EDTA Ethylenediaminetetraacetic
acid,
(HOOCCH 2 ) 2 N(CH 2 ) 2 N(CH 2 COOH) 2 ,
a compound that acts as a chelating
agent, reversibly binding with iron,
magnesium, and other metal ions. It
is used in certain culture media
bound with iron, which it slowly releases into the medium, and also in
some forms of quantitative analysis.
EELS (electron energy loss spectroscopy) A technique for studying
adsorbates and their dissociation. A
beam of electrons is reÛected from a
surface and the energy loss they suffer upon reÛection is measured. This
loss can be used to interpret the vibrational spectrum of the adsorbate.
Very small amounts of adsorbate can
be detected using EELS (as few as 50
atoms in a sample); this is particularly useful for light elements that
are not readily detected using other
techniques.
effervescence The formation of
gas bubbles in a liquid by chemical
reaction.
efÜciency A measure of the performance of a machine, engine, etc.,
being the ratio of the energy or
power it delivers to the energy or
power fed to it. In general, the efÜciency of a machine varies with the
conditions under which it operates
and there is usually a load at which it
operates with the highest efÜciency.
The thermal efÜciency of a heat engine is the ratio of the work done by
the engine to the heat supplied by
the fuel. For a reversible heat engine
this efÜciency equals (T 1 – T 2 )/T 1 ,
where T 1 is the thermodynamic temperature at which all the heat is
taken up and T 2 is the thermodynamic temperature at which it is
given out (see carnot cycle). For real
engines it is always less than this.
efÛorescence The process in
which a crystalline hydrate loses
water, forming a powdery deposit on
the crystals.
effusion The Ûow of a gas through
a small aperture. The relative rates at
which gases effuse, under the same
conditions, is approximately inversely proportional to the square
roots of their densities.
Ehrenfest classiÜcation A
classiÜcation of phase transitions in
terms of their thermodynamic properties put forward by the Dutch
physicist Paul Ehrenfest (1880–1933).
A Ürst-order phase transition is a
phase transition in which the Ürst derivative of the chemical potential is
discontinuous. In a Ürst-order phase
transition there is a nonzero change
in the value of the enthalpy, entropy,
and volume at the transition temperature. Melting and boiling are examples of Ürst-order phase transitions.
In a second-order phase transition,
the Ürst derivative of the chemical
potential is continuous but its second
derivative is not continuous. In a second-order phase transition there is
no jump in the value of the enthalpy,
entropy, and volume at the transition
temperature. Examples of secondorder phase transitions include the
transition to ferromagnetism and
order–disorder transitions in alloys.
Ehrlich’s reagent See p-dimethylaminobenzadehyde.
eigenfunction In general, a solution of an *eigenvalue equation. In
*quantum mechanics eigenfunctions
occur as the allowed wave functions
of a system and so satisfy the
*Schrödinger equation.
eigenvalues The allowed set of values of the constants in an eigenvalue
equation. In an eigenvalue equation
the left-hand side consists of an operator and an *eigenfunction, upon
which the operator operates; the
191
eigenvalues
e
www.AzShimi.ir www.AzShimi.com
acid,
(HOOCCH 2 ) 2 N(CH 2 ) 2 N(CH 2 COOH) 2 ,
a compound that acts as a chelating
agent, reversibly binding with iron,
magnesium, and other metal ions. It
is used in certain culture media
bound with iron, which it slowly releases into the medium, and also in
some forms of quantitative analysis.
EELS (electron energy loss spectroscopy) A technique for studying
adsorbates and their dissociation. A
beam of electrons is reÛected from a
surface and the energy loss they suffer upon reÛection is measured. This
loss can be used to interpret the vibrational spectrum of the adsorbate.
Very small amounts of adsorbate can
be detected using EELS (as few as 50
atoms in a sample); this is particularly useful for light elements that
are not readily detected using other
techniques.
effervescence The formation of
gas bubbles in a liquid by chemical
reaction.
efÜciency A measure of the performance of a machine, engine, etc.,
being the ratio of the energy or
power it delivers to the energy or
power fed to it. In general, the efÜciency of a machine varies with the
conditions under which it operates
and there is usually a load at which it
operates with the highest efÜciency.
The thermal efÜciency of a heat engine is the ratio of the work done by
the engine to the heat supplied by
the fuel. For a reversible heat engine
this efÜciency equals (T 1 – T 2 )/T 1 ,
where T 1 is the thermodynamic temperature at which all the heat is
taken up and T 2 is the thermodynamic temperature at which it is
given out (see carnot cycle). For real
engines it is always less than this.
efÛorescence The process in
which a crystalline hydrate loses
water, forming a powdery deposit on
the crystals.
effusion The Ûow of a gas through
a small aperture. The relative rates at
which gases effuse, under the same
conditions, is approximately inversely proportional to the square
roots of their densities.
Ehrenfest classiÜcation A
classiÜcation of phase transitions in
terms of their thermodynamic properties put forward by the Dutch
physicist Paul Ehrenfest (1880–1933).
A Ürst-order phase transition is a
phase transition in which the Ürst derivative of the chemical potential is
discontinuous. In a Ürst-order phase
transition there is a nonzero change
in the value of the enthalpy, entropy,
and volume at the transition temperature. Melting and boiling are examples of Ürst-order phase transitions.
In a second-order phase transition,
the Ürst derivative of the chemical
potential is continuous but its second
derivative is not continuous. In a second-order phase transition there is
no jump in the value of the enthalpy,
entropy, and volume at the transition
temperature. Examples of secondorder phase transitions include the
transition to ferromagnetism and
order–disorder transitions in alloys.
Ehrlich’s reagent See p-dimethylaminobenzadehyde.
eigenfunction In general, a solution of an *eigenvalue equation. In
*quantum mechanics eigenfunctions
occur as the allowed wave functions
of a system and so satisfy the
*Schrödinger equation.
eigenvalues The allowed set of values of the constants in an eigenvalue
equation. In an eigenvalue equation
the left-hand side consists of an operator and an *eigenfunction, upon
which the operator operates; the
191
eigenvalues
e
www.AzShimi.ir www.AzShimi.com