`Chemistry
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`FIFTH EDITION
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`Edited by
`JOHN DAINTITH
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`OXFORD
`UNIVERSITY PRESS
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`APPLE 1023
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`APPLE 1023
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`OXFORD
`UNIVERSITY PRESS
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`Great Clarendon Street. Oxford 0X2 GDP
`
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`intheUKandincertainothercounlris
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`0 Market House Books Ltd. 1985. 1990. 1996. 2000. 2004
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`The moral rights of the author have been asserted
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`Database right Oxford University Press (maker)
`
`First published 1985 as A Concise Dictionary ofamnistry
`Second edition 1990
`Third edition 1996
`Fourth edition 2000
`Fifth edition 2004
`
`All rights reserved. No part of this publication may be Rpmuced-
`stored in a retrieval system. or transmitted in any form or by any means-
`‘
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`British Library Cataloguing in Publication Data
`Data available
`
`Library of Congress Cataloging in Publication Data
`Data available
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`ISBN 0496609188
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`1 T
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`ypesetinSwifibyMar-ketl-hrsesooksud.
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`Printedincrear BfiuinbyflaysMStlvupk
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`2
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`Planck constant
`f—N
`became a professor at Berlin University in 1892. Here he fOTmula
`*qualltllm theory, which had its basis in a paper of 1900‘ One of ttlfd the
`important scientific discoveries of the century, this Work Earned 111:]th
`1918 Nobel Prize for physics.
`the
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`Planck constant Symbol h. The fundamental constant equal to the
`of the energy of a quantum of energy to its frequency. It has the val
`6.626 0755(40) x 10—34 J s. It is named after Max Planck. In quantum-
`mechanical calculations the rationalized Planck constant (or Dirac can
`it = mm: = 1.054 589 x 10““) s is frequently used.
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`stunt)
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`ratio
`ue
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`plane-polarized light See polarization of light.
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`plaster of Paris The hemihydrate of *calcium sulphate, 2Caso+H 0
`prepared by heating the mineral gypsum. When ground to a fine paid.)
`and mixed with water, plaster of Paris sets hard, forming interlocking
`crystals of gypsum. The setting results in an increase in volume and so the
`plaster fits tightly into a mould. It is used in pottery making, as a cast for
`setting broken bones, and as a constituent of the plaster used in the
`building industry.
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`plasticizer A substance added to a synthetic resin to make it flexible. See
`plastics.
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`plastics Materials that can be shaped by applying heat or pressure. Most
`plastics are made from polymeric synthetic *resins, although a few are
`based on natural substances (e.g. cellulose derivatives or shellac). They fall
`into two main classes. Thermoplastic materials can be repeatedly softened by
`heating and hardened again on cooling. Thermosetting materials are initially
`'soft, but change irreversibly to a hard rigid form on heating. Plastics
`contain the synthetic resin mixed with such additives as pigments,
`plasticizers (to improve flexibility), antioxidants and other stabilizers.
`fillers. See Chronology.
`dent
`plastocyanin A blue copper-containing protein that is found in
`chloroplasts and acts as an electron carrier molecule in the hght-dePen _
`.
`_
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`.
`.
`-
`1n
`reactions of *photosynthesrs. Plastocyamn con51sts of ammo and gfopps
`association with a copper molecule which gives this compound a b u
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`and
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`colour.
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`ts, that functions as one of
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`hain in the light
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`plastoquinone A quinone, found in chloroplas
`the carrier molecules of the electron transport c
`dependent reactions of *photosynthesis.
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`*transition element (59
`o
`platinum Symbol Pt. A silvery white metallic
`.
`platinum metals); an. 78; ram. 195.09; r.d. 21.45; mp. 1772_ C' b'p'found
`3827i100°C. It occurs in some nickel and copper ores and 15 8153mmed in
`native in some deposits. The main source is the anode Sludge oatol'Y
`copper—nickel refining. The element is used in jewellery, labfarcts
`apparatus (e.g. thermocouples, electrodes, etc), e1ectr1ca1 CO: 0 en’
`certain alloys (e.g. with iridium or rhodium). It is also a hy r 3
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`3
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`e, a plastic
`er called
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`Scottish chemist Charles Macintosh (1766—1843) ma
`kes ebonite (from
`rubber)-
`British chemist Alexander Parkes (1813—90) patents Parkesin
`made from nitrocellulose, methanol, and wood pulp; it is lat
`’celluloid'.
`British chemist Charles Williams (1829—1910) prepares isoprene (synthetic
`rubber).
`US printer 10hr} Hyatt (18374 920) develops commercial process for
`making celluloud.
`French chemist Hilaire de Chardonnet (1839—1924) develops process for
`making rayon.
`British chemists Edward Bevan (1856—1921) and Charles Cross
`(1855—1935) develop the Viscose process for making rayon.
`British chemist Frederick Kipping (1863—1949) discovers silicone plastics,
`German chemists Krische and Spitteler make formaldehyde—casein plastic
`(Galalith).
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`Belgian-born US chemist Leo Baekland (1863—1944)'invents Bakelite.
`Swiss chemist Jacques Brandenberger produces Cellophane (viscose
`cellulose film).
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`US Formica Insulation company markets plastic laminate made from
`formaldehyde resins.
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`Hans John prepares urea-formaldehyde resin.
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`German chemist Hermann Staudinger (1881-1965) discovers the
`polymeric nature of plastics.
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`US chemist Waldo Semon develops PVC (polyvinyl chloride).
`Canadian chemist William Chalmers discovers polymethylmethacrylate
`(Perspex and Plexiglass).
`German chemists at IG Farbenindustrie produce polystyrene.
`Wallace Carothers invents nylon.
`'
`US chemist Roy Plunkett produces polYtetrafluorOEthene (PTFE)
`British company lCl develops commercial process for making p0lyethene.
`{BDritish chemists John Whinfield (1901—66) and J. Dickson develop Terylene
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`acron)_
`German company IG Farbenindustrie produces polyurethane.
`U5 Dow Corning company produces silicone plastics._ ..
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`‘
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`British chemists produce acrylic fibres.
`Serman chemist Karl Ziegler (1896—1973) discovers'cata
`lgh-denSIty polyethene.
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`Malia." Chemist Giulio Natta (1903—79) develops industrial‘Process for
`mak'”9 hiQh‘density polyethene (using Ziegler, catalYSt)
`Italian company Ferruzzi produces biodegradf-‘b'e plastic
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`(based on starch).
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`iyst for making
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`4
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`retort
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`r 4
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`35
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`. A synthetic or naturally occurring *polyiner. Synthetic resins are
`r95!" making *plastics. Natural resms are ac1dic chemicals secreted by
`.
`S (especially conifers) into ducts or canals. They are found either
`used ”1 ee
`y tr
`lassy substances or dissolved in essential oils. Their
`.
`functions are
`s brittle g
`D bly similar to those of gums and InuCilages.
`r0 3
`olution The process of separating a racemic mixture into its optically
`as
`We Constituents. In some cases the crystals of the two forms have a
`ac 1
`different appearance, and the separation can be done by hand. In general,
`however, PhYSical methods (distillation, crystallization, etc.) cannot be used
`cause the optical isomers have identical phySical properties. The most
`bsmmon technique is to react the mixture With a compound that is itself
`Spatially active, and theft separate the two. For Instance, a racemic mixture
`of M and d-A reacted With 1—3 g1ves two compounds AB that are not
`optical isomers but diastere01somers and can be separated and reconverted
`into the pure l-A and d-A, Biological techniques using bacteria that convert
`one form but not the other can also be used.
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`a P
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`resonance The representation of the structure of a molecule by two or
`more conventional formulae. For example, the formula of methanal can be
`represented by a covalent structure H2C=O, in which there is a double bond
`in the carbonyl group. It is known that in such compounds the oxygen has
`some negative charge and the carbon some positive charge. The true
`bonding in the molecule is somewhere between H2C=O and the ionic
`compound HZOO‘. It is said to be a resonance hybrid of the two, indicated by
`H2C=O H H2C+O~
`
`The two possible structures are called canonical forms, and they need not
`contribute equally to the actual form. Note that the double-headed arrow
`does not imply that the two forms are in equilibrium.
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`resonance effect See electronic effects.
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`”Swami: ionization spectroscopy (RIS) A spectroscopic technique in
`Wthh Single atoms in a gas are detected using a laser to ionize that atom.
`A SHHlple containing the atoms to be excited is subjected to light from a
`laser, tuned so that only that type of atom is excited by the light. If the
`freqilency 0f light at which the atom is excited is v, the atoms in the
`med State Can be ionized if the ionization potential of the atom 18 less
`iomzfgéln Conn-“St to other techniques of ionization, this type of
`light Ben only (me-111's for atoms that are ‘in tune’ With the frequency of
`'
`cause R18 is very selective in determining which atom 13 ionized for
`a
`i
`'
`r men frequency It has many applications in chemistry.
`esorcmol See L3'dihydr0xybenzene.
`.
`retmol See Vitamin A.
`“(1:51. A laboratol'y apparatus consisting of a glass bulb With a long
`Pmcesse: vessfl u56d for reaction or distillation in industrial chemical
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`Elihu-‘
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`5
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