cellulose acetate is made and dissolved in a solvent. The solution is
forced through nozzles into air,
where the solvent quickly evaporates
leaving a Ülament of acetate rayon.
RBS See rutherford backscattering spectrometry.
RDX See cyclonite.
reactant See chemical reaction.
reaction See chemical reaction.
reactive dye See dyes.
reagent A substance reacting with
another substance. Laboratory
reagents are compounds, such as sulphuric acid, hydrochloric acid,
sodium hydroxide, etc., used in
chemical analysis or experiments.
realgar A red mineral form of arsenic(II) sulphide, As 2 S 2 .
real gas A gas that does not have
the properties assigned to an *ideal
gas. Its molecules have a Ünite size
and there are forces between them
(see equation of state).
rearrangement A type of chemical
reaction in which the atoms in a
molecule rearrange to form a new
molecule. Examples are the *pinacol
rearrangement and the *Wagner–
Meerwein rearrangement.
reciprocal lattice A lattice for a
crystal that can be deÜned from the
lattice in real space. If the primitive
translation vectors of the lattice in
real space are denoted by a, b, c then
the primitive translations a′, b′, c′ in
the reciprocal lattice are deÜned by
a′ = b × c[abc], b′ = c × a[abc], c′ =
a × b[abc], where [abc] denotes the
scalar triple product a.(b × c).
The reciprocal lattice is a fundamental concept in the theory of *Xray diffraction and energy bands
with a diffraction pattern being
much more closely related to the reciprocal lattice than the real-space lattice.
reciprocal proportions See chemical combination.
recombination process The
process in which a neutral atom or
molecule is formed by the combination of a positive ion and a negative
ion or electron; i.e. a process of the
type:
A
+ + B
–
→ AB
or
A
+ + e
–
→ A
In recombination, the neutral
species formed is usually in an excited state, from which it can decay
with emission of light or other electromagnetic radiation.
recreational drug A drug used for
recreation, as opposed to medical
use. Strictly, recreational drugs include alcohol and nicotine, but the
term is often understood to mean
substances such as marijuana, cocaine, and amphetamines.
recrystallization A process of repeated crystallization in order to purify a substance or to obtain more
regular crystals of a puriÜed substance.
rectiÜcation The process of purifying a liquid by *distillation. See fractional distillation.
rectiÜed spirit A constant-boiling
mixture of *ethanol (95.6°) and
water; it is obtained by distillation.
red lead See dilead(ii) lead(iv)
oxide.
redox See oxidation–reduction.
reducing agent (reductant) A substance that brings about reduction in
other substances. It achieves this by
being itself oxidized. Reducing
agents contain atoms with low oxidation numbers; that is the atoms have
RBS
456
r
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forced through nozzles into air,
where the solvent quickly evaporates
leaving a Ülament of acetate rayon.
RBS See rutherford backscattering spectrometry.
RDX See cyclonite.
reactant See chemical reaction.
reaction See chemical reaction.
reactive dye See dyes.
reagent A substance reacting with
another substance. Laboratory
reagents are compounds, such as sulphuric acid, hydrochloric acid,
sodium hydroxide, etc., used in
chemical analysis or experiments.
realgar A red mineral form of arsenic(II) sulphide, As 2 S 2 .
real gas A gas that does not have
the properties assigned to an *ideal
gas. Its molecules have a Ünite size
and there are forces between them
(see equation of state).
rearrangement A type of chemical
reaction in which the atoms in a
molecule rearrange to form a new
molecule. Examples are the *pinacol
rearrangement and the *Wagner–
Meerwein rearrangement.
reciprocal lattice A lattice for a
crystal that can be deÜned from the
lattice in real space. If the primitive
translation vectors of the lattice in
real space are denoted by a, b, c then
the primitive translations a′, b′, c′ in
the reciprocal lattice are deÜned by
a′ = b × c[abc], b′ = c × a[abc], c′ =
a × b[abc], where [abc] denotes the
scalar triple product a.(b × c).
The reciprocal lattice is a fundamental concept in the theory of *Xray diffraction and energy bands
with a diffraction pattern being
much more closely related to the reciprocal lattice than the real-space lattice.
reciprocal proportions See chemical combination.
recombination process The
process in which a neutral atom or
molecule is formed by the combination of a positive ion and a negative
ion or electron; i.e. a process of the
type:
A
+ + B
–
→ AB
or
A
+ + e
–
→ A
In recombination, the neutral
species formed is usually in an excited state, from which it can decay
with emission of light or other electromagnetic radiation.
recreational drug A drug used for
recreation, as opposed to medical
use. Strictly, recreational drugs include alcohol and nicotine, but the
term is often understood to mean
substances such as marijuana, cocaine, and amphetamines.
recrystallization A process of repeated crystallization in order to purify a substance or to obtain more
regular crystals of a puriÜed substance.
rectiÜcation The process of purifying a liquid by *distillation. See fractional distillation.
rectiÜed spirit A constant-boiling
mixture of *ethanol (95.6°) and
water; it is obtained by distillation.
red lead See dilead(ii) lead(iv)
oxide.
redox See oxidation–reduction.
reducing agent (reductant) A substance that brings about reduction in
other substances. It achieves this by
being itself oxidized. Reducing
agents contain atoms with low oxidation numbers; that is the atoms have
RBS
456
r
www.AzShimi.ir www.AzShimi.com