Simon test A *presumptive test for
methamphetamines. The Simon
reagent consists of 1 gram of sodium
nitroprusside (Na 2 Fe(CN) 5 NO) and 2
ml of acetaldehyde (ethanal) in 50 ml
of water. A 2% solution of sodium
carbonate is then added. MDA gives a
turquoise colour; MDMA gives an initial turquoise, which changes to dark
blue.
SIMS See secondary-ion mass spectrometry.
single bond See chemical bond.
singlet An atomic state in which
two spin angular momenta of electrons cancel each other, resulting in
zero net spin. A singlet state usually
has a higher energy than a *triplet
state because of the effect of correlations of spin on the Coulomb interactions between electrons (as in
*Hund’s rules). This can lead to substantial energy differences between
triplet and singlet states.
sintered glass Porous glass made
by sintering powdered glass, used for
Ültration of precipitates in gravimetric analysis.
sintering The process of heating
and compacting a powdered material
at a temperature below its melting
point in order to weld the particles
together into a single rigid shape.
Materials commonly sintered include
metals and alloys, glass, and ceramic
oxides. Sintered magnetic materials,
cooled in a magnetic Üeld, make especially retentive permanent magnets.
S-isomer See absolute configuration.
SI units Système International
d’Unités: the international system of
units now recommended for all scientiÜc purposes. A coherent and rationalized system of units derived
from the *m.k.s. units, SI units have
now replaced *c.g.s. units and *Imperial units. The system has seven base
units and two dimensionless units
(formerly called supplementary
units), all other units being derived
from these nine units. There are 18
derived units with special names.
Each unit has an agreed symbol (a
capital letter or an initial capital letter if it is named after a scientist,
otherwise the symbol consists of one
or two lower-case letters). Decimal
multiples of the units are indicated
by a set of preÜxes; whenever possible a preÜx representing 10 raised to
a power that is a multiple of three
should be used. See Appendix.
skeletal electrons See wade’s
rules.
skew See torsion angle.
slag Material produced during the
*smelting or reÜning of metals by reaction of the Ûux with impurities
(e.g. calcium silicate formed by reaction of calcium oxide Ûux with silicon dioxide impurities). The liquid
slag can be separated from the liquid
metal because it Ûoats on the surface.
See also basic slag.
slaked lime See calcium hydroxide.
SLN See sybyl line notation.
SLUMO Second-lowest unoccupied
molecular orbital. See subjacent orbitals.
slurry A paste consisting of a suspension of a solid in a liquid.
SMARTS See smiles.
smectic See liquid crystal.
smelting The process of separating
a metal from its ore by heating the
ore to a high temperature in a suitable furnace in the presence of a reducing agent, such as carbon, and a
Ûuxing agent, such as limestone. Iron
485
smelting
s
www.AzShimi.ir www.AzShimi.com
methamphetamines. The Simon
reagent consists of 1 gram of sodium
nitroprusside (Na 2 Fe(CN) 5 NO) and 2
ml of acetaldehyde (ethanal) in 50 ml
of water. A 2% solution of sodium
carbonate is then added. MDA gives a
turquoise colour; MDMA gives an initial turquoise, which changes to dark
blue.
SIMS See secondary-ion mass spectrometry.
single bond See chemical bond.
singlet An atomic state in which
two spin angular momenta of electrons cancel each other, resulting in
zero net spin. A singlet state usually
has a higher energy than a *triplet
state because of the effect of correlations of spin on the Coulomb interactions between electrons (as in
*Hund’s rules). This can lead to substantial energy differences between
triplet and singlet states.
sintered glass Porous glass made
by sintering powdered glass, used for
Ültration of precipitates in gravimetric analysis.
sintering The process of heating
and compacting a powdered material
at a temperature below its melting
point in order to weld the particles
together into a single rigid shape.
Materials commonly sintered include
metals and alloys, glass, and ceramic
oxides. Sintered magnetic materials,
cooled in a magnetic Üeld, make especially retentive permanent magnets.
S-isomer See absolute configuration.
SI units Système International
d’Unités: the international system of
units now recommended for all scientiÜc purposes. A coherent and rationalized system of units derived
from the *m.k.s. units, SI units have
now replaced *c.g.s. units and *Imperial units. The system has seven base
units and two dimensionless units
(formerly called supplementary
units), all other units being derived
from these nine units. There are 18
derived units with special names.
Each unit has an agreed symbol (a
capital letter or an initial capital letter if it is named after a scientist,
otherwise the symbol consists of one
or two lower-case letters). Decimal
multiples of the units are indicated
by a set of preÜxes; whenever possible a preÜx representing 10 raised to
a power that is a multiple of three
should be used. See Appendix.
skeletal electrons See wade’s
rules.
skew See torsion angle.
slag Material produced during the
*smelting or reÜning of metals by reaction of the Ûux with impurities
(e.g. calcium silicate formed by reaction of calcium oxide Ûux with silicon dioxide impurities). The liquid
slag can be separated from the liquid
metal because it Ûoats on the surface.
See also basic slag.
slaked lime See calcium hydroxide.
SLN See sybyl line notation.
SLUMO Second-lowest unoccupied
molecular orbital. See subjacent orbitals.
slurry A paste consisting of a suspension of a solid in a liquid.
SMARTS See smiles.
smectic See liquid crystal.
smelting The process of separating
a metal from its ore by heating the
ore to a high temperature in a suitable furnace in the presence of a reducing agent, such as carbon, and a
Ûuxing agent, such as limestone. Iron
485
smelting
s
www.AzShimi.ir www.AzShimi.com