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Home >> Chemistry Dictionary >>ASS Atomic Absorption Spectroscopy - ABS Plastics
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ASS.
Atomic absorption spectroscopy
Abherents, release agents, parting agents.
Liquid or solid films which reduce or prevent adhesion between surfaces solid-solid, solid-paste, solid-liquid. Waxes, metallic soaps, glycerides, polyvinyl alcohol, silicones, polyethene and fluorocarbons are all used as Abherents in metal, food, rubber, polymer, paper and glass processing abinitor calculations Ouantum mechanical calculations which do not rely upon any experimental data for solution.
Ablation.
Erosion and disintegration due to heat. Ablation resistant materials, particularly Nylon fibres in a phenolic resin, are generally used to protect space vehicles during re-entry into the atmosphere.
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Abrasives.
Hard materials used to disintegrate other materials. Amongst those most widely used are SiC, Al2O3 (often containing Ti), diamond, tungsten carbides, BN, and metal abrasives, e.g. steel wood.
Abrasive.
A substance used for grinding or rubbing down surface e.g. emery.
Absolute (1).
Not dependent on or relative to anything else, e.g. absolute zero (2). Denoting a temperature measured on an absolute scale, a scale of temperature bases on absolute zero. The usual absolute scale now is that of thermodynamics temperature its unit, the Kelvin, was formerly called the degree absolute (A°) and is the same size as the degree Celsius. In British engineering particle an absolute scale with Fahrenheit-size degrees has been used is the Rankine scale.
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Absolute alcohol.
Anhydrous or absolute alcohol obtained by digesting the rectified spirit over quick lime for several days and then redistilling. The first and the last portion are rejected. The main portion of the distillate is 100 percent or absolute alcohol.
Absolute temperature.
A temperature on the ‘absolute’ or Kelvin scale usually denoted by T: the zero of this scale is the temperature at which a perfect gas would occupy zero volume if it could be cooled indefinitely without liquefaction or solidification. The absolute zero (0K) is -273.16°C, and one degree centigrade, T(K) = temperature (°C) + 273.16
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Adaptive landscape
A graph of the average fitness of a population in relation to the frequencies of genotypes in it. Peaks on the landscape correspond to genotypic frequencies at which the average fitness is high, valleys to genotypic frequencies at which the average fitness is low. Also called a fitness surface.
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Absolute zero.
The temperature at which particles would loose all their kineticgy pere.
Absorber.
Refers to an apparatus which is used for the absorption of gases and fort the separation of gas mixtures into the constituent parts by dissolving one or several components in a liquid called absorbent.
Absorptiometer.
An instrument used to measure the absorption of light by a liquid. Also the name of the apparatus used to determine the solubility of a gas in a liquid.
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Absorption.
A process in which gas is taken up by a liquid or solid, or in which is absorbed by another substance is uniformly distributed throughtout the body of the substance. In other words, concentration of the absorbed material will be the same on the surface as well as inside the body.
Absorption indicator.
A type of indicator that is used in reactions that involve precipitation. The yellow dye fluorescein is a common example, used for the reaction.
NaCl(aq) + AgNO3(aq) ----> AgCl(s) + NaNO3(aq)
A silver nitrate solution is added to the sodium chloride, silver chloride precipitates. As for as Cl- ions are in excess, they absorb on the precipitate particles. At the end point, not a single Cl- ions left in solution and negative fluorescein ions are then absorbed, giving a pink colour to the precipitate.
Absorption of gases.
Refers to the taking up (dissolution) of gaseous substances by liquids or solids. Unlike absorption, which is a surface phenomenon, absorption takes place in the bulk of the material that absorbs. It may take place as a mere dissolution but is often accompanied by chemical combination.
Absorption spectroscopy.
A spectroscopic technique qualitative or quantitative, depending upon the measurement of an absorption spectrum.
Abundance.
The ratio of the number of atoms of a particular isotope of an element to the total number of atoms of all the isotopes present, often expressed as a percentage. For example, the abundance of uranium-235 in natural uranium is 0.71%. This is the natural abundance, i.e. the abundance as found in nature before any enrichment has taken place.
ABS plastics.
A group of plastic materials based on blended copolymers of styrene-acrylonitrile (70:30) and butadiene-acrylonitrile (65:35) and on graft interpolymers of styrene and acrylonitrile with Polybutadiene. Used in pipe (25%), appliances (20%), and automotive parts (15%)
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