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ab-initio calculation

ab-initio calculation   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
129 words
A method of calculating atomic and molecular structure directly from the first principles of quantum mechanics, without using quantities derived from experiment (such as ionization ... More
absolute

absolute   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
80 words

1. Not dependent on or relative to anything else, e.g. *absolute zero.

2. Denoting a temperature measured on an ...

absolute configuration

absolute configuration   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
573 words
Illustration(s):
1

A way of denoting the absolute structure of an optical isomer (see optical activity). Two conventions are in use: The ...

absolute zero

absolute zero   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
41 words
Zero of thermodynamic *temperature (0 kelvin) and the lowest temperature theoretically attainable. It is the temperature at which the kinetic energy of atoms and molecules is minimal. It ... More
absorption

absorption   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
116 words

1. (in chemistry) The take up of a gas by a solid or liquid, or the take up of a liquid by a solid. Absorption differs from ...

absorption coefficient

absorption coefficient   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
150 words
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 ... More
absorption tower

absorption tower   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
48 words
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 ... More
ABS plastic

ABS plastic   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
12 words

Any of a class of plastics based on acrylonitrile–butadiene–styrene copolymers.

abstraction

abstraction   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
42 words
Illustration(s):
1

A chemical reaction that involves bimolecular removal of an atom or ion from a molecule. An example is the abstraction of hydrogen from methane by reaction with a radical:...

abundance

abundance   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
102 words
1. The ratio of the total mass of a specified element in the earth’s crust to the total mass of the earth’s crust, often expressed as a percentage. For example, the abundance ... More
ac

ac   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
5 words

Anticlinal. See torsion angle.

acac

acac   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
11 words

The symbol for the *acetylacetonato ligand, used in formulae.

accelerant

accelerant   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
34 words
A flammable material used to start and spread a fire in cases of arson. Petrol and paraffin are the substances commonly used. Traces of accelerant are detectable by gas chromatography in ... More
accelerator

accelerator   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
14 words

A substance that increases the rate of a chemical reaction, i.e. a catalyst.

acceptor

acceptor   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
61 words

1. (in chemistry and biochemistry) A compound, molecule, ion, etc., to which electrons are donated in the formation of a coordinate bond....

accessory pigment

accessory pigment   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
36 words
A *photosynthetic pigment that traps light energy and channels it to chlorophyll a, the primary pigment, which initiates the reactions of photosynthesis. Accessory pigments include the ... More
accumulator

accumulator   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
74 words
A type of *voltaic cell or battery that can be recharged by passing a current through it from an external d.c. supply. The charging current, which is passed in the opposite direction to ... More
acenaphthene

acenaphthene   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
25 words
Illustration(s):
1

A colourless crystalline aromatic compound, C12H10; m.p. 95°C; b.p. 278°C. It is an intermediate in the production of some dyes....

acetals

acetals   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
120 words
Illustration(s):
1

Organic compounds formed by addition of alcohol molecules to aldehyde molecules. If one molecule of aldehyde (RCHO) reacts with one molecule of alcohol (R...

acetanilide

acetanilide   Quick reference

A Dictionary of Chemistry (7 ed.)

Reference type:
Subject Reference
Current Version:
2016
Subject:
Science and technology, Chemistry
Length:
52 words
A white crystalline primary amide of ethanoic acid, CH3CONHC6H5; r.d. 1.2; m.p. 114.3°C; b.p. 304°C. It is made by reacting phenylamine (aniline) with excess ethanoic acid or ethanoic ... More

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