diethanolamine See ethanolamine.
diethyl ether See ethoxyethane.
differential scanning calorimetry (DSC) See thermal analysis.
differential thermal analysis
(DTA) See thermal analysis.
diffusion 1. The process by which
different substances mix as a result
of the random motions of their component atoms, molecules, and ions.
In gases, all the components are perfectly miscible with each other and
mixing ultimately becomes nearly
uniform, though slightly affected by
gravity (see also graham’s law). The
diffusion of a solute through a solvent to produce a solution of uniform concentration is slower, but
otherwise very similar to the process
of gaseous diffusion. In solids, diffusion occurs very slowly at normal
temperatures. See also fick’s law.
2. The passage of elementary particles through matter when there is a
high probability of scattering and a
low probability of capture.
diffusion constant See fick’s law.
diffusion gradient See concentration gradient.
diffusion limited aggregation
(DLA) A process of aggregation dominated by particles diffusing and having a nonzero probability of sticking
together irreversibly when they
touch. The clusters formed by DLA
are *fractal in type.
diffusion pump (condensation
pump) A vacuum pump in which oil
or mercury vapour is diffused
through a jet, which entrains the gas
molecules from the container in
which the pressure is to be reduced.
The diffused vapour and entrained
gas molecules are condensed on the
cooled walls of the pump. Pressures
down to 10
–7 Pa can be reached by sophisticated forms of the diffusion
pump.
diffusive Ûux See fick’s law.
dihedral (dihedron) An angle
formed by the intersection of two
planes (e.g. two faces of a polyhedron). The dihedral angle is the angle
formed by taking a point on the line
of intersection and drawing two lines
from this point, one in each plane,
perpendicular to the line of intersection.
dihydrate A crystalline hydrate
containing two moles of water per
mole of compound.
dihydric alcohol See diol.
dihydrogen The normal form of
molecular hydrogen, H 2 , used to distinguish it from hydrogen atoms.
1,2-dihydroxybenzene (catechol)
A colourless crystalline phenol,
C 6 H 4 (OH) 2 ; r.d. 1.15; m.p. 105°C; b.p.
245°C. It is used as a photographic
developer.
1,3-dihydroxybenzene (resorcinol)
A colourless crystalline aromatic
compound, C 6 H 4 (OH) 2 ; m.p. 111°C. It
is made by the fusion of benzenedisulphonic acid with sodium hydroxide and used mainly in the
dyestuffs industry. On fusing with
phthalic anhydride it forms Ûuorescein dyes. It is also used to make
cold-setting adhesives (with
methanal), plasticizers, and resins.
2,3-dihydroxybutanedioic acid
See tartaric acid.
diketones Organic compounds that
have two carbonyl (>C=O) groups (see
ketones). There are three kinds, depending on the location of the carbonyl groups. 1,2-Diketones (also
called α-diketones), R.CO.CO.R′, have
the carbonyl groups on adjacent
carbon atoms. The aliphatic 1,2diethanolamine
176
d
www.AzShimi.ir www.AzShimi.com
diethyl ether See ethoxyethane.
differential scanning calorimetry (DSC) See thermal analysis.
differential thermal analysis
(DTA) See thermal analysis.
diffusion 1. The process by which
different substances mix as a result
of the random motions of their component atoms, molecules, and ions.
In gases, all the components are perfectly miscible with each other and
mixing ultimately becomes nearly
uniform, though slightly affected by
gravity (see also graham’s law). The
diffusion of a solute through a solvent to produce a solution of uniform concentration is slower, but
otherwise very similar to the process
of gaseous diffusion. In solids, diffusion occurs very slowly at normal
temperatures. See also fick’s law.
2. The passage of elementary particles through matter when there is a
high probability of scattering and a
low probability of capture.
diffusion constant See fick’s law.
diffusion gradient See concentration gradient.
diffusion limited aggregation
(DLA) A process of aggregation dominated by particles diffusing and having a nonzero probability of sticking
together irreversibly when they
touch. The clusters formed by DLA
are *fractal in type.
diffusion pump (condensation
pump) A vacuum pump in which oil
or mercury vapour is diffused
through a jet, which entrains the gas
molecules from the container in
which the pressure is to be reduced.
The diffused vapour and entrained
gas molecules are condensed on the
cooled walls of the pump. Pressures
down to 10
–7 Pa can be reached by sophisticated forms of the diffusion
pump.
diffusive Ûux See fick’s law.
dihedral (dihedron) An angle
formed by the intersection of two
planes (e.g. two faces of a polyhedron). The dihedral angle is the angle
formed by taking a point on the line
of intersection and drawing two lines
from this point, one in each plane,
perpendicular to the line of intersection.
dihydrate A crystalline hydrate
containing two moles of water per
mole of compound.
dihydric alcohol See diol.
dihydrogen The normal form of
molecular hydrogen, H 2 , used to distinguish it from hydrogen atoms.
1,2-dihydroxybenzene (catechol)
A colourless crystalline phenol,
C 6 H 4 (OH) 2 ; r.d. 1.15; m.p. 105°C; b.p.
245°C. It is used as a photographic
developer.
1,3-dihydroxybenzene (resorcinol)
A colourless crystalline aromatic
compound, C 6 H 4 (OH) 2 ; m.p. 111°C. It
is made by the fusion of benzenedisulphonic acid with sodium hydroxide and used mainly in the
dyestuffs industry. On fusing with
phthalic anhydride it forms Ûuorescein dyes. It is also used to make
cold-setting adhesives (with
methanal), plasticizers, and resins.
2,3-dihydroxybutanedioic acid
See tartaric acid.
diketones Organic compounds that
have two carbonyl (>C=O) groups (see
ketones). There are three kinds, depending on the location of the carbonyl groups. 1,2-Diketones (also
called α-diketones), R.CO.CO.R′, have
the carbonyl groups on adjacent
carbon atoms. The aliphatic 1,2diethanolamine
176
d
www.AzShimi.ir www.AzShimi.com