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 picture info Silver Iodide Silver iodide is an inorganic compound with the formula AgI. The compound is a bright yellow solid, but samples almost always contain impurities of metallic silver that give a gray coloration. The silver contamination arises because AgI is highly photosensitive. This property is exploited in silver-based photography. Silver iodide is also used as an antiseptic and in cloud seeding. The structure adopted by silver iodide is temperature dependent:[2] Below 420 K, the β phase of AgI, with the wurtzite structure, is most stable. This phase is encountered in nature as the mineral iodargyrite. Above 420 K, the α phase becomes more stable. This motif is a body-centered cubic structure which has the silver centers distributed randomly between 6 octahedral, 12 tetrahedral and 24 trigonal sites.[3] At this temperature, Ag+ ions can move rapidly through the solid, allowing fast ion conduction [...More Info...]       [...Related Items...] CAS Registry Number A CAS Registry Number,[1] also referred to as CASRN or CAS Number, is a unique numerical identifier assigned by the Chemical Abstracts Service (CAS) to every chemical substance described in the open scientific literature (currently including all substances described from 1957 through the present, plus some substances from the early or mid 1900s), including organic and inorganic compounds, minerals, isotopes, alloys and nonstructurable materials (UVCBs, substances of unknown or variable composition, complex reaction products, or biological origin).[2] CASRNs are generally serial numbers (with a check digit), so they do not contain any information about the structures themselves the way SMILES and InChI strings do. The registry maintained by CAS is an authoritative collection of disclosed chemical substance information [...More Info...]       [...Related Items...] Standard State In chemistry, the standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions. A superscript circle is used to designate a thermodynamic quantity in the standard state, such as change in enthalpy (ΔH°), change in entropy (ΔS°), or change in Gibbs free energy (ΔG°).[1][2] (See discussion about typesetting below.) In principle, the choice of standard state is arbitrary, although the International Union of Pure and Applied Chemistry (IUPAC) recommends a conventional set of standard states for general use.[3] IUPAC recommends using a standard pressure p⦵ = 105 Pa.[4] Strictly speaking, temperature is not part of the definition of a standard state. For example, as discussed below, the standard state of a gas is conventionally chosen to be unit pressure (usually in bar) ideal gas, regardless of the temperature [...More Info...]       [...Related Items...] Photosensitivity Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light. In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicity.[1][2] The photosensitive ganglion cells in the mammalian eye are a separate class of light-detecting cells from the photoreceptor cells that function in vision. Photosensitivity occurs in multiple species including sheep, bovine, and horses [...More Info...]       [...Related Items...] Entropy Of Fusion The entropy of fusion is the increase in entropy when melting a substance. This is almost always positive since the degree of disorder increases in the transition from an organized crystalline solid to the disorganized structure of a liquid; the only known exception is helium.[1] It is denoted as ${\displaystyle \Delta S_{\text{fus}}}$ and normally expressed in J mol−1 K−1 A natural process such as a phase transition will occur when the associated change in the Gibbs free energy is negative [...More Info...]       [...Related Items...] picture info Safety Data Sheet A safety data sheet (SDS),[1] material safety data sheet (MSDS), or product safety data sheet (PSDS) are documents that list information relating to occupational safety and health for the use of various substances and products. SDSs are a widely used system for cataloging information on chemicals, chemical compounds, and chemical mixtures. SDS information may include instructions for the safe use and potential hazards associated with a particular material or product, along with spill-handling procedures. The older MSDS formats could vary from source to source within a country depending on national requirements; however, the newer SDS format is internationally standardized. An SDS for a substance is not primarily intended for use by the general consumer, focusing instead on the hazards of working with the material in an occupational setting [...More Info...]       [...Related Items...] picture info Precipitate Precipitation is defined as the creation of a solid from a solution. When the reaction occurs in a liquid solution, the solid formed is called the 'precipitate'. The chemical that causes the solid to form is called the 'precipitant'. Without sufficient force of gravity (settling) to bring the solid particles together, the precipitate remains in suspension. After sedimentation, especially when using a centrifuge to press it into a compact mass, the precipitate may be referred to as a 'pellet'. Precipitation can be used as a medium. The precipitate-free liquid remaining above the solid is called the 'supernate' or 'supernatant'. Powders derived from precipitation have also historically been known as 'flowers'. When the solid appears in the form of cellulose fibers which have been through chemical processing, the process is often referred to as regeneration. Sometimes the formation of a precipitate indicates the occurrence of a chemical reaction [...More Info...]       [...Related Items...] picture info Hydroiodic Acid Hydroiodic acid (or hydriodic acid) is a highly acidic aqueous solution of hydrogen iodide (H I) (concentrated solution usually 48 - 57% HI). It is the second strongest hydrohalic acid, after hydroastatic acid. Hydroiodic acid is a commonly used chemical reagent and is one of the strong acids that ionize completely in an aqueous solution. Hydroiodic acid readily reacts with oxygen in air, contributing to the deep colours associated with old samples; 4 HI + O2 → 2 H2O + 2 I2 HI + I2 → HI3[citation needed] Like other hydrogen halides, hydroiodic acid will perform addition reactions with unsaturated hydrocarbons such as alkenes [...More Info...]       [...Related Items...]