Silver nitrate is an inorganic compound with chemical formula AgNO3. This compound is a precursor to many other silver compounds. It is far less sensitive to light than the halides and it was once called lunar caustic because silver was called luna by the ancient alchemists, who believed that silver was associated with the moon. In solid silver nitrate, the ions are three-coordinated in a trigonal planar arrangement. Albertus Magnus, in the 13th century, documented the ability of nitric acid to separate gold, Magnus noted that the resulting solution of silver nitrate could blacken skin. Silver nitrate can be prepared by reacting silver, such as a silver bullion or silver foil, with acid, resulting in silver nitrate, water. Reaction byproducts depend upon the concentration of acid used. 3 Ag +4 HNO3 →3 AgNO3 +2 H2O + NO Ag +2 HNO3 → AgNO3 + H2O + NO2 This is performed under a fume hood because of nitrogen oxide evolved during the reaction. A typical reaction with silver nitrate is to suspend a rod of copper in a solution of silver nitrate, silver nitrate is the least expensive salt of silver, it offers several other advantages as well.
It is non-hygroscopic, in contrast to silver fluoroborate and silver perchlorate and it is relatively stable to light. Finally, it dissolves in solvents, including water. The nitrate can be replaced by other ligands, rendering AgNO3 versatile. Treatment with solutions of halide ions gives a precipitate of AgX, silver nitrate is used to prepare some silver-based explosives, such as the fulminate, azide, or acetylide, through a precipitation reaction. This reaction is used in inorganic chemistry to abstract halides, Ag+ + X− → AgX where X− = Cl−, Br−. Other silver salts with non-coordinating anions, namely silver tetrafluoroborate and silver hexafluorophosphate are used for demanding applications. Similarly, this reaction is used in chemistry to confirm the presence of chloride, bromide. Samples are typically acidified with nitric acid to remove interfering ions, e. g. carbonate ions. This step avoids confusion of silver sulfide or silver carbonate precipitates with that of silver halides, the color of precipitate varies with the halide, pale yellow/cream, yellow
Nucleation is the first step in the formation of either a new thermodynamic phase or a new structure via self-assembly or self-organization. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears, nucleation is often found to be very sensitive to impurities in the system. Because of this, it is important to distinguish between heterogeneous nucleation and homogeneous nucleation. Heterogeneous nucleation occurs at sites on surfaces in the system. Homogeneous nucleation occurs away from a surface, nucleation is usually a stochastic process, so even in two identical systems nucleation will occur at different times. This behaviour is similar to radioactive decay, a common mechanism is illustrated in the animation to the right. This shows nucleation of a new phase in an existing phase and this nucleus of the red phase grows and converts the system to this phase. The standard theory that describes this behaviour for the nucleation of a new phase is called classical nucleation theory.
This is seen for example in the nucleation of ice in supercooled water droplets. The decay rate of the exponential gives the nucleation rate, classical nucleation theory is a widely used approximate theory for estimating these rates, and how they vary with variables such as temperature. It correctly predicts that the time you have to wait for nucleation decreases extremely rapidly when supersaturated and it is not just new phases such as liquids and crystals that form via nucleation followed by growth. The self-assembly process that forms objects like the amyloid aggregates associated with Alzheimers disease starts with nucleation, energy consuming self-organising systems such as the microtubules in cells show nucleation and growth. Clouds form when wet air cools and many small water droplets nucleate from the supersaturated air, the amount of water vapor that air can carry decreases with lower temperatures. The excess vapor begins to nucleate and to small water droplets which form a cloud.
Nucleation of the droplets of water is heterogeneous, occurring on particles referred to as cloud condensation nuclei. Cloud seeding is the process of adding artificial condensation nuclei to quicken the formation of clouds, nucleation is the first step in crystallisation, so it determines if a crystal can form. Frequently crystals do not form even when they are thermodynamically the favored state, for example, small droplets of very pure water can remain liquid down to below -30 °C although ice is the stable state below 0 °C. Bubbles of carbon dioxide nucleate shortly after the pressure is released from a container of carbonated liquid, nucleation often occurs more easily at a pre-existing interface, as happens on boiling chips and on string used to make rock candy
The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium, the melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the change from liquid to solid. Because of the ability of some substances to supercool, the point is not considered as a characteristic property of a substance. For most substances and freezing points are approximately equal, for example, the melting point and freezing point of mercury is 234.32 kelvins. However, certain substances possess differing solid-liquid transition temperatures, for example, agar melts at 85 °C and solidifies from 31 °C to 40 °C, such direction dependence is known as hysteresis. The melting point of ice at 1 atmosphere of pressure is close to 0 °C. In the presence of nucleating substances the freezing point of water is the same as the melting point, the chemical element with the highest melting point is tungsten, at 3687 K, this property makes tungsten excellent for use as filaments in light bulbs.
Many laboratory techniques exist for the determination of melting points, a Kofler bench is a metal strip with a temperature gradient. Any substance can be placed on a section of the strip revealing its thermal behaviour at the temperature at that point, differential scanning calorimetry gives information on melting point together with its enthalpy of fusion. A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window, the several grains of a solid are placed in a thin glass tube and partially immersed in the oil bath. The oil bath is heated and with the aid of the melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, the measurement can be made continuously with an operating process. For instance, oil refineries measure the point of diesel fuel online, meaning that the sample is taken from the process. This allows for more frequent measurements as the sample does not have to be manually collected, for refractory materials the extremely high melting point may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer.
For the highest melting materials, this may require extrapolation by several hundred degrees, the spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source that has been previously calibrated as a function of temperature, in this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer, for temperatures above the calibration range of the source, an extrapolation technique must be employed
Antiseptic are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. Disinfectants do not kill bacterial spores e. g. on surgical instruments, even sterilization may not destroy prions. Some antibiotics are true germicides, capable of destroying microbes, while others are bacteriostatic, antibacterials are antiseptics that have the proven ability to act against bacteria. Microbicides which destroy virus particles are called viricides or antivirals, antisepsis was recommended by Hungarian physician Ignaz Semmelweis in 1847 but, tragically, he was ignored. In this paper, Lister advocated the use of acid as a method of ensuring that any germs present were killed. Some of this work was anticipated by, Ancient Greek physicians Galen and Hippocrates and their theories were bitterly opposed by Galenist Guy de Chauliac and others trained in the classical tradition. Joseph Smith alluded to the use of alcohol as an antiseptic in February 1833, verse 7 states, again, strong drinks are not for the belly, but for the washing of your bodies.
More commonly, 3% solutions of hydrogen peroxide have been used in household first aid for scrapes, the strong oxidization causes scar formation and increases healing time during fetal development. Iodine is usually used in a solution or as Lugols iodine solution as a pre-. Some people do not recommend disinfecting minor wounds with iodine because of concern that it may induce scar tissue formation, concentrations of 1% iodine or less have not been shown to increase healing time and are not otherwise distinguishable from treatment with saline. Polyhexanide is a compound suitable for clinical use in critically colonized or infected acute. The physicochemical action on the bacterial envelope prevents or impedes the development of resistant bacterial strains, balsam of Peru is a mild antiseptic. By continued exposure to antibiotics, bacteria may evolve to the point where they are no longer harmed by these compounds, bacteria can develop a resistance to antiseptics, but the effect is generally less pronounced.
The mechanism by which bacteria evolve may vary in response to different antiseptics, low concentrations of an antiseptic may encourage growth of a bacterial strain that is resistant to the antiseptic, where a higher concentration of the antiseptic would simply kill the bacteria. In addition, use of a high concentration of an antiseptic may cause tissue damage or slow the process of wound healing
The usual intent is to increase precipitation, but hail and fog suppression are widely practiced in airports. Cloud seeding occurs due to ice nucleators in nature, most of which are bacterial in origin, the most common chemicals used for cloud seeding include silver iodide, potassium iodide and dry ice. Liquid propane, which expands into a gas, has been used and this can produce ice crystals at higher temperatures than silver iodide. After promising research, the use of materials, such as table salt, is becoming more popular. When Cloud seeding increases snowfall takes place when temperatures within the clouds are between 19 and −4 °F, introduction of a substance such as silver iodide, which has a crystalline structure similar to that of ice, will induce freezing nucleation. In mid-latitude clouds, the usual seeding strategy has been based on the fact that the vapor pressure is lower over ice than over water. The formation of ice particles in super cooled clouds allows those particles to grow at the expense of liquid droplets, if sufficient growth takes place, the particles become heavy enough to fall as precipitation from clouds that otherwise would produce no precipitation.
This process is known as static seeding, Seeding of warm-season or tropical cumulonimbus clouds seeks to exploit the latent heat released by freezing. Cloud seeding chemicals may be dispersed by aircraft or by dispersion devices located on the ground, for release by aircraft, silver iodide flares are ignited and dispersed as an aircraft flies through the inflow of a cloud. When released by devices on the ground, the particles are carried downwind. An electronic mechanism was tested in 2010, when infrared laser pulses were directed to the air above Berlin by researchers from the University of Geneva, the experimenters posited that the pulses would encourage atmospheric sulfur dioxide and nitrogen dioxide to form particles that would act as seeds. Cloud seeding has never been proven to work. Claims are made that new technology and research has produced results that make cloud seeding a dependable and affordable water supply practice for many regions. But while practiced widely around the world, the effectiveness of cloud seeding is still a matter of academic debate, in 2003 the US National Research Council released a report stating. science is unable to say with assurance which, if any, seeding techniques produce positive effects.
In the 55 years following the first cloud-seeding demonstrations, substantial progress has made in understanding the natural processes that account for our daily weather. Yet scientifically acceptable proof for significant seeding effects has not been achieved, referring to 1903,1915,1919,1944, and 1947 weather modification experiments, the Australian Federation of Meteorology discounted rain making. By the 1950s, the CSIRO Division of Radiophysics switched to investigating the physics of clouds and had hoped by 1957 to better understand these processes. By the 1960s, the dreams of making had faded only to be re-ignited post-corporatisation of the Snowy Mountains Scheme in order to achieve above target water
The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the environmental pressure. A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a boiling point than when that liquid is at atmospheric pressure. For a given pressure, different liquids boil at different temperatures, for example, water boils at 100 °C at sea level, but at 93.4 °C at 2,000 metres altitude. The normal boiling point of a liquid is the case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level,1 atmosphere. At that temperature, the pressure of the liquid becomes sufficient to overcome atmospheric pressure. The standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of 1 bar, the heat of vaporization is the energy required to transform a given quantity of a substance from a liquid into a gas at a given pressure.
Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation, evaporation is a surface phenomenon in which molecules located near the liquids edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, a saturated liquid contains as much thermal energy as it can without boiling. The saturation temperature is the temperature for a corresponding saturation pressure at which a liquid boils into its vapor phase, the liquid can be said to be saturated with thermal energy. Any addition of energy results in a phase transition. If the pressure in a system remains constant, a vapor at saturation temperature will begin to condense into its liquid phase as thermal energy is removed, similarly, a liquid at saturation temperature and pressure will boil into its vapor phase as additional thermal energy is applied. The boiling point corresponds to the temperature at which the pressure of the liquid equals the surrounding environmental pressure.
Thus, the point is dependent on the pressure. Boiling points may be published with respect to the NIST, USA standard pressure of 101.325 kPa, at higher elevations, where the atmospheric pressure is much lower, the boiling point is lower. The boiling point increases with increased pressure up to the critical point, the boiling point cannot be increased beyond the critical point. Likewise, the point decreases with decreasing pressure until the triple point is reached
Precipitation is the creation of a solid from a solution. When the reaction occurs in a 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 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, 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 historically been known as flowers. When the solid appears in the form of fibers which have been through chemical processing. Sometimes the formation of a precipitate indicates the occurrence of a chemical reaction, if silver nitrate solution is poured into a solution of sodium chloride, a chemical reaction occurs forming a white precipitate of silver chloride. When potassium iodide solution reacts with lead nitrate solution, a precipitate of lead iodide is formed.
Precipitation may occur if the concentration of a compound exceeds its solubility, Precipitation may occur rapidly from a supersaturated solution. Precipitation in solids is routinely used to synthesize nanoclusters, an important stage of the precipitation process is the onset of nucleation. The creation of a solid particle includes the formation of an interface, which requires some energy based on the relative surface energy of the solid. If this energy is not available, and no suitable nucleation surface is available, Precipitation reactions can be used for making pigments, removing salts from water in water treatment, and in classical qualitative inorganic analysis. Precipitation is useful to isolate the products of a reaction during workup, the product of the reaction is insoluble in the reaction solvent. Thus, it precipitates as it is formed, preferably forming pure crystals, an example of this would be the synthesis of porphyrins in refluxing propionic acid. Thereafter, the precipitate may easily be separated by filtration, decanting, an example would be the synthesis of chromic tetraphenylporphyrin chloride, water is added to the DMF reaction solution, and the product precipitates.
Precipitation is useful in purifying products, crude bmim-Cl is taken up in acetonitrile, and dropped into ethyl acetate, another important application of an antisolvent is in ethanol precipitation of DNA. In metallurgy, precipitation from a solution is a useful way to strengthen alloys. An example of a reaction, Aqueous silver nitrate is added to a solution containing potassium chloride
Silver is a metallic element with symbol Ag and atomic number 47. The symbol Ag stems from Latin argentum, derived from the Greek ὰργὀς, a soft, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal is found in the Earths crust in the pure, free form, as an alloy with gold and other metals. Most silver is produced as a byproduct of copper, lead, Silver is more abundant than gold, but it is much less abundant as a native metal. Its purity is measured on a per mille basis, a 94%-pure alloy is described as 0.940 fine. As one of the seven metals of antiquity, silver has had a role in most human cultures. Silver has long valued as a precious metal. Silver metal is used in many premodern monetary systems in bullion coins, Silver is used in numerous applications other than currency, such as solar panels, water filtration, ornaments, high-value tableware and utensils, and as an investment medium. Silver is used industrially in electrical contacts and conductors, in specialized mirrors, window coatings, Silver compounds are used in photographic film and X-rays.
Dilute silver nitrate solutions and other compounds are used as disinfectants and microbiocides, added to bandages and wound-dressings, catheters. Silver is similar in its physical and chemical properties to its two neighbours in group 11 of the periodic table and gold. This distinctive electron configuration, with an electron in the highest occupied s subshell over a filled d subshell. Silver is a soft and malleable transition metal. Silver crystallizes in a cubic lattice with bulk coordination number 12. Unlike metals with incomplete d-shells, metallic bonds in silver are lacking a covalent character and are relatively weak and this observation explains the low hardness and high ductility of single crystals of silver. Silver has a brilliant white metallic luster that can take a polish. Protected silver has greater optical reflectivity than aluminium at all wavelengths longer than ~450 nm, at wavelengths shorter than 450 nm, silvers reflectivity is inferior to that of aluminium and drops to zero near 310 nm.
The electrical conductivity of silver is the greatest of all metals, greater even than copper, during World War II in the US,13540 tons of silver were used in electromagnets for enriching uranium, mainly because of the wartime shortage of copper
The Cessna 210 Centurion is a six-seat, high-performance, retractable-gear, single-engine, high-wing general aviation aircraft which was first flown in January 1957 and produced by Cessna until 1985. The early Cessna 210 had four seats with a Continental IO-470 engine of 260 hp and it was essentially a Cessna 182B to which was added a retractable landing gear, swept tail, and a new wing. In 1961 the fuselage and wing were completely redesigned - the fuselage was made wider and deeper, the wing planform remained the same, but the semi-Fowler flaps were extended outboard, from Wing Station 100 to Wing Station 122, which allowed a lower landing speed. To compensate for the reduced aileron span, the profile was changed. The 1964 model 210D introduced a 285 hp engine and two child seats, set into the cavity which contained the mainwheels aft of the passengers. In 1967 the model 210G introduced a cantilever wing replacing the strut-braced wing and its planform changed to a constant taper from root chord to tip chord.
In 1970 the 210K became the first full six-seat model and this was achieved by replacing the flat leaf-springs used for the retractable main landing gear struts with tapered tubular steel struts of greater length. This allowed the tires to be nested farther to the rear of the fuselage, in 1979 the 210N model eliminated the folding doors which previously covered the two retracted main wheels. The tubular spring struts retract into shallow channels along the bottom of the fuselage, some models featured de-icing boots as an option. The aircraft was offered in a normally aspirated version, designated the model 210, as well as the turbocharged T210, Aircraft with more than 10,000 hours of airframe time were grounded immediately pending a visual inspection. In November 2007, Cessna acquired the assets of Columbia Aircraft Company, the Columbia 350 and 400 models were integrated into the Cessna single-engined range and redesignated as the Cessna 350 and Cessna 400. These aircraft replaced the Cessna 210 at the top end of the Cessna single-engined model line, crownair Aviation developed a “Centurion Edition” T210, which is a remanufactured aircraft introduced in November 2008 that features a glass cockpit and new engine along with other minor refinements.
O&N Aircraft offers a Rolls-Royce Model 250 turboprop conversion of the T210, riley Rocket - Restoration and addition of intercooler to Continental TSIO-520 models to boost from 310 to 340 hp. Vitatoe Aviation offers the TN550 conversion which uses a Continental IO-550P engine with an IO-520 turbocharger with dual intercoolers, the Cessna 210 was manufactured in 26 model variants. The C210, C210A-D, the Centurion C210E-H&J, Turbo Centurion T210F-H&J, the Centurion II C210K-N&R, the Turbo Centurion II T210K-N&R, the 210N, T210N, and P210N versions were produced in the greatest quantity. The rarest and most expensive models were the T210R and P210R, several modifications and optional fittings are available including different engine installations, wingtip tanks, speed brakes, STOL kits and gear door modifications. The early strut-winged Cessna 210B was developed into an aircraft known as the Cessna 205. This spawned a new family of Cessna aircraft including the 206
The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume.
In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume.
As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter. The smallest group of particles in the material that constitutes the pattern is the unit cell of the structure. The unit cell completely defines the symmetry and structure of the crystal lattice. The repeating patterns are said to be located at the points of the Bravais lattice, the lengths of the principal axes, or edges, of the unit cell and the angles between them are the lattice constants, called lattice parameters. The symmetry properties of the crystal are described by the concept of space groups, all possible symmetric arrangements of particles in three-dimensional space may be described by the 230 space groups. The crystal structure and symmetry play a role in determining many physical properties, such as cleavage, electronic band structure.
The crystal structure of a material can be described in terms of its unit cell, the unit cell is a box containing one or more atoms arranged in three dimensions. The unit cells stacked in three-dimensional space describe the arrangement of atoms of the crystal. Commonly, atomic positions are represented in terms of fractional coordinates, the atom positions within the unit cell can be calculated through application of symmetry operations to the asymmetric unit. The asymmetric unit refers to the smallest possible occupation of space within the unit cell and this does not, however imply that the entirety of the asymmetric unit must lie within the boundaries of the unit cell. Symmetric transformations of atom positions are calculated from the group of the crystal structure. Vectors and planes in a lattice are described by the three-value Miller index notation. It uses the indices ℓ, m, and n as directional parameters, which are separated by 90°, by definition, the syntax denotes a plane that intercepts the three points a1/ℓ, a2/m, and a3/n, or some multiple thereof.
That is, the Miller indices are proportional to the inverses of the intercepts of the plane with the unit cell, if one or more of the indices is zero, it means that the planes do not intersect that axis. A plane containing a coordinate axis is translated so that it no longer contains that axis before its Miller indices are determined, the Miller indices for a plane are integers with no common factors. Negative indices are indicated with horizontal bars, as in, in an orthogonal coordinate system for a cubic cell, the Miller indices of a plane are the Cartesian components of a vector normal to the plane. Likewise, the planes are geometric planes linking nodes