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White phosphorus, yellow phosphorus, or simply tetraphosphorus (P 4) is an allotrope of phosphorus.It is a translucent waxy solid that quickly yellows in light (due to its photochemical conversion into red phosphorus), [2] and impure white phosphorus is for this reason called yellow phosphorus.
White phosphorus (left), red phosphorus (center left and center right), and violet phosphorus (right) White phosphorus and resulting allotropes Elemental phosphorus can exist in several allotropes, the most common of which are white and red solids.
Historically, before the development of mineral-based extractions, white phosphorus was isolated on an industrial scale from bone ash. [71] In this process, the tricalcium phosphate in bone ash is converted to monocalcium phosphate with sulfuric acid: Ca 3 (PO 4) 2 + 2 H 2 SO 4 → Ca(H 2 PO 4) 2 + 2 CaSO 4
Phosphor thermometry is a temperature measurement approach that uses the temperature dependence of certain phosphors. For this, a phosphor coating is applied to a surface of interest and, usually, the decay time is the emission parameter that indicates temperature.
Quantities, Units and Symbols in Physical Chemistry, also known as the Green Book, is a compilation of terms and symbols widely used in the field of physical chemistry. It also includes a table of physical constants , tables listing the properties of elementary particles , chemical elements , and nuclides , and information about conversion ...
The British imperial system uses a stone of 14 lb, a long hundredweight of 112 lb and a long ton of 2,240 lb. The stone is not a measurement of weight used in the US. The US customary system uses the short hundredweight of 100 lb and short ton of 2,000 lb. Where these systems most notably differ is in their units of volume.
[a] This system underlies the International System of Units (SI) [b] but does not itself determine the units of measurement used for the quantities. The system is formally described in a multi-part ISO standard ISO/IEC 80000 (which also defines many other quantities used in science and technology), first completed in 2009 and subsequently ...
The SI system after 1983, but before the 2019 revision: Dependence of base unit definitions on other base units (for example, the metre is defined as the distance travelled by light in a specific fraction of a second), with the constants of nature and artefacts used to define them (such as the mass of the IPK for the kilogram).