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Published in Alina Kabata-Pendias, Barbara Szteke, Trace Elements in Abiotic and Biotic Environments, 2015
Alina Kabata-Pendias, Barbara Szteke
Fluorine, occurring mainly at −1 oxidation state, is a yellow gas, very toxic, and reactive with both organic and inorganic substances. Metallic fluorides are highly toxic, whereas organic fluorides are almost harmless. Its most common mineral, fluorite (also called fluoride or fluorspar), CaF2 is often associated with sellaite, MgF2, and is widely distributed in both lithosphere and hydrosphere. Other common minerals are cryolite, Na3(AlF6); fluorapatite, Ca5(PO4)3F; and topaz, Al2F2SiO4, a popular gemstone, and depending on the addition of some metals may be of various colors.
Properties of the Elements and Inorganic Compounds
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
Name Polymidite Portlandite Powellite Protoenstatite Proustite Pseudowollastonite Pyrargyrite Pyrite Pyrolusite Pyrope Pyrophyllite Pyroxmangite Pyrrhotite Quartz () Quartz () Rammelsbergite Realgar Retgersite Riebeckite Rutile Safflorite Fe-Sanidine Sanmartinite Sapphirine Schorl Selenium (gray) Sellaite Senarmontite Shandite Shortite Siderite Silicon Sillimanite Silver Silver telluride I Silver telluride II Fe-Skutterudite Ni-Skutterudite Smithsonite Sodium melilite Sperrylite Spessartite Sphalerite Sphene Spinel Spodumene Spodumene () Staurolite Sternbergite Stibnite Stilleite Stishovite Stolzite Stromeyerite Sulfur (monoclinic) Sulfur (rhombohedral) Formula Crystal system cubic hexagonal tetragonal orthorhombic rhombohedral triclinic rhombohedral cubic tetragonal cubic monoclinic triclinic hexagonal hexagonal hexagonal orthorhombic monoclinic tetragonal monoclinic tetragonal orthorhombic monoclinic monoclinic monoclinic rhombohedral hexagonal tetragonal cubic rhombohedral orthorhombic rhombohedral cubic orthorhombic cubic cubic cubic cubic cubic rhombohedral tetragonal cubic cubic cubic monoclinic cubic monoclinic tetragonal monoclinic orthorhombic orthorhombic cubic tetragonal tetragonal orthorhombic monoclinic rhombohedral Structure type spinel cadmium iodide scheelite Z a/Å 9.480 3.5933 5.226 9.25 10.816 6.90 11.052 5.4175 4.388 11.459 5.14 7.56 3.440 4.9136 4.999 4.757 9.29 6.782 9.729 4.5937 5.231 8.689 4.691 9.96 16.032 4.3642 4.621 11.152 5.576 4.961 4.6887 5.4305 7.4843 4.0862 5.29 6.585 8.1814 8.3300 4.6528 8.511 5.968 11.621 5.4093 7.07 8.080 9.451 7.5332 7.90 11.60 11.229 5.6685 4.1790 5.4616 4.066 11.04 10.818
Physical Properties of Crystalline Infrared Optical Materials
Published in Paul Klocek, Handbook of Infrared Optical Materials, 2017
James Steve Browder, Stanley S. Ballard, Paul Klocek
Notes: Magnesium fluoride in single-crystal form occurs in nature as the mineral sellaite. It is a hard material with high thermal and mechanical shock resistance. This material is birefringent, has a low refractive index, and is used as an IR polarizer. Diameters up to 6 in. are available. As a polycrystalline optical material, it has been commercially produced as Irtran 1 by Eastman Kodak Co. In this form magnesium fluoride apparently does not exhibit double refraction. (See also data sheet on Irtran 1.)
Silicon Subwavelength Grating Slot Waveguide based Optical Sensor for Label Free Detection of Fluoride Ion in Water
Published in IETE Technical Review, 2023
Kritika Awasthi, Nishit Malviya, Amitesh Kumar
Nowadays, Groundwater contamination analysis is of prime importance for environmental safety. The rapid surge in agricultural and industrial waste leads to a drastic increase in groundwater contamination due to the presence of chemicals such as nitrates, chloride, fluoride, sulfide, bromide, etc. These contaminants create health issues beyond their acceptable limit. Thus, the detection of these chemicals is essential for humanitarian safety and for proper monitoring of the quality of groundwater. Fluoridation of groundwater is a major reason behind groundwater contamination. Natural reasons for higher concentrations of fluoride are volcanic activities, the presence of fluoride-bearing minerals such as fluorite, cryolite, topaz, apatite, amphiboles, micas, sellaite, and villiaumite in sodium-rich (alkaline) igneous rocks [1–4]. There are various human activities such as industrial and agricultural discharges which are responsible for higher concentrations of fluoride in groundwater. Major population in India depends on groundwater for drinking water. Excess fluoride content in drinking water can have severe human health effects such as dental and skeletal fluorosis, yellow teeth, twisted limbs, osteoporosis, cancer, infertility in women, brain damage, Alzheimer's disease, and thyroid disorders [2]. WHO's maximum acceptable limit for fluoride concentration in drinking water is up to 1.5 ppm and beyond this permissible limit, it has been classified as fluoride pollution of groundwater [2,3]. Fluoride contamination is responsible for enormous problems in future; thus, the detection of fluoride is necessary for maintaining optimum drinking water quality for human safety. To analyse the groundwater situation in various hydrogeological environments, parameters such as variation in water levels and water quality have to be monitored. According to a report on groundwater presented by Central Ground Water Board, MER Patna, India for various districts of Jharkhand, India, the groundwater contains various chemical compounds within permissible limits except for fluoride contamination. Figure 1 shows fluoride concentration (ppm) in the Dhanbad region of Jharkhand during 2018–2019, 2017–2018, and 2016–2017 [5–7]. It was reported that in parts of GodharBasti, Gobindpur, Nirsa, and Rajganj fluoride concentration is beyond permissible limits. Thus, detection of such low-concentration fluoride contaminations is necessary for maintaining optimum water quality for drinking. So far various electronic detecting technologies such as UV-VIS spectroscopy, atomic absorption spectroscopy (AAS), emission spectrometer instruments [1,3], etc. are used for the analysis and monitoring of chemicals present in water [1–4]. However, conventional electronic sensor suffers from factors such as temperature variation, being less reliable under high electromagnetic fields or radiation fields, vulnerable, interference from the environment, cost, etc.