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Home >> Chemistry Dictionary >>Eudiometer - Explosion
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Ethyl nitrite (Nitrous Ether, C2H5NO2).
A volatile liquid with a sweet smell, b.p. 17°C, used in medicine.
Ethyne, acetylene.
C2H2, HC º CH. Colourless gas which when pure has a pleasant smell. M.p. - 82°C, b.p. - 84°C. The compound has very wide explosive limits in air (2.3% and 80% Ethyne by volume) and apart from this the liquid, and also the gas if the pressure exceeds 2 atm., are explosive even in the absence of air. For storage and transportation steel cylinders containing propanone and a porous material such as diatomaceous earth are used.
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Like all terminal alkynes, the ethynic hydrogen atoms are acidic in the sense that they are removed by suitable strong bases such as sodamide or a Grignard reagent to give RC º Can or RC º CMgX. (For Ethyne R = H, although a second mole of base will also replace this hydrogen atom). Many metals will give salts (see acetylides) which may be used for purification purposes, e.g. silver acetylide, AgC º CH, a white shock – sensitive solid, insoluble in water, regenerates Ethyne on treatment with mineral acids.
Eu.
Europium.
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Eudiometer.
An apparatus for measuring changes in volume of gases during chemical reactions. A simple example is a graduated glass tube sealed at one end and inverted in mercury. Wires passing into the tube allow the gas mixture to be sparked to initiate the reaction between gases in the tube.
Europium.
Symbol Eu. A soft silvery metallic element belonging to the lanthanoids; a.n. 63; r.a.m. 151.96; r.d. 5.245 (20°C; m.p. 822°C; b.p. 1529°C. It occurs in small quantities in bastanite and monazite. Two stable isotopes occur naturally; europium – 151 and europium - 153 both of which are neutron absorbers. Experimental europium alloys have been tried for nuclear – reactor parts but until recently the metal has not been available in sufficient quantities. Additional uses are being researched since the metal become available in large quantities.
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Eutectic.
When a mechanical mixture of two substances shows a sharp melting point, the mixture is said to be a eutectic mixture. The temperature at which this occurs is called the eutectic temperature.
EVA plastics.
Copolymers of ethane and vinyl acetate (vinyl ethanoate).
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Evaporation.
The change of state of a liquid into a vapour at a temperature below the boiling point of the liquid Evaporation occurs at the surface of a liquid, some of those molecules with the highest kinetic energies escaping into the gas phase. The result is a fall in the average kinetic energy of the molecules with the highest kinetic energies escaping into the gas phase. The result is a fall in the average kinetic energy of the molecules of the liquid and consequently a fall in its temperature.
Excitation energy.
The energy needed to change an atom. molecule etc. from one quantum state to a state with a higher energy.
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Excited state.
A state of an atom, molecule, etc. when the species has absorbed energy and become excited to a higher energy state as compared with the ground state. The excitation may be electronic, vibrational, rotational, etc.
Exothermic reaction.
A reaction which is accompanied by release of heat, as burning of coal.
Explosion.
Rapid combustion in homogeneous fuel/air mixtures with the flame front passing through the mixture from the source of ignition. Explosions may occur in constant pressure or constant volume situations. In the former there are only local pressure increases at the flame from where the reaction is completed but there are no significant pressure increase in the passage way or shaft. In constant volume explosions the flame front spreads very rapidly across the container or cylinder and high turbulence creates rapid flame propagation, giving an irregular flame front and then high pressure increases.
Extender.
A compounding ingredient, frequently only a filler, for rubber.
Extensive property.
A property that is independent of the amount of matter, e.g. density, melting point, odour, resistivity, specific heat, capacity etc.
Extract.
In solvent extraction a portion of the feed is preferentially dissolved by the solvent and recorded by distilling off the solvent. This constitutes the extract.
Extra nuclear structure.
The structure of an atom outside its nucleus. It describes the arrangement of electrons in electron shells surrounding a nucleus.
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