This can be made by neutralizing
hydrochloric acid with strontium
carbonate, oxide, or hydroxide.
Strontium chloride is used for military Ûares.
strontium hydrogencarbonate
(strontium bicarbonate) A compound, Sr(HCO 3 ) 2 , which is stable
only in solution. It is formed by the
action of carbon dioxide on a suspension of strontium carbonate in water.
On heating, this process is reversed.
strontium oxide (strontia) A white
compound, SrO; r.d. 4.7; m.p. 2430°C,
b.p. 3000°C. It can be prepared by the
decomposition of heated strontium
carbonate, hydroxide, or nitrate, and
is used in the manufacture of other
strontium salts, in pigments, soaps
and greases, and as a drying agent.
strontium sulphate A white solid,
SrSO 4 ; r.d. 3.96; m.p. 1605°C. It can
be made by dissolving strontium
oxide, hydroxide, or carbonate in sulphuric acid. It is used as a pigment in
paints and ceramic glazes and to provide a red colour in Üreworks.
structural formula See formula.
structural isomerism See isomerism.
structure factor A quantity denoted F hkl , where h, k, and l are the
Miller indices of the crystal, which
occurs in *X-ray crystallography and
other experiments involving scattering in crystals. F hkl is deÜned by the
equation:
F hkl = ∑
i
f i exp[2πi(hx i + ky i + lz i )],
where the sum is over all atoms of
the unit cell and f i is the scattering
factor for atom i deÜned by:
f i = 4πΎ 0
∞ (ρsinkr/kr)r
2
dr
Here k = 4πsinθ/λ, where θ is the
Bragg angle (see bragg’s law), λ is the
wavelength of the X-rays, and ρ is the
electron density distribution of the
atom i. The structure factor is used in
Patterson synthesis.
strychnine A colourless poisonous
crystalline alkaloid found in certain
plants.
styrene See phenylethene.
subjacent orbitals The next-tohighest occupied molecular orbital
(NHOMO) and the second-lowest unoccupied molecular orbital (SLUMO).
In certain cases these subjacent orbitals are signiÜcant in *frontierorbital theory.
sublimate A solid formed by sublimation.
sublimation A direct change of
state from solid to gas.
submillimetre waves Electromagnetic radiation with wavelengths
below one millimetre (and therefore
frequencies greater than 300 gigahertz), extending to radiation of the
far infrared. A source of submillimetre radiation is a medium pressure mercury lamp in quartz. Submillimetre waves can be detected by
a *Golay cell.
subshell See atom.
substantive dye See dyes.
substantivity The afÜnity of a dye
for its substrate.
substituent 1. An atom or group
that replaces another in a substitution reaction. 2. An atom or group
regarded as having replaced a hydrogen atom in a chemical derivative.
For example, dibromobenzene
(C 6 H 4 Br 2 ) is a derivative of benzene
with bromine substituents.
substitute natural gas See sng.
substitution reaction (displacement reaction) A reaction in which
one atom or molecule is replaced by
another atom or molecule. See elec507
substitution reaction
s
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hydrochloric acid with strontium
carbonate, oxide, or hydroxide.
Strontium chloride is used for military Ûares.
strontium hydrogencarbonate
(strontium bicarbonate) A compound, Sr(HCO 3 ) 2 , which is stable
only in solution. It is formed by the
action of carbon dioxide on a suspension of strontium carbonate in water.
On heating, this process is reversed.
strontium oxide (strontia) A white
compound, SrO; r.d. 4.7; m.p. 2430°C,
b.p. 3000°C. It can be prepared by the
decomposition of heated strontium
carbonate, hydroxide, or nitrate, and
is used in the manufacture of other
strontium salts, in pigments, soaps
and greases, and as a drying agent.
strontium sulphate A white solid,
SrSO 4 ; r.d. 3.96; m.p. 1605°C. It can
be made by dissolving strontium
oxide, hydroxide, or carbonate in sulphuric acid. It is used as a pigment in
paints and ceramic glazes and to provide a red colour in Üreworks.
structural formula See formula.
structural isomerism See isomerism.
structure factor A quantity denoted F hkl , where h, k, and l are the
Miller indices of the crystal, which
occurs in *X-ray crystallography and
other experiments involving scattering in crystals. F hkl is deÜned by the
equation:
F hkl = ∑
i
f i exp[2πi(hx i + ky i + lz i )],
where the sum is over all atoms of
the unit cell and f i is the scattering
factor for atom i deÜned by:
f i = 4πΎ 0
∞ (ρsinkr/kr)r
2
dr
Here k = 4πsinθ/λ, where θ is the
Bragg angle (see bragg’s law), λ is the
wavelength of the X-rays, and ρ is the
electron density distribution of the
atom i. The structure factor is used in
Patterson synthesis.
strychnine A colourless poisonous
crystalline alkaloid found in certain
plants.
styrene See phenylethene.
subjacent orbitals The next-tohighest occupied molecular orbital
(NHOMO) and the second-lowest unoccupied molecular orbital (SLUMO).
In certain cases these subjacent orbitals are signiÜcant in *frontierorbital theory.
sublimate A solid formed by sublimation.
sublimation A direct change of
state from solid to gas.
submillimetre waves Electromagnetic radiation with wavelengths
below one millimetre (and therefore
frequencies greater than 300 gigahertz), extending to radiation of the
far infrared. A source of submillimetre radiation is a medium pressure mercury lamp in quartz. Submillimetre waves can be detected by
a *Golay cell.
subshell See atom.
substantive dye See dyes.
substantivity The afÜnity of a dye
for its substrate.
substituent 1. An atom or group
that replaces another in a substitution reaction. 2. An atom or group
regarded as having replaced a hydrogen atom in a chemical derivative.
For example, dibromobenzene
(C 6 H 4 Br 2 ) is a derivative of benzene
with bromine substituents.
substitute natural gas See sng.
substitution reaction (displacement reaction) A reaction in which
one atom or molecule is replaced by
another atom or molecule. See elec507
substitution reaction
s
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