hydrogen. Sorbitol is used as a sweetener (in diabetic foods) and in the
manufacture of vitamin C and various cosmetics, foodstuffs, and medicines.
sorption *Absorption of a gas by a
solid.
sorption pump A type of vacuum
pump in which gas is removed from
a system by absorption on a solid
(e.g. activated charcoal or a zeolite) at
low temperature.
Soxhlet apparatus An apparatus
for extracting components from a
solid (e.g. extracting natural products
from plant material). The material
used is placed in a thimble made of
thick Ülter paper and this is held in a
specially designed reÛex condenser
with a suitable solvent. The chamber
holding the thimble Ülls with warm
solvent and this is led back to the
source via a side arm. The apparatus
can be operated for long periods,
with components concentrating in
the source vessel. It is named after
Franz Soxhlet, who devised it in
1879.
sp Synperiplanar. See torsion
angle.
space group A group of symmetry
elements applying to a lattice. Compare point group.
species A chemical entity, such as a
particular atom, ion, or molecule.
speciÜc 1. Denoting that an extensive physical quantity so described is
expressed per unit mass. For example, the speciÜc latent heat of a body
is its latent heat per unit mass. When
the extensive physical quantity is denoted by a capital letter (e.g. L for latent heat), the speciÜc quantity is
denoted by the corresponding lowercase letter (e.g. l for speciÜc latent
heat). 2. In some older physical
quantities the adjective ‘speciÜc’ was
added for other reasons (e.g. speciÜc
gravity, speciÜc resistance). These
names are now no longer used.
speciÜc activity See activity.
speciÜc gravity See relative density; specific.
speciÜc heat capacity See heat
capacity.
spectrochemical series A series
of ligands arranged in the order in
which they cause splitting of the energy levels of d-orbitals in metal complexes (see crystal-field theory).
The series for some common ligands
has the form:
CN
–
>NO 2
–
>NH 3 >C 5 H 5 N>H 2 O>OH
–
>
F
–
>Cl
–
>Br
–
>I
–
spectrograph See spectroscope.
spectrometer Any of various instruments for producing a spectrum
and measuring the wavelengths, energies, etc., involved. A simple type,
for visible radiation, is a spectroscope
equipped with a calibrated scale allowing wavelengths to be read off or
calculated. In the X-ray to infrared region of the electromagnetic spectrum, the spectrum is produced by
dispersing the radiation with a prism
or diffraction grating (or crystal, in
the case of hard X-rays). Some form
of photoelectric detector is used, and
the spectrum can be obtained as a
graphical plot, which shows how the
intensity of the radiation varies with
wavelength. Such instruments are
also called spectrophotometers. Spectrometers also exist for investigating
the gamma-ray region and the microwave and radio-wave regions of
the spectrum (see electron paramagnetic resonance; nuclear magnetic resonance). Instruments for
obtaining spectra of particle beams
are also called spectrometers (see
spectrum; photoelectron spectroscopy).
sorption
496
s
www.AzShimi.ir www.AzShimi.com
manufacture of vitamin C and various cosmetics, foodstuffs, and medicines.
sorption *Absorption of a gas by a
solid.
sorption pump A type of vacuum
pump in which gas is removed from
a system by absorption on a solid
(e.g. activated charcoal or a zeolite) at
low temperature.
Soxhlet apparatus An apparatus
for extracting components from a
solid (e.g. extracting natural products
from plant material). The material
used is placed in a thimble made of
thick Ülter paper and this is held in a
specially designed reÛex condenser
with a suitable solvent. The chamber
holding the thimble Ülls with warm
solvent and this is led back to the
source via a side arm. The apparatus
can be operated for long periods,
with components concentrating in
the source vessel. It is named after
Franz Soxhlet, who devised it in
1879.
sp Synperiplanar. See torsion
angle.
space group A group of symmetry
elements applying to a lattice. Compare point group.
species A chemical entity, such as a
particular atom, ion, or molecule.
speciÜc 1. Denoting that an extensive physical quantity so described is
expressed per unit mass. For example, the speciÜc latent heat of a body
is its latent heat per unit mass. When
the extensive physical quantity is denoted by a capital letter (e.g. L for latent heat), the speciÜc quantity is
denoted by the corresponding lowercase letter (e.g. l for speciÜc latent
heat). 2. In some older physical
quantities the adjective ‘speciÜc’ was
added for other reasons (e.g. speciÜc
gravity, speciÜc resistance). These
names are now no longer used.
speciÜc activity See activity.
speciÜc gravity See relative density; specific.
speciÜc heat capacity See heat
capacity.
spectrochemical series A series
of ligands arranged in the order in
which they cause splitting of the energy levels of d-orbitals in metal complexes (see crystal-field theory).
The series for some common ligands
has the form:
CN
–
>NO 2
–
>NH 3 >C 5 H 5 N>H 2 O>OH
–
>
F
–
>Cl
–
>Br
–
>I
–
spectrograph See spectroscope.
spectrometer Any of various instruments for producing a spectrum
and measuring the wavelengths, energies, etc., involved. A simple type,
for visible radiation, is a spectroscope
equipped with a calibrated scale allowing wavelengths to be read off or
calculated. In the X-ray to infrared region of the electromagnetic spectrum, the spectrum is produced by
dispersing the radiation with a prism
or diffraction grating (or crystal, in
the case of hard X-rays). Some form
of photoelectric detector is used, and
the spectrum can be obtained as a
graphical plot, which shows how the
intensity of the radiation varies with
wavelength. Such instruments are
also called spectrophotometers. Spectrometers also exist for investigating
the gamma-ray region and the microwave and radio-wave regions of
the spectrum (see electron paramagnetic resonance; nuclear magnetic resonance). Instruments for
obtaining spectra of particle beams
are also called spectrometers (see
spectrum; photoelectron spectroscopy).
sorption
496
s
www.AzShimi.ir www.AzShimi.com