الرئيسية » Simplified Chemistry (صفحه 22)

Simplified Chemistry

activation analysis

An analytical technique that can be used to detect most elements when present in a sample in milligram quantities (or less). In neutron activation analysis the sample is exposed to a flux of thermal neutrons in a nuclear reac­tor. Some of these neutrons are cap­tured by nuclides in the sample …

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activated sludge process

A sewage and waste-water treatment. The sludge produced after primary treatment is pumped into aeration tanks, where it is continuously stirred and aerated, resulting in the formation of small aggregates of sus­pended colloidal organic matter called floe. Floe contains numerous slime-forming and nitrifying bac­teria, as well as protozoans, which decompose …

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absorption tower

A long vertical column used in industry for absorbing gases. The gas is introduced at the bottom of the column and the absorbing liquid, often water, passes in at the top and falls down against the countercurrent of gas. The towers are also known as scrubbers.

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absorption coefficient

1. (in spectroscopy) The molar absorption coefficient (symbol ε ) is a quantity that characterizes the absorption of light (or any other type of electromagnetic radiation) as it passes through a sample of the absorbing material. It has the dimensions of 1/{concentration x length). e is de­pendent on the frequency …

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absolute configuration

A way of denoting the absolute structure of an optical isomer . Two conventions are in use: The D-L convention relates the structure of the molecule to some reference molecule. In the case of sugars and similar compounds, the dextrorotatory form of glyceraldehyde (HOCH2CH(OH)CHO , 2,3-dihydroxy­propanal) was used. The rule …

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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 based on absolute zero. The usual absolute scale now is that of thermodynamic temperature; its unit, the kelvin, was formerly called the degree absolute (0A) …

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