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Materials Used for General Radiation Detection
Published in Alan Owens, Semiconductor Radiation Detectors, 2019
The hexagonal form of mercuric sulphide (HgS) has received considerable attention as a room-temperature replacement for HgI2, in view of its high density (8.2 g cm–3), favourable bandgap (2.1 eV) and relative chemical stability. HgS can assume two different crystalline forms, – α-HgS, which crystallizes in a trigonal type, hexagonal structure, and β-HgS, which crystallizes in a zincblende type, cubic structure. Alpha-HgS is more commonly recognized as the mineral cinnabar, which happens to be the main commercial source of the metal mercury. It is also widely used as the high-grade paint pigment, vermillion. Recently, it has been explored for acousto-optical [160], infrared sensing [161] and photoelectronic applications [162-164]. Beta-HgS (also known as metacinnabar) is generally considered a semimetal but has recently been shown to be a strong topological insulator [165]. As a bulk material, it has potential for use in low-power consumption electronic devices [165] and in its nano-particle form, in solid-state solar cell and photo-electrochemical cell applications [164]. Interestingly, metacinnabar is the compound form that mercury evolves into in aged amalgam dental fillings.
March of the Pigments: Color History, Science and Impact
Published in Ambix, 2023
The author acknowledges the help of a great many people in the production of the book. Each chapter was read and corrected by different groups of three people, and perhaps this has contributed to the unevenness in style and, to some extent, in content. For example, red cinnabar and vermilion (mercury(II) sulfide, α-HgS) appear in several chapters, as does the black form, metacinnabar (β-HgS). The tendency for red cinnabar to blacken is first mentioned in chapter three, raising the possibility that the red form is reverting to the black form, but this is not cross-referenced with other explanations offered in later chapters. What would have helped is an introductory or concluding chapter providing the links between these separate discussions of cinnabar and other pigments. The proof correction of the book also leaves something to be desired: in addition to the glaring misspelling of Botticelli in the title of chapter nine, numerous other errors remain throughout – a pity, as this spoils what is otherwise an entertaining and useful book.
Humphry Davy’s Early Chemical Knowledge, Theory and Experiments: An Edition of His 1798 Manuscript, “An Essay on Heat and the Combinations of Light” from The Royal Institution of Cornwall, Courtney Library, MS DVY/2
Published in Ambix, 2019
In the Theory of Respiration now generally received Oxygen Gas is assumed to be Oxygen combined with Caloric. Since the Oxygen Gas made use of in Respiration is diminished & Carbonic acid Gas & water formed it is asserted that Oxygen Gas is decomposed in the lungs. It is said that a portion of the Oxygen combines with the iron of the blood oxydates it & gives it a vermilion color. Another portion combines with the carbon of the blood & of the pulmonary mucus to form the Carbonic acid Gas liberated in respiration. Another portion combined with the Hydrogen of the venous blood to form water. The Caloric which was combined with the Oxygen partly combines with the blood now increased in capacity & is partly liberated &c. Without considering my Expts there are the following objections to this Hypothesis. 1st. Iron never decomposes Oxygen Gas at so low a temperature as 98° the greatest heat of the lungs & Oxygen Gas is never decomposed by iron without rapid combustion flame & great heat. 2dly Oxygen Gas is never decomposed by Carbon at so low a temperature as 98° & is never decomposed without the liberation of Light. 3dly. There is never a decomposition of Oxygen Gas by the affinity of Hydrogen at so low a temperature