hedral groups T, T h , and T d , the octahedral groups O and O h , and the
icosahedral group I. The SchoenÛies
system is commonly used for isolated
molecules, while the *Hermann–
Mauguin system is commonly used
in crystallography.
schönite A mineral form of potassium sulphate, K 2 SO 4 .
Schottky defect See crystal defect.
Schrödinger, Erwin (1887–1961)
Austrian physicist, who became professor of physics at Berlin University
in 1927. He left for Oxford to escape
the Nazis in 1933, returned to Graz
in Austria in 1936, and then left
again in 1938 for Dublin’s Institute of
Advanced Studies. He Ünally returned
to Austria in 1956. He is best known
for the development of *wave mechanics and the *Schrödinger equation, work that earned him a share of
the 1933 Nobel Prize for physics with
Paul *Dirac.
Schrödinger equation An equation used in wave mechanics (see
quantum mechanics) for the wave
function of a particle. The timeindependent Schrödinger equation is:
∇
2
ψ + 8π
2
m(E – U)ψ/h
2 = 0,
where ψ is the wave function, ∇
2 the
Laplace operator, h the Planck constant, m the particle’s mass, E its total
energy, and U its potential energy. It
can also be written as:
Hψ = Eψ,
where H is the *Hamiltonian operator. It was devised by Erwin
Schrödinger, who was mainly responsible for wave mechanics.
Schweizer’s reagent A solution
made by dissolving copper(II) hydroxide in concentrated ammonia solution. It has a deep blue colour and is
used as a solvent for cellulose in the
cuprammonium process for making
rayon. When the cellulose solution is
forced through spinnarets into an
acid bath, Übres of cellulose are reformed.
Scott’s test (cobalt thiocyanate
test; Ruybal test) A *presumptive
test for cocaine. Scott’s reagent has
an initial solution of 2% cobalt thiocyanate (Co(SCN) 2 ) in glycerine and
water. This is followed by concentrated hydrochloric acid, and then
chloroform. A positive test is indicated by a blue colour in the chloroform layer.
scrubber See absorption tower.
seaborgium Symbol Sg. A radioactive *transactinide element; a.n.
106. It was Ürst detected in 1974 by
Albert Ghiorso and a team in California. It can be produced by bombarding californium-249 nuclei with
oxygen-18 nuclei. It is named after
the US physicist Glenn Seaborg
(1912–99).
A
• Information from the WebElements site
sebacic acid See decanedioic acid.
secondary alcohol See alcohols.
secondary amine See amines.
secondary cell A *voltaic cell in
which the chemical reaction producing the e.m.f. is reversible and the
cell can therefore be charged by passing a current through it. See accumulator; intercalation cell. Compare
primary cell.
secondary emission The emission
of electrons from a surface as a result
of the impact of other charged particles, especially as a result of bombardment with (primary) electrons.
As the number of secondary electrons can exceed the number of primary electrons, the process is
important in photomultipliers. See
also auger effect.
475
secondary emission
s
www.AzShimi.ir www.AzShimi.com
icosahedral group I. The SchoenÛies
system is commonly used for isolated
molecules, while the *Hermann–
Mauguin system is commonly used
in crystallography.
schönite A mineral form of potassium sulphate, K 2 SO 4 .
Schottky defect See crystal defect.
Schrödinger, Erwin (1887–1961)
Austrian physicist, who became professor of physics at Berlin University
in 1927. He left for Oxford to escape
the Nazis in 1933, returned to Graz
in Austria in 1936, and then left
again in 1938 for Dublin’s Institute of
Advanced Studies. He Ünally returned
to Austria in 1956. He is best known
for the development of *wave mechanics and the *Schrödinger equation, work that earned him a share of
the 1933 Nobel Prize for physics with
Paul *Dirac.
Schrödinger equation An equation used in wave mechanics (see
quantum mechanics) for the wave
function of a particle. The timeindependent Schrödinger equation is:
∇
2
ψ + 8π
2
m(E – U)ψ/h
2 = 0,
where ψ is the wave function, ∇
2 the
Laplace operator, h the Planck constant, m the particle’s mass, E its total
energy, and U its potential energy. It
can also be written as:
Hψ = Eψ,
where H is the *Hamiltonian operator. It was devised by Erwin
Schrödinger, who was mainly responsible for wave mechanics.
Schweizer’s reagent A solution
made by dissolving copper(II) hydroxide in concentrated ammonia solution. It has a deep blue colour and is
used as a solvent for cellulose in the
cuprammonium process for making
rayon. When the cellulose solution is
forced through spinnarets into an
acid bath, Übres of cellulose are reformed.
Scott’s test (cobalt thiocyanate
test; Ruybal test) A *presumptive
test for cocaine. Scott’s reagent has
an initial solution of 2% cobalt thiocyanate (Co(SCN) 2 ) in glycerine and
water. This is followed by concentrated hydrochloric acid, and then
chloroform. A positive test is indicated by a blue colour in the chloroform layer.
scrubber See absorption tower.
seaborgium Symbol Sg. A radioactive *transactinide element; a.n.
106. It was Ürst detected in 1974 by
Albert Ghiorso and a team in California. It can be produced by bombarding californium-249 nuclei with
oxygen-18 nuclei. It is named after
the US physicist Glenn Seaborg
(1912–99).
A
• Information from the WebElements site
sebacic acid See decanedioic acid.
secondary alcohol See alcohols.
secondary amine See amines.
secondary cell A *voltaic cell in
which the chemical reaction producing the e.m.f. is reversible and the
cell can therefore be charged by passing a current through it. See accumulator; intercalation cell. Compare
primary cell.
secondary emission The emission
of electrons from a surface as a result
of the impact of other charged particles, especially as a result of bombardment with (primary) electrons.
As the number of secondary electrons can exceed the number of primary electrons, the process is
important in photomultipliers. See
also auger effect.
475
secondary emission
s
www.AzShimi.ir www.AzShimi.com