excitation spectrum [SPECT] The graph of luminous efficiency per unit energy of the exciting light absorbed by a photoluminescent body versus the frequency of the exciting light. {eksı¯ta¯⭈shən spek⭈trəm }
exciting line [SPECT] The frequency of electromagnetic radiation, that is, the spectral line from a noncontinuous source, which is absorbed by a system in connection with some particular process. { eksı¯d⭈iŋ lı¯n }
exhaustion point [CHEM] In an ion-exchange process, the state of an adsorbent at which it no longer can produce a useful ion exchange. { igzo˙s⭈chən po˙int } exo- [ORG CHEM] A conformation of carbon bonds in a six-membered ring such that
the molecule is boat-shaped with one or more substituents directed outward from the ring. {ek⭈so¯ }
exocyclic double bond [ORG CHEM] A double bond that is connected to and external to a ring structure. {¦ek⭈so¯¦sı¯⭈klik ¦dəb⭈əl ba¨nd }
explosion [CHEM] A chemical reaction or change of state which is effected in an exceedingly short space of time with the generation of a high temperature and generally a large quantity of gas. { iksplo¯⭈zhən }
extender [CHEM] A material used to dilute or extend or change the properties of resins, ceramics, paints, rubber, and so on. { iksten⭈dər }
extensive property [PHYS CHEM] A noninherent property of a system, such as volume or internal energy, that changes with the quantity of material in the system; the quantitative value equals the sum of the values of the property for the individual constituents. { iksten⭈siv pra¨p⭈ərd⭈e¯ }
external circuit [PHYS CHEM] All connecting wires, devices, and current sources which achieve desired conditions within an electrolytic cell. { ekstərn⭈əl sər⭈kət } external phaseSee continuous phase. { ekstərn⭈əl fa¯z }
extinctionSee absorbance. { ekstiŋk⭈shən }
extinction coefficientSee absorptivity. { ekstiŋk⭈shən ko¯⭈ifish⭈ənt }
extract [CHEM] Material separated from liquid or solid mixture by a solvent. {ek
strakt (noun) or ikstrakt (verb) }
extractant [CHEM] The liquid used to remove a solute from another liquid. { ik
strak⭈tənt }
extracting agent [CHEM] In a liquid-liquid distribution, the reagent forming a complex or other adduct that has different solubilities in the two immiscible liquids of the extraction system. { ikstrak⭈tiŋ a¯⭈jənt }
extraction [CHEM] A method of separation in which a solid or solution is contacted with a liquid solvent (the two being essential mutually insoluble) to transfer one or more components into the solvent. { ikstrak⭈shən }
extreme narrowing approximation [SPECT] A mathematical approximation in the the-ory of spectral-line shapes to the effect that the exchange narrowing of a perturbation is complete. { ekstre¯m nar⭈ə⭈wiŋ əpra¨k⭈səma¯⭈shən }
extrinsic sol [PHYS CHEM] A colloid whose stability is attributed to electric charge on the surface of the colloidal particles. { ek¦strinz⭈ik sa¨l }
Eyring equation [PHYS CHEM] An equation, based on statistical mechanics, which gives the specific reaction rate for a chemical reaction in terms of the heat of activation, entropy of activation, the temperature, and various constants. {ı¯⭈riŋ ikwa¯⭈zhən }
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F
FSee fluorine.
face-bridging ligand [ORG CHEM] A ligand that forms a bridge over one triangular face of the polyhedron of a metal cluster structure. {fa¯s brij⭈iŋ lı¯g⭈ənd }
family [CHEM] A group of elements whose chemical properties, such as valence, solubil-ity of salts, and behavior toward reagents, are similar. {fam⭈le¯ }
famphur [ORG CHEM] C10H16NO5PS2A crystalline compound with a melting point of 55⬚C; slightly soluble in water; used as an insecticide for lice and grubs of reindeer and cattle. {fam⭈fər }
faradaic currentSee faradic current. {far⭈ə¦da¯⭈ik ¦kər⭈ənt }
Faraday’s laws of electrolysis [PHYS CHEM] 1.The amount of any substance dissolved or deposited in electrolysis is proportional to the total electric charge passed.
2.The amounts of different substances dissolved or desposited by the passage of the same electric charge are proportional to their equivalent weights. {far⭈əda¯z
¦lo˙z əv ilektra¨l⭈ə⭈səs }
fast chemical reaction [PHYS CHEM] A reaction with a half-life of milliseconds or less;
such reactions occur so rapidly that special experimental techniques are required to observe their rate. {fast ¦kem⭈ə⭈kəl re¯ak⭈shən }
fatty acid [ORG CHEM] An organic monobasic acid of the general formula CnH2n+1COOH derived from the saturated series of aliphatic hydrocarbons; examples are palmitic acid, stearic acid, and oleic acid; used as a lubricant in cosmetics and nutrition, and for soaps and detergents. {¦fad⭈e¯ as⭈əd }
fatty alcohol [ORG CHEM] A high-molecular-weight, straight-chain primary alcohol derived from natural fats and oils; includes lauryl, stearyl, oleyl, and linoleyl alcohols;
used in pharmaceuticals, cosmetics, detergents, plastics, and lube oils and in textile manufacture. {fad⭈e¯ al⭈kəho˙l }
fatty amine [ORG CHEM] RCH2NH2A normal aliphatic amine from oils and fats; used as a plasticizer, in medicine, as a chemical intermediate, and in rubber manufacture.
{fad⭈e¯ ame¯n }
fatty ester [ORG CHEM] RCOOR⬘ A fatty acid in which the alkyl group (R⬘) of a monohy-dric alcohol replaces the active hydrogen; for example, RCOOCH3from reaction of RCOOH with methane. {fad⭈e¯ es⭈tər }
fatty nitrile [ORG CHEM] RCN An ester of hydrogen cyanide derived from fatty acid;
used in lube oil additives and plasticizers, and as a chemical intermediate. {fad⭈
e¯nı¯trəl }
Favorskii rearrangement [ORG CHEM] A reaction in which ␣-halogenated ketones undergo rearrangement in the presence of bases, with loss of the halogen and formation of carboxylic acids or their derivatives with the same number of carbon atoms. { favo˙r⭈ske¯ re¯⭈əra¯nj⭈mənt }
FCCSee chlorofluorocarbon.
FeSee iron.
feedback [CHEM] In a stepwise reaction, the formation of a substance in one step that affects the rate of a previous step. {fe¯dbak }
Fehling’s reagent [ANALY CHEM] A solution of cupric sulfate, sodium potassium tar-trate, and sodium hydroxide, used to test for the presence of reducing compounds such as sugars. {fa¯l⭈iŋz re¯a¯⭈jənt }