drying agent [CHEM] Soluble or insoluble chemical substance that has such a great affinity for water that it will abstract water from a great many fluid materials; soluble chemicals are calcium chloride and glycerol, and insoluble chemicals are bauxite and silica gel. Also known as desiccant. {drı¯⭈iŋ a¯⭈jənt }
dry point [ANALY CHEM] The temperature at which the last drop of liquid evaporates from the bottom of the flask. {drı¯ po˙int }
dual-function catalystSee bifunctional catalyst. {¦du¨l ¦fənk⭈shən kad⭈ə⭈list } dubnium [CHEM] A chemical element, symbolized Db, atomic number 105, a synthetic
element; the thirteenth transuranium element. {du¨b⭈ne¯⭈əm } Duhem’s equationSee Gibbs-Duhem equation. { du˙emz ikwa¯⭈zhən }
Du¨hring’s rule [PHYS CHEM] The rule that a plot of the temperature at which a liquid exerts a particular vapor pressure against the temperature at which a similar reference liquid exerts the same vapor pressure produces a straight or nearly straight line.
{dir⭈iŋz ru¨l }
dulcitol [ORG CHEM] C6H8(OH)6A sugar with a slightly sweet taste; white, crystalline powder with a melting point of 188.5⬚C; soluble in hot water; used in medicine and bacteriology. {dəl⭈səto˙l }
dulcoseSee dulcitol. {dəlko¯s }
Dumas method [ANALY CHEM] A procedure for the determination of nitrogen in organic substances by combustion of the substance. {du¨⭈ma¨ meth⭈əd }
dunniteSee ammonium picrate. {dənı¯t }
duplicate measurement [ANALY CHEM] An additional measurement made on the same (identical) sample of material to evaluate the variance in the measurement. {¦du¨p⭈
lə⭈kət mezh⭈ər⭈mənt }
duplicate sample [ANALY CHEM] A second sample randomly selected from a material being analyzed in order to evaluate sample variance. {¦du¨p⭈lə⭈kət sam⭈pəl } durable-press resinSee permanent-press resin. {¦du˙r⭈ə⭈bəl ¦pres rez⭈ən }
durene [ORG CHEM] C6H2(CH3)4Colorless crystals with camphor aroma; boiling point 190⬚C; soluble in organic solvents, insoluble in water; used as a chemical intermedi-ate. Also known as durol. {du˙re¯n }
durolSee durene. {du˙ro¯l }
Dutch liquidSee ethylene chloride. {¦dəch ¦lik⭈wəd } DySee dysprosium.
dye [CHEM] A colored substance which imparts more or less permanent color to other materials. Also known as dyestuff. { dı¯ }
dyeing assistant [CHEM] Material such as sodium sulfate added to a dye bath to control or promote the action of a textile dye. {dı¯⭈iŋ əsis⭈tənt }
dyestuffSee dye. {dı¯stəf }
dynamic allotropy [CHEM] A phenomenon in which the allotropes of an element exist in dynamic equilibrium. { dı¯¦nam⭈ik əla¨⭈trə⭈pe¯ }
dypnone [ORG CHEM] C6H5COCHC(CH3)C6H5A light-colored liquid with a boiling point of 246⬚C at 50 mmHg; used as a plasticizer and perfume base and in light-stable coatings. {dipno¯n }
Dyson notation [ORG CHEM] A notation system for representing organic chemicals developed by G. Malcolm Dyson; the compound is described on a single line, symbols are used for the chemical elements involved as well as for the functional groups and various ring systems; for example, methyl alcohol is C.Q and phenol is B6.Q.
{dı¯⭈sən no¯ta¯⭈shən }
dysprosium [CHEM] A metallic rare-earth element, symbol Dy, atomic number 66, atomic weight 162.50. { dispro¯⭈ze¯⭈əm }
dystetic mixture [PHYS CHEM] A mixture of two or more substances that has the highest possible melting point of all mixtures of these substances. { disted⭈ik miks⭈chər }
E
eagle mounting [SPECT] A mounting for a diffraction grating, based on the principle of the Rowland circle, in which the diffracted ray is returned along nearly the same direction as the incident beam. {e¯⭈gəl mau˙n⭈tiŋ }
easin [ORG CHEM] C20H6O5I4Na2The sodium salt of tetraiodofluorescein; a brown pow-der, insoluble in water; used as a dye and a pH indicator (hydrogen ion) at pH 2.0.
Also known as iodoeasin; sodium tetrafluorescein. {e¯⭈ə⭈zən }
ebulliometer [PHYS CHEM] The instrument used for ebulliometry. Also known as ebul-lioscope. {əbu˙⭈le¯a¨m⭈əd⭈ər }
ebulliometry [PHYS CHEM] The precise measurement of the absolute or differential boiling points of solutions. {əbu˙⭈le¯a¨m⭈ə⭈tre¯ }
ebullioscopeSee ebulliometer. {əbu˙⭈le¯⭈əsko¯p }
ebullioscopic constant [PHYS CHEM] The ratio of the elevation of the boiling point of a solvent caused by dissolving a solute to the molality of the solution, taken at extremely low concentrations. Also known as molal elevation of the boiling point.
{ ebu¨⭈le¯⭈əsko¯p⭈ik ka¨n⭈stənt }
ecgonine [ORG CHEM] C9H15NO3An alkaloid obtained in crystalline form by the hydrol-ysis of cocaine. {ek⭈gəne¯n }
echelette grating [SPECT] A diffraction grating with coarse groove spacing, designed for the infrared region; has grooves with comparatively flat sides and concentrates most of the radiation by reflection into a small angular coverage. {¦esh⭈ə¦let or
¦a¯sh¦let gra¯d⭈iŋ }
echelle grating [SPECT] A diffraction grating designed for use in high orders and at angles of illumination greater than 45⬚ to obtain high dispersion and resolving power by the use of high orders of interference. { a¯shel gra¯d⭈iŋ }
echelle spectrograph [SPECT] A spectrograph that employs gratings intended to be used in very high orders (greater than 10), and is equipped with a second dispersal element (another grating or a prism) at right angles to the first in order to separate the successive spectral strips from each other. { eshel spek⭈trəgraf }
echelon grating [SPECT] A diffraction grating which consists of about 20 plane-parallel plates about 1 centimeter thick, cut from one sheet, each plate extending beyond the next by about 1 millimeter, and which has a resolving power on the order of 106. {esh⭈əla¨n gra¯d⭈iŋ }
echinopsine [ORG CHEM] C10H9O An alkaloid obtained from Echinops species; crystal-lizes as needles from benzene solution, melts at 152⬚C; physiological action is similar to that of brucine and strychnine. {ek⭈əna¨pse¯n }
eclipsed conformation [PHYS CHEM] A particular arrangement of constituent atoms that may rotate about a single bond in a molecule; for ethane it is such that when viewed along the axis of the carbon-carbon bond the hydrogen atoms of one methyl group are exactly in line with those of the other methyl group. { iklipst ka¨n⭈
fərma¯⭈shən }
edge-bridging ligand [ORG CHEM] A ligand that forms a bridge over one edge of the polyhedron of a metal cluster structure. {ej brij⭈iŋ lı¯⭈gənd }
EDTASee ethylenediaminetetraacetic acid.
EDTCSee S-ethyl-N,N-dipropylthiocarbamate.
EELSSee electron energy loss spectroscopy.
eff
effSee efficiency.
effective molecular diameter [PHYS CHEM] The general extent of the electron cloud surrounding a gas molecule as calculated in any of several ways. {ə¦fek⭈tivməlek⭈
yə⭈lər dı¯am⭈əd⭈ər }
effective permeability [PHYS CHEM] The observed permeability exhibited by a porous medium to one fluid phase when there is physical interaction between this phase and other fluid phases present. {ə¦fek⭈tivpər⭈me¯⭈əbil⭈əd⭈e¯ }
effervescence [CHEM] The bubbling of a solution of an element or chemical compound as the result of the emission of gas without the application of heat; for example, the escape of carbon dioxide from carbonated water. {ef⭈ərves⭈əns }
efflorescence [CHEM] The property of hydrated crystals to lose water of hydration and crumble when exposed to air. {ef⭈ləres⭈əns }
effusion [PHYS CHEM] The movement of a gas through an opening which is small as compared with the average distance which the gas molecules travel between colli-sions. { efyu¨⭈zhən }
EGASee evolved gas analysis.
EGTSee ethylene glycol bis(trichloroacetate).
Ehrlich’s reagent [ORG CHEM] (CH3)2NC6H4CHO Granular or leafletlike crystals that are soluble in many organic solvents; melting point is 74⬚C; used in the preparation of dyes, as a reagent for arsphenamine, anthranilic acid, antipyrine, indole, and skatole, and as a differentiating agent between true scarlet fever and serum eruptions. {er⭈
liks re¯a¯⭈jənt }
eicosanoic acid [ORG CHEM] CH3(CH2)18COOH A white, crystalline, saturated fatty acid, melting at 75.4⬚C; a constituent of butter. Also known as arachic acid; arachidic acid. {¦ı¯⭈kə⭈sə¦no¯⭈ik as⭈əd }
Einschluss thermometer [ANALY CHEM] All-glass, liquid-filled thermometer, tempera-ture range⫺201 to ⫹360⬚C, used for laboratory test work. { ı¯nshlu˙s thərma¨m⭈
əd⭈ər }
einsteinium [CHEM] Synthetic radioactive element, symbol Es, atomic number 99; dis-covered in debris of 1952 hydrogen bomb explosion; now made in cyclotrons.
{ ı¯nstı¯n⭈e¯⭈əm }
Einstein photochemical equivalence law [PHYS CHEM] The law that each molecule taking part in a chemical reaction caused by electromagnetic radiation absorbs one photon of the radiation. Also known as Stark-Einstein law. {ı¯nstı¯n ¦fo¯d⭈o¯¦kem⭈
ə⭈kəl ikwiv⭈ə⭈ləns lo˙ }
Einstein viscosity equation [PHYS CHEM] An equation which gives the viscosity of a sol in terms of the volume of dissolved particles divided by the total volume.
{ı¯nstı¯n v iska¨s⭈əd⭈e¯ ikwa¯⭈zhən }
elaidic acid [ORG CHEM] CH3(CH2)7CH:CH(CH2)7COOH A transisomer of an unsaturated fatty acid, oleic acid; crystallizes as colorless leaflets, melts at 44⬚C, boils at 288⬚C (100 mmHg), insoluble in water, soluble in alcohol and ether; used in chromatography as a reference standard. {¦el⭈ə¦id⭈ik as⭈əd }
elaidinization [ORG CHEM] The process of changing the geometric cis form of an unsatu-rated fatty acid or a compound related to it into the trans form, resulting in an acid that is more resistant to oxidation. {ə¦la¯⭈ədin⭈əza¯⭈shən }
elaidin reaction [ANALY CHEM] A test that differentiates nondrying oils such as olein from semidrying oils and drying oils; nitrous acid converts olein into its solid isomer, while semidrying oils in contact with nitrous acid thicken slowly, and drying oils such as tung oil become hard and resinous. {əla¯⭈əd⭈ən re¯ak⭈shən }
Elbs reaction [ORG CHEM] The formation of anthracene derivatives by dehydration and cyclization of diaryl ketone compounds which have a methyl group or methylene group; heating to an elevated temperature is usually required. {elbs re¯ak⭈shən } ELDORSee electron electron double resonance. {eldo˙r or ¦e¯¦el¦de¯¦o¯a¨r }
electrical calorimeter [ANALY CHEM] Device to measure heat evolved (from fusion or vaporization, for example); measured quantities of heat are added electrically to the sample, and the temperature rise is noted. {əlek⭈trə⭈kəl kal⭈ərim⭈əd⭈ər }