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Mercury (element)
Mercury is a chemical element; it has Symbol (chemistry), symbol Hg and atomic number 80. It is commonly known as quicksilver. A Heavy metal element, heavy, silvery d-block element, mercury is the only metallic element that is known to be liquid at standard temperature and pressure; the only other element that is liquid under these conditions is the halogen bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature. Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide). The red pigment vermilion is obtained by Mill (grinding), grinding natural cinnabar or synthetic mercuric sulfide. Exposure to mercury and mercury-containing organic compounds is toxic to the nervous system, immune system and kidneys of humans and other animals; mercury poisoning can result from exposure to water-soluble forms of mercury (such as mercuric chloride or methylmercury) either directly or through mechanisms of biomagnification. Mercu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Element
A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its atomic nucleus, nucleus. Atoms of the same element can have different numbers of neutrons in their nuclei, known as isotopes of the element. Two or more atoms can combine to form molecules. Some elements form Homonuclear molecule, molecules of atoms of said element only: e.g. atoms of hydrogen (H) form Diatomic molecule, diatomic molecules (H). Chemical compounds are substances made of atoms of different elements; they can have molecular or non-molecular structure. Mixtures are materials containing different chemical substances; that means (in case of molecular substances) that they contain different types of molecules. Atoms of one element can be transformed into atoms of a different element in nuclear reactions, which change an atom's at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nervous System
In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events. Nervous tissue first arose in Ediacara biota, wormlike organisms about 550 to 600 million years ago. In Vertebrate, vertebrates, it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers, or axons, that connect the CNS to every other part of the body. Nerves that transmit signals from the brain are called motor nerves (efferent), while those nerves that transmit information from the body to the CNS are called sensory nerves (aff ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercury Relay
A mercury relay (mercury displacement relay, mercury contactor) is a relay that uses mercury as the switching element. They are used as high-current switches or contactors, where contact erosion from constant cycling would be a problem for conventional relay contacts. Owing to environmental considerations about the toxicity of mercury, mercury relays are mostly obsolete, though modern encapsulated units still have applications. They are generally being replaced by solid state relays. Operation Mercury relays consist of a vertical (usually glass) tube containing liquid mercury. They have isolated contacts at the bottom of the tube and partway up, usually in a side arm of the glass. The relay works by displacement. A pool of mercury fills the lower portion of the tube, but is insufficient to bridge the contacts. A magnetic slug of iron or steel is placed in the tube, where it sinks by gravity so as to displace the mercury. The displaced mercury rises in the tube, sufficiently ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercury Switch
A mercury switch is an electricity, electrical switch that opens and closes a electrical circuit, circuit when a small amount of the liquid metal mercury (element), mercury connects metal electrodes to close the circuit. There are several different basic designs (tilt, displacement, radial, etc.) but they all share the common design strength of non-eroding switch contacts. The most common is the ''mercury tilt switch''. It is in one state (open or closed) when tilted one direction with respect to horizontal, and the other state when tilted the other direction. This is what older style thermostats used to turn a heater or air conditioner on or off. The ''mercury displacement switch'' uses a 'plunger' that dips into a pool of mercury, raising the level in the container to contact at least one electrode. This design is used in relays in industrial applications that need to switch high current loads frequently. These relays use electromagnetic coils to pull steel sleeves inside her ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Float Valve
A ballcock (also balltap or float valve) is a mechanism or machine for filling water tanks, such as those found in flush toilets, while avoiding overflow and (in the event of low water pressure) backflow. The modern ballcock was invented by José Antonio de Alzate y Ramírez, a Mexican priest and scientist, who described the device in 1790 in the ''Gaceta de Literatura Méxicana''. The ballcock device was patented in 1797 for use in steam engines by Edmund Cartwright. It consists of a valve connected to a hollow, sealed float by means of a lever mounted near the top of the tank. The float is often ball-shaped, hence the name ''ballcock''. The valve is connected to the incoming water supply, and is opened and closed by the lever which has the float mounted on the end. When the water level rises, the float rises with it; once it rises to a pre-set level, the mechanism forces the lever to close the valve and shut off the water flow. This is an example of negative feedback ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sphygmomanometer
A sphygmomanometer ( ), also known as a blood pressure monitor, blood pressure machine, or blood pressure gauge, is a device used to measure blood pressure, composed of an inflatable cuff to collapse and then release the artery under the cuff in a controlled manner, and a mercury or aneroid manometer to measure the pressure. Manual sphygmomanometers are used with a stethoscope when using the auscultatory technique. A sphygmomanometer consists of an inflatable cuff, a measuring unit (the mercury manometer, or aneroid gauge), and a mechanism for inflation which may be a manually operated bulb and valve or a pump operated electrically. Etymology The word ''sphygmomanometer'' uses the combining form of '' sphygmo-'' + '' manometer''. The roots involved are as follows: Greek ''sphygmos'' "pulse", plus the scientific term '' manometer'' (from French ''manomètre''), i.e. "pressure meter", itself coined from ''manos'' "thin, sparse", and ''metron'' "measure". Most sphygmom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manometer
Pressure measurement is the measurement of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure mechanically are called pressure gauges, vacuum gauges or compound gauges (vacuum & pressure). The widely used Bourdon gauge is a mechanical device, which both measures and indicates and is probably the best known type of gauge. A vacuum gauge is used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (for instance, −1 bar or −760 mmHg equals total vacuum). Most gauges measure pressure relative to atmospheric pressure as the zero point, so this form of reading is simply referred to as "gauge pressure". However, anything greater than total vacuum is technically a form of pressure. For very low pres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barometer
A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis to help find surface Trough (meteorology), troughs, pressure systems and weather front, frontal boundaries. Barometers and pressure altimeters (the most basic and common type of altimeter) are essentially the same instrument, but used for different purposes. An altimeter is intended to be used at different levels matching the corresponding atmospheric pressure to the altitude, while a barometer is kept at the same level and measures subtle pressure changes caused by weather and elements of weather. The average atmospheric pressure on the Earth's surface varies between 940 and 1040 hPa (mbar). The average atmospheric pressure at sea level is 1013 hPa (mbar). Etymology The word ''wikt:barometer, barometer'' is derived from the Ancient Gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermometer
A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer or the pyrometric sensor in an infrared thermometer) in which some change occurs with a change in temperature; and (2) some means of converting this change into a numerical value (e.g. the visible scale that is marked on a mercury-in-glass thermometer or the digital readout on an infrared model). Thermometers are widely used in technology and industry to monitor processes, in meteorology, in medicine (''medical thermometer''), and in scientific research. A standard scale While an individual thermometer is able to measure degrees of hotness, the readings on two thermometers cannot be compared unless they conform to an agreed scale. Today there is an absolute thermodynamic temperature scale. Internat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biomagnification
Biomagnification, also known as bioamplification or biological magnification, is the increase in concentration of a substance, e.g a pesticide, in the tissue (biology), tissues of organisms at successively higher levels in a food chain. This increase can occur as a result of: * Persistence – where the substance cannot be broken down by environmental processes. * Food chain bioenergetics, energetics – where the substance's concentration increases progressively as it moves up a food chain. * Low or non-existent rate of internal degradation or excretion of the substance – mainly due to water-insolubility. Biological magnification often refers to the process whereby substances such as pesticides or heavy metals work their way into lakes, rivers and the ocean, and then move up the food chain in progressively greater concentrations as they are incorporated into the diet of aquatic organisms such as zooplankton, which in turn are eaten perhaps by fish, which then may be eaten by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methylmercury
Methylmercury is an organometallic cation with the formula . It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a bioaccumulative environmental toxicant with a 50-day half-life. Methylmercury (derived biologically from dimethylmercury) is the causative agent of the infamous Minamata disease. Methylmercury is designated as a "priority hazardous substance" according to the Directive on Environmental Quality Standards (Directive 2013/39/EU). Structure and chemistry "Methylmercury" is a shorthand for the hypothetical "methylmercury cation", sometimes written ''methylmercury(1+) cation'' or ''methylmercury(II) cation''. This functional group is composed of a methyl group Chemical bond, bonded to an atom of Mercury (element), mercury. Its chemical formula is (sometimes written as ). The Methylmercury compound has an overall charge of +1, with Hg in the +2 oxidation state. Methylmer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercuric Chloride
Mercury(II) chloride (mercury bichloride, mercury dichloride, mercuric chloride), historically also sulema or corrosive sublimate, is the inorganic chemical compound of mercury and chlorine with the formula HgCl2, used as a laboratory reagent. It is a white crystalline solid and a molecular compound that is very toxic to humans. Once used as a first line treatment for syphilis, it has been replaced by the more effective and less toxic procaine penicillin since at least 1948. Synthesis Mercuric chloride is obtained by the action of chlorine on mercury or on mercury(I) chloride. It can also be produced by the addition of hydrochloric acid to a hot, concentrated solution of mercury(I) compounds such as the nitrate: :Hg2(NO3)2 + 4 HCl → 2 HgCl2 + 2 H2O + 2 NO2 Heating a mixture of solid mercury(II) sulfate and sodium chloride also affords volatile HgCl2, which can be separated by sublimation. Properties Mercuric chloride is not a salt composed of discrete ions, but it is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
