds, such as in TbCl3, Tb(NO3)3 and Tb(CH3COO)3. Compounds with terbium in the +4 oxidation state are also known, such as TbO2 and BaTbF6. Terbium can also form compounds in the 0, +1 and +2 oxidation states.
Praseodymium(III) selenate is an inorganic compound, the salt of praseodymium and selenic acid with the chemical formula Pr2(SeO4)3. It forms green crystals when hydrated.
Samarium(III) perchlorate is an inorganic compound with the chemical formula Sm(ClO4)3.
Iodate sulfrates are mixed anion compounds that contain both iodate and sulfate anions. Iodate sulfates have been investigated as optical second harmonic generators, and for separation of rare earth elements. Related compounds include the iodate selenates and chromate iodates.
Thulium(III) selenate is an inorganic compound, with the chemical formula Tm2(SeO4)3. It can be obtained by reacting a thulium(III) oxide and selenic acid solution and crystallizing it. It crystallises with ammonium selenate in an aqueous solution to obtain NH4Tm(SeO4)2·3H2O.
Nickel(II) selenate is a selenate of nickel with the chemical formula NiSeO4.
Erbium(III) selenate is an inorganic compound, with the chemical formula Er2(SeO4)3. It exists as an anhydrate or an octahydrate.
Cerium(IV) selenate is an inorganic compound with the chemical formula Ce(SeO4)2.
Zirconium selenate is an inorganic compound with the chemical formula Zr(SeO4)2. Its tetrahydrate can be obtained by the reaction of selenic acid and a saturated aqueous solution of zirconium oxychloride octahydrate (or zirconium hydroxide). The tetrahydrate belongs to the orthorhombic crystal system and is isostructural with Zr(SO4)2·4H2O. It loses water when heated and becomes anhydrous at 580 °C. It reacts with potassium fluoride to obtain K2Zr(SeO4)2F2·3H2O.
Cerium(III) selenate is an inorganic compound with the chemical formula Ce2(SeO4)3. It can be obtained by reacting selenic acid and cerium(III) carbonate, and the solvent is evaporated to precipitate crystals. Mix cerium selenate and cesium selenate in an aqueous solution, evaporate and crystallize to obtain The double salt CsCe(SeO4)2·4H2O can be obtained from mixing cerium(III) selenate and cesium selenate in an aqueous solution, and then evaporating and crystallizing the solution.
