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PH (other)
In chemistry, pH ( ), also referred to as ''acidity'' or ''basicity'', historically denotes "Chemical potential, potential of hydrogen" (or "power of hydrogen"). It is a logarithmic scale used to specify the Acid, acidity or Base (chemistry), basicity of aqueous solutions. Acidic solutions (solutions with higher concentrations of hydrogen (Hydrogen ion#Cation (positively charged), ) Cation, cations) are measured to have lower pH values than basic or alkaline solutions. The pH scale is logarithmic and inversely indicates the Thermodynamic activity, activity of Hydronium, hydrogen cations in the solution : \ce = - \log_(a_\ce) \thickapprox -\log_([\ce]/\text) where [H+] is the Equilibrium chemistry, equilibrium molar concentration of H+ (in M = Mole (unit), mol/Litre, L) in the solution. At 25 Celsius, °C (77 Fahrenheit, °F), solutions of which the pH is less than 7 are acidic, and solutions of which the pH is greater than 7 are basic. Solutions with a pH of 7 at 25&n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Celsius
The degree Celsius is the unit of temperature on the Celsius temperature scale "Celsius temperature scale, also called centigrade temperature scale, scale based on 0 ° for the melting point of water and 100 ° for the boiling point of water at 1 atm pressure." (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the closely related Kelvin scale. The degree Celsius (symbol: °C) can refer to a specific point on the Celsius temperature scale or to a difference or range between two temperatures. It is named after the Swedish astronomer Anders Celsius (1701–1744), who proposed the first version of it in 1742. The unit was called ''centigrade'' in several languages (from the Latin ''centum'', which means 100, and ''gradus'', which means steps) for many years. In 1948, the International Committee for Weights and Measures renamed it to honor Celsius and also to rem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Danish People
Danes (, ), or Danish people, are an ethnic group and nationality native to Denmark and a modern nation identified with the country of Denmark. This connection may be ancestral, legal, historical, or cultural. History Early history Denmark has been inhabited by various Germanic peoples since ancient times, including the Angles (tribe), Angles, Cimbri, Jutes, Herules, Teutones and others. A 2025 study in ''Nature'' found genetic evidence of an influx of central European population after about 500 ce into the region later ruled by the Danes. Viking Age The first mention of Danes within Denmark is on the Jelling stones#Runestone of Harald Bluetooth, Jelling Rune Stone, which mentions the conversion of the Danes to Christianity by Harald Bluetooth in the 10th century. Between and the early 980s, Bluetooth established a kingdom in the lands of the Danes, stretching from Jutland to Scania. Around the same time, he received a visit from a German missionary who, by surviving an t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agronomy
Agronomy is the science and technology of producing and using plants by agriculture for food, fuel, fiber, chemicals, recreation, or land conservation. Agronomy has come to include research of plant genetics, plant physiology, meteorology, and soil science. It is the application of a combination of sciences such as biology, chemistry, economics, ecology, earth science, and genetics. Professionals of agronomy are termed agronomists. Plant breeding This topic of agronomy involves selective breeding of plants to produce the best crops for various conditions. Plant breeding has increased crop yields and has improved the nutritional value of numerous crops, including corn, soybeans, and wheat. It has also resulted in the development of new types of plants. For example, a hybrid grain named triticale was produced by crossbreeding rye and wheat. Triticale contains more usable protein than does either rye or wheat. Agronomy has also been instrumental for fruit and vegetable pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PH Indicator
A pH indicator is a halochromism, halochromic chemical compound added in small amounts to a Solution (chemistry), solution so the pH (acidity or Base (chemistry), basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. Hence, a pH indicator is a Chemical substance, chemical detector for hydronium ions (H3O+) or hydrogen ions (H+) in the Acid-base reaction theories, Arrhenius model. Normally, the indicator causes the color of the solution to change depending on the pH. Indicators can also show change in other physical properties; for example, olfactory indicators show change in their odor. The pH value of a neutral solution is 7.0 at 25°C (Standard conditions for temperature and pressure#Standard laboratory conditions, standard laboratory conditions). Solutions with a pH value below 7.0 are considered acidic and solutions with pH value above 7.0 are basic. Since most naturally occurring Organic compound, organ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PH Meter
A pH meter is a scientific instrument that measures the hydrogen-ion activity in water-based solutions, indicating its acidity or alkalinity expressed as pH. The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode, and so the pH meter is sometimes referred to as a "potentiometric pH meter". The difference in electrical potential relates to the acidity or pH of the solution. Testing of pH via pH meters (pH-metry) is used in many applications ranging from laboratory experimentation to quality control. Applications The rate and outcome of chemical reactions taking place in water often depends on the acidity of the water, and it is therefore useful to know the acidity of the water, typically measured by means of a pH meter. Knowledge of pH is useful or critical in many situations, including chemical laboratory analyses. pH meters are used for soil measurements in agriculture, water quality for municipal water supplies, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glass Electrode
A glass electrode is a type of ion-selective electrode made of a doped glass membrane that is sensitive to a specific ion. The most common application of ion-selective glass electrodes is for the measurement of pH. The pH electrode is an example of a glass electrode that is sensitive to hydrogen ions. Glass electrodes play an important part in the instrumentation for chemical analysis, and physicochemical studies. The voltage of the glass electrode, relative to some reference value, is sensitive to changes in the activity of certain types of ions. History The first studies of glass electrodes (GE) found different sensitivities of different glasses to change the medium's acidity ( pH), due to the effects of the alkali metal ions. In 1906, M. Cremer, the father of Erika Cremer, determined that the electric potential that arises between parts of the fluid, located on opposite sides of the glass membrane, is proportional to the concentration of acid (hydrogen ion concentration). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silver Chloride Electrode
A silver chloride electrode is a type of reference electrode, commonly used in Electrochemistry, electrochemical measurements. For environmental reasons it has widely replaced the saturated calomel electrode. For example, it is usually the internal reference electrode in pH meters and it is often used as reference in reduction potential measurements. As an example of the latter, the silver chloride electrode is the most commonly used reference electrode for testing cathodic protection corrosion control systems in sea water environments. The electrode functions as a reversible redox electrode and the equilibrium is between the solid (s) silver metal (Ag(s)) and its solid salt—silver chloride (AgCl(s), also called silver(I) chloride) in a chloride solution of a given concentration. In electrochemistry, electrochemical cell notation, the silver chloride electrode is written as, ''e.g.'', for an electrolyte solution of KCl 3 M: : \ , \ \ , \ KCl(aq) \ (3M) The corresponding ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Electrode Potential (data Page)
The data below tabulates standard electrode potentials (''E''°), in volts relative to the standard hydrogen electrode (SHE), at: * Temperature ; * Effective concentration (activity) 1 mol/L for each aqueous or amalgamated (mercury-alloyed) species; * Unit activity for each solvent and pure solid or liquid species; and * Absolute partial pressure for each gaseous reagent — the convention in most literature data but not the current standard state (100 kPa). Variations from these ideal conditions affect measured voltage via the Nernst equation. Electrode potentials of successive elementary half-reactions cannot be directly added. However, the corresponding Gibbs free energy changes (∆''G''°) must satisfy :, where electrons are transferred, and the Faraday constant is the conversion factor describing Coulombs transferred per mole electrons. Those Gibbs free energy changes can be added. For example, from , the energy to form one neutral atom of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Electrode
In electrochemistry, the standard hydrogen electrode (abbreviated SHE), is a redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials. Its absolute electrode potential is estimated to be at 25 °C, but to form a basis for comparison with all other electrochemical reactions, hydrogen's standard electrode potential () is declared to be zero volts at any temperature. Potentials of all other electrodes are compared with that of the standard hydrogen electrode at the same temperature. Nernst equation for SHE The hydrogen electrode is based on the redox half cell corresponding to the reduction of two hydrated protons, into one gaseous hydrogen molecule, General equation for a reduction reaction: : \underset + z\ce\ \underset The reaction quotient () of the half-reaction is the ratio between the chemical activities () of the reduced form (the reductant, ) and the oxidized form (the oxidant, ). : Q_r = \frac Considering the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galvanic Cell
A galvanic cell or voltaic cell, named after the scientists Luigi Galvani and Alessandro Volta, respectively, is an electrochemical cell in which an electric current is generated from spontaneous oxidation–reduction reactions. An example of a galvanic cell consists of two different metals, each immersed in separate beakers containing their respective metal ions in solution that are connected by a salt bridge or separated by a porous membrane. Volta was the inventor of the voltaic pile, the first electrical battery. Common usage of the word ''battery'' has evolved to include a single Galvanic cell, but the first batteries had many Galvanic cells. History In 1780, Luigi Galvani discovered that when two different metals (e.g., copper and zinc) are in contact and then both are touched at the same time to two different parts of a muscle of a frog leg, to close the circuit, the frog's leg contracts. He called this " animal electricity". The frog's leg, as well as being a detector ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Measurement Traceability
Traceability is the capability to trace something. In some cases, it is interpreted as the ability to verify the history, location, or application of an item by means of documented recorded identification. Other common definitions include the capability (and implementation) of keeping track of a given set or type of information to a given degree, or the ability to chronologically interrelate uniquely identifiable entities in a way that is verifiable. Traceability is applicable to measurement, supply chain, software development, healthcare and security. Measurement The term ''measurement traceability'' or ''metrological traceability'' is used to refer to an unbroken chain of comparisons relating an instrument's measurements to a known standard. Calibration to a traceable standard can be used to determine an instrument's bias, precision, and accuracy. It may also be used to show a chain of custody—from current interpretation of evidence to the actual evidence in a legal context ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
