Concept
Tungsten
Related concepts (43)
Free element
In chemistry, a free element is a chemical element that is not combined with or chemically bonded to other elements. Examples of elements which can occur as free elements include the oxygen molecule (O_2) and carbon. All atoms of free elements have an oxidation number of 0. They hardly ever bond with other atoms. Other examples of free elements include the noble metals gold and platinum.
Metal aromaticity
Metal aromaticity or metalloaromaticity is the concept of aromaticity, found in many organic compounds, extended to metals and metal-containing compounds. The first experimental evidence for the existence of aromaticity in metals was found in aluminium cluster compounds of the type MAl4− where M stands for lithium, sodium or copper. These anions can be generated in a helium gas by laser vaporization of an aluminium / lithium carbonate composite or a copper or sodium / aluminium alloy, separated and selected by mass spectrometry and analyzed by photoelectron spectroscopy.
Phosphotungstic acid
Phosphotungstic acid (PTA) or tungstophosphoric acid (TPA), is a heteropoly acid with the chemical formula . It forms hydrates . It is normally isolated as the n = 24 hydrate but can be desiccated to the hexahydrate (n = 6). EPTA is the name of ethanolic phosphotungstic acid, its alcohol solution used in biology. It has the appearance of small, colorless-grayish or slightly yellow-green crystals, with melting point 89 °C (24 hydrate). It is odorless and soluble in water (200 g/100 ml).