hedral groups T, Th, and Td, the octa-
hedral groups O and Oh, 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 potas-
sium sulphate, K 2 SO 4.
Schottky defect See crystal de-
fect.
Schrödinger, Erwin (1887–1961)
Austrian physicist, who became pro-
fessor 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. HeÜnally returned
to Austria in 1956. He is best known
for the development of wave me-
chanics and the Schrödinger equa-
tion, work that earned him a share of
the 1933 Nobel Prize for physics with
Paul *Dirac.
Schrödinger equationAn equa-
tion used in wave mechanics (see
quantum mechanics) for the wave
function of a particle. The time-
independent Schrödinger equation is:
∇^2 ψ+ 8π^2 m(E – U)ψ/h^2 = 0,where ψis the wave function, ∇^2 the
Laplace operator, h the Planck con-
stant, 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 opera-
tor. It was devised by Erwin
Schrödinger, who was mainly re-
sponsible for wave mechanics.
Schweizer’s reagent A solution
made by dissolving copper(II) hydrox-
ide in concentrated ammonia solu-
tion. 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 re-
formed.
Scott’s test (cobalt thiocyanate
test; Ruybal test)A *presumptive
test for cocaine. Scott’s reagent has
an initial solution of 2% cobalt thio-
cyanate (Co(SCN) 2 ) in glycerine and
water. This is followed by concen-
trated hydrochloric acid, and then
chloroform. A positive test is indi-
cated by a blue colour in the chloro-
form layer.scrubberSee absorption tower.
seaborgiumSymbol Sg. A radio-
active *transactinide element; a.n.- It wasÜrst detected in 1974 by
Albert Ghiorso and a team in Califor-
nia. It can be produced by bombard-
ing 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 acidSee decanedioic acid.
secondary alcoholSee alcohols.
secondary amineSee amines.secondary cellA *voltaic cell in
which the chemical reaction produc-
ing the e.m.f. is reversible and the
cell can therefore be charged by pass-
ing a current through it. See accumu-
lator; intercalation cell. Compare
primary cell.secondary emissionThe emission
of electrons from a surface as a result
of the impact of other charged parti-
cles, especially as a result of bom-
bardment with (primary) electrons.
As the number of secondary elec-
trons can exceed the number of pri-
mary electrons, the process is
important in photomultipliers. See
also auger effect.475 secondary emission
s