actinochemistry

actinochemistry [CHEM] A branch of chemistry concerned with chemical reactions

produced by light or other radiation.

actinium

actinium [CHEM] A radioactive element, symbol Ac, atomic number 89; its longest-

lived isotope is 227

Ac with a half-life of 21.7 years; the element is trivalent; chief use

is, in equilibrium with its decay products, as a source of alpha rays.

actinism

actinism [CHEM] The production of chemical changes in a substance upon which elec-

tromagnetic radiation is incident.

actinide series

actinide series [CHEM] The group of elements of atomic number 89 through 103. Also

known as actinoid elements.

acrylonitrile butadiene styrene resin

acrylonitrile butadiene styrene resin [ORG CHEM] A polymer made by blending acrylo-

nitrile-styrene copolymer with a butadiene-acrylonitrile rubber or by interpolymeriz-

ing polybutadiene with styrene and acrylonitrile; combines the advantages of

hardness and strength of the vinyl resin component with the toughness and impact

resistance of the rubbery component. Abbreviated ABS.

acrylonitrile copolymer

acrylonitrile copolymer [ORG CHEM] Oil-resistant synthetic rubber made by polymer-

ization of acrylonitrile with compounds such as butadiene or acrylic acid.

acrylic rubber

acrylic rubber [ORG CHEM] Synthetic rubber containing acrylonitrile; for example,

nitrile rubber.

acrylonitrile

acrylonitrile [ORG CHEM]CH2CHCN A colorless liquid compound used in the manufac-

ture of acrylic rubber and fibers. Also known as vinylcyanide.

acrylic ester

acrylic ester [ORG CHEM] An ester of acrylic acid.

acrylic resin

acrylic resin [ORG CHEM] A thermoplastic synthetic organic polymer made by the poly-

merization of acrylic derivatives such as acrylic acid, methacrylic acid, ethyl acrylate,

and methyl acrylate; used for adhesives, protective coatings, and finishes.

acrylate resin

acrylate resin [ORG CHEM] Acrylic acid or ester polymer with a CH2 CH(COOR)

structure; used in paints, sizings and finishes for paper and textiles, adhesives, and

plastics. Also known as acrylate.

acrylic acid or

acrylic acid [ORG CHEM]CH2CHCOOHAn easily polymerized, colorless, corrosive liquid

used as a monomer for acrylate resins.

acrylate

acrylate [ORG CHEM] 1. A salt or ester of acrylic acid. 2. See acrylate resin.

acrylamide

acrylamide [ORG CHEM]CH2CHCONH2 Colorless, odorless crystals with amelting point

of 84.5 C; soluble in water, alcohol, and acetone; used in organic synthesis, polymer-

ization, sewage treatment, ore processing, and permanent press fabrics.

acrylamide copolymer

acrylamide copolymer [ORG CHEM] A thermosetting resin formed of acrylamide with

other resins, such as the acrylic resins.

acrolein dimer

acrolein dimer [ORG CHEM]C6H8O2 A flammable, water-soluble liquid used as an inter-

mediate for resins, dyestuffs, and pharmaceuticals.

acrolein test

acrolein test [ANALY CHEM] A test for the presence of glycerin or fats; a sample is

heated with potassium bisulfate, and acrolein is released if the test is positive.

acrolein cyanohydrin

acrolein cyanohydrin [ORG CHEM]CH2:CHCH(OH)CN A liquid soluble in water and

boiling at 165 C; copolymerizes with ethylene and acrylonitrile; used to modify

synthetic resins. 

acrolein

acrolein [ORG CHEM]CH2 CHCHO A colorless to yellow liquid with a pungent odor

and a boiling point of 52.7 C; soluble in water, alcohol, and ether; used in organic

synthesis, pharmaceuticals manufacture, and as an herbicide and tear gas.

acriflavine

acriflavine [ORG CHEM]C14H14N3Cl A yellow acridine dye obtained from proflavine by

methylation in the form of red crystals; used as an antiseptic in solution.

acridine orange

acridine orange [ORG CHEM] A dye with an affinity for nucleic acids; the complexes of

nucleic acid and dye fluoresce orange with RNA and green with DNA when observed

in the fluorescence microscope.

acridine dye

acridine dye [ORG CHEM] Any of a class of basic dyes containing the acridine nucleus

that bind to deoxyribonucleic acid.

acridine

acridine [ORG CHEM](C6H4)2NCH A typical member of a group of organic heterocyclic

compounds containing benzene rings fused to the 2,3 and 5,6 positions of pyridine;

derivatives include dyes and medicines.

aconitic acid

aconitic acid [ORG CHEM]C6H6O6 A white, crystalline organic acid found in sugarcane

and sugarbeet; obtained during manufacture of sugar.

Acree’s reaction

Acree’s reaction [ANALY CHEM] A test for protein in which a violet ring appears when

concentrated sulfuric acid is introduced below amixture of the unknown solution and

a formaldehyde solution containing a trace of ferric chloride.

acid value

acid value Also known as acid number. [CHEM] The acidity of a solution expressed in

terms of normality. [ORG CHEM] A number indicating the amount of nonesterified

fatty acid present in a sample of fat or fatty oil as determined by alkaline titration.

acid tartrate

acid tartrate See bitartrate.

acid sodium tartrate

acid sodium tartrate See sodium bitartrate.

acid solution

acid solution [CHEM] An aqueous solution containing more hydrogen ions than

hydroxyl ions.

acid salt

acid salt [CHEM] A compound derived from an acid and base in which only a part of

the hydrogen is replaced by a basic radical; for example, the acid sulfate NaHSO4.

acid potassium sulfate

acid potassium sulfate See potassium bisulfate.

acid reaction

acid reaction [CHEM] A chemical reaction produced by an acid.

acid phosphate

acid phosphate [INORG CHEM] A mono- or dihydric phosphate; for example, M2HPO4

or MH2PO4, where M represents a metal atom.

acid potassium phthalate

acid potassium phthalate See potassium biphthalate.

acidolysis

acidolysis [ORG CHEM] A chemical reaction involving the decomposition of a molecule,

with the addition of the elements of an acid to the molecule; the reaction is compara-

ble to hydrolysis or alcoholysis, in which water or alcohol, respectively, is used in

place of the acid. Also known as acyl exchange.

acid number

acid number See acid value.

acidity function

acidity function [CHEM] A quantitative scale for measuring the acidity of a solvent

system; usually established over a range of compositions.

acidity

acidity [CHEM] The state of being acid.

acidimeter

acidimeter [ANALY CHEM] An apparatus or a standard solution used to determine the

amount of acid in a sample.

acidimetry

acidimetry [ANALY CHEM] The titration of an acid with a standard solution of base.

acidification

acidification [CHEM] Addition of an acid to a solution until the pH falls below 7.

acidic oxide

acidic oxide [INORG CHEM] An oxygen compound of a nonmetal, for example, SO2 or

P2O5, which yields an oxyacid with water.

acidic titrant

acidic titrant [ANALY CHEM] An acid solution of known concentration used to determine

the basicity of another solution by titration.

acidic group

acidic group [ORG CHEM] The radical COOH, present in organic acids.

acidic dye

acidic dye [ORG CHEM] An organic anion that binds to and stains positively charged

macromolecules.

acidic dye [ORG CHEM] An organic anion that binds to and stains positively charged

macromolecules.

acidic

acidic [CHEM] 1. Pertaining to an acid or to its properties. 2. Forming an acid during

a chemical process.

acid heat test

acid heat test [ANALY CHEM] The determination of degree of unsaturation of organic

compounds by reacting with sulfuric acid and measuring the heat of reaction.

acid halide

acid halide [ORG CHEM] A compound of the type RCOX, where R is an alkyl or aryl

radical and X is a halogen.

acid electrolyte

acid electrolyte [INORG CHEM] A compound, such as sulfuric acid, that dissociates into

ions when dissolved, forming an acidic solution that conducts an electric current.

acid dye

acid dye [ORG CHEM] Any of a group of sodium salts of sulfonic and carboxylic acids

used to dye natural and synthetic fibers, leather, and paper.

acid disproportionation

acid disproportionation [CHEM] The self-oxidation of a sample of an oxidized element

to the next higher oxidation state and then a corresponding reduction to lower

oxidation states.

acid cell

acid cell [PHYS CHEM] An electrolytic cell whose electrolyte is an acid.

acid chloride

acid chloride [ORG CHEM] A compound containing the radical COCl; an example is

benzoyl chloride.

acid cell

acid cell [PHYS CHEM] An electrolytic cell whose electrolyte is an acid.

acid calcium phosphate

acid calcium phosphate See calcium phosphate.

acid-base titration

acid-base titration [ANALY CHEM] A titration in which an acid of known concentration

is added to a solution of base of unknown concentration, or the converse.

acid-base indicator

acid-base indicator [ANALY CHEM] A substance that reveals, through characteristic

color changes, the degree of acidity or basicity of solutions.

acid-base pair

acid-base pair [CHEM] A concept in the Bro ¨ nsted theory of acids and bases; the pair

consists of the source of the proton (acid) and the base generated by the transfer

of the proton.

acid-base equilibrium

acid-base equilibrium [CHEM] The condition when acidic and basic ions in a solution

exactly neutralize each other; that is, the pH is 7.

acid-base catalysis

acid-base catalysis [CHEM] The increase in speed of certain chemical reactions due

to the presence of acids and bases.

acid azide

acid azide [ORG CHEM] 1. A compound in which the hydroxy group of a carboxylic acid

is replaced by the azido group ( NH3). 2. An acyl or aroyl derivative of hydrazoic

acid. Also known as acyl azide.

acid amide

acid amide [ORG CHEM] A compound derived from an acid in which the hydroxyl group

( OH) of the carboxyl group ( COOH) has been replaced by an amino group ( NH2)

or a substituted amino group ( NHR or NHR2).

acid anhydride

acid anhydride [CHEM] An acid with one or more molecules of water removed; for

example, SO3 is the acid anhydride of H2SO4, sulfuric acid.

acid alcohol

acid alcohol [ORG CHEM] A compound containing both a carboxyl group ( COOH)

and an alcohol group ( CH2OH, CHOH, or COH).

acid acceptor

acid acceptor [ORG CHEM] A stabilizer compound added to plastic and resin polymers

to combine with trace amounts of acids formed by decomposition of the polymers.

by acid

by acid [ORG CHEM] An acid that readily forms stable complexes with aromatic systems.

acid

acid [CHEM] 1. Any of a class of chemical compounds whose aqueous solutions turn

blue litmus paper red, react with and dissolve certain metals to form salts, and react

with bases to form salts. 2. A compound capable of transferring a hydrogen ion

in solution. 3. A substance that ionizes in solution to yield the positive ion of the

solvent. 4. Amolecule or ion that combines with anothermolecule or ion by forming

a covalent bond with two electrons from the other species.

achiral molecules

achiral molecules [ORG CHEM] Molecules which are superposable to their mirror

images.

acetyl valeryl

acetyl valeryl [ORG CHEM]CH3COCOC4H9 A yellow liquid used for cheese, butter, and

other flavors. Also known as heptadione-2,3.

acetylurea

acetylurea [ORG CHEM]CH3CONHCONH2 Crystals that are colorless and are slightly

soluble in water. 

N-acetylsulfanilyl chloride

N-acetylsulfanilyl chloride [ORG CHEM]C8H8ClNO3S Thick, light tan prisms ranging to

brown powder or fine crystals with a melting point of 149 C; soluble in benzene,

chloroform, and ether; used as an intermediate in the preparation of sulfanilamide

and its derivatives. Abbreviated ASC. 

acetylsalicylic acid

acetylsalicylic acid [ORG CHEM]CH3COOC6H4COOH A white, crystalline, weakly acidic

substance, with melting point 137 C; slightly soluble in water; used medicinally as

an antipyretic. Also known by trade name aspirin.

acetyl propionyl

acetyl propionyl [ORG CHEM]CH3COCOCH2CH3 A yellow liquid with a boiling point

of 106–110 C; used in butterscotch- and chocolate-type flavors.

acetyl number

acetyl number [ANALY CHEM] A measure of free hydroxyl groups in fats or oils deter-

mined by the amount of potassium hydroxide used to neutralize the acetic acid

formed by saponification of acetylated fat or oil.

acetyl peroxide

acetyl peroxide [ORG CHEM] (CH3CO)2O2 Colorless crystals with a melting point of

30 C; soluble in alcohol and ether; used as an initiator and catalyst for resins.

acetylisoeugenol

acetylisoeugenol [ORG CHEM]C6H3(CHCHCH3)(OCH3)(OCOCH3) White crystals with a

clovelike odor and a congealing point of 77 C; used in perfumery and flavoring.

acetyl iodide

acetyl iodide [ORG CHEM]CH3COI A colorless, transparent, fuming liquid with a boiling

point of 105–108 C; soluble in ether and benzene; used in organic synthesis.

acetylide

acetylide [ORG CHEM] A compound formed from acetylene with the H atoms replaced

by metals, as in cuprous acetylide (Cu2C2).

N-acetylethanolamine

N-acetylethanolamine [ORG CHEM]CH3CONHC2H4OH A brown, viscous liquid with a

boiling range of 150–152 C; soluble in alcohol, ether, and water; used as a plasticizer,

humectant, high-boiling solvent, and textile conditioner.

acetylenyl

acetylenyl See ethinyl.

acetylene tetrabromide

acetylene tetrabromide [ORG CHEM] CHBr2CHBr2 A yellowish liquid with a boiling point

of 239–242 C; soluble in alcohol and ether; used for separating minerals and as a

solvent.

acetylenic

acetylenic [ORG CHEM] Pertaining to acetylene or being like acetylene, such as having

a triple bond.

acetylene series

acetylene series [ORG CHEM] A series of unsaturated aliphatic hydrocarbons, each

containing at least one triple bond and having the general formula CnH2n 2.

acetylene

acetylene [ORG CHEM]C2H2 A colorless, highly flammable gas that is explosive when

compressed; the simplest compound containing a triple bond; used in organic synthe-

sis and as a welding fuel. Also known as ethyne.

acetylene black

acetylene black [ORG CHEM] A form of carbon with high electrical conductivity; made

by decomposing acetylene by heat.

acetyl chloride

acetyl chloride [ORG CHEM]CH3COCl A colorless, fuming liquid with a boiling point

of 51–52 C; soluble in ether, acetone, and acetic acid; used in organic synthesis,

and in the manufacture of dyestuffs and pharmaceuticals.

acetyl bromide

acetyl bromide [ORG CHEM]CH3COBr A colorless, fuming liquid with a boiling point

of 81 C; soluble in ether, chloroform, and benzene; used in organic synthesis and

dye manufacture.

alfa cetylbutyrolactone

alfa cetylbutyrolactone [ORG CHEM]C6H8O3 A liquid with an esterlike odor; soluble in

water; used in the synthesis of 3,4-disubstituted pyridines.

acetylation

acetylation [ORG CHEM] The process of bonding an acetyl group onto an organic mole-

cule.

acetyl benzoyl peroxide

acetyl benzoyl peroxide [ORG CHEM]C6H5CO O2 OCCH3 White crystals with a melting

point of 36.6 C; moderately soluble in ether, chloroform, carbon tetrachloride, and

water; used as a germicide and disinfectant.

acetylating agent

acetylating agent [ORG CHEM] A reagent, such as acetic anhydride, capable of bonding

an acetyl group onto an organic molecule.

acetylacetone

acetylacetone [ORG CHEM]CH3COCH2OCCH3 A colorless liquid with a pleasant odor

and a boiling point of 140.5 C; soluble in water; used as a solvent, lubricant additive,

paint drier, and pesticide.

alfa acetylacetanilide

alfa acetylacetanilide See acetoacetic acid.

acetyl

acetyl [ORG CHEM]CH3CO A two-carbon organic radical containing a methyl group
and a carbonyl group.

acetoxime

acetoxime [ORG CHEM] (CH3)2CNOH Colorless crystals with a chlorallike odor and a
melting point of 61 C; soluble in alcohol, ethers, and water; used in organic synthesis
and as a solvent for cellulose ethers.

aceturic acid

aceturic acid [ORG CHEM]CH3CONHCHCH2COOH Long, needlelike crystals with a
melting point of 206–208 C; soluble in water and alcohol; forms stable salts with
organic bases; used in medicine.

acetophenone

acetophenone [ORG CHEM]C6H5COCH3 Colorless crystals with amelting point of 19.6 C
and a specific gravity of 1.028; used as a chemical intermediate.

acetostearin

acetostearin [ORG CHEM] A general term for monoglycerides of stearic acid acetylated
with acetic anhydride; used as a protective food coating and as plasticizers for waxes
and synthetic resins to improve low-temperature characteristics.

acetonyl acetone

acetonylacetone [ORG CHEM]CH3COCH2CH2COCH3 A colorless liquid with a boiling
point of 192.2 C; soluble in water; used as a solvent and as an intermediate for
pharmaceuticals and photographic chemicals.

acetonitrile

acetonitrile [ORG CHEM]CH3CN A colorless liquid soluble in water; used in organic
synthesis.

acetone sugar

acetone sugar [ORG CHEM] Any reducing sugar that contains acetone; examples are
1,2-monoacetone-D-glucofuranose and 1,2,6-diacetone-D-glucofuranose. Also
known as acetone glucose.

acetone-sodium bisulfite

acetone-sodium bisulfite [ORG CHEM] (CH3)2C(OH)SO3Na Crystals that have a slight
sulfur dioxide odor and slightly fatty feel; freely soluble in water, decomposed by
acids; used in photography and in textile dyeing and printing.

acetone pyrolysis

acetone pyrolysis [ORG CHEM] Thermal decomposition of acetone into ketene.

acetone number

acetone number [CHEM] A ratio used to estimate the degree of polymerization of
materials such as drying oils; it is the weight in grams of acetone added to 100
grams of a drying oil to cause an insoluble phase to form.

acetone glucose

acetone glucose See acetone sugar.

acetone cyanohydrin

acetone cyanohydrin [ORG CHEM] (CH3)2COHCN A colorless liquid obtained from con-
densation of acetone with hydrocyanic acid; used as an insecticide or as an organic
chemical intermediate.

acetolysis

acetolysis [ORG CHEM] Decomposition of an organic molecule through the action of
acetic acid or acetic anhydride.

acetone

acetone [ORG CHEM]CH3COCH3 A colorless, volatile, extremely flammable liquid, mis-
cible with water; used as a solvent and reagent. Also known as 2-propanone.

acetol

acetol [ORG CHEM]CH3COCH2OH A colorless liquid soluble in water; a reducing agent.

acetoin

acetoin [ORG CHEM]CH3COCHOHCH3 A slightly yellow liquid, melting point 15 C,
used as an aroma carrier in the preparation of flavors and essences; produced by
fermentation or fromdiacetyl by partial reduction with zinc and acid.

acetoamidoacetic acid

acetoamidoacetic acid See aceturic acid.

acetoacetic ester

acetoacetic ester See ethyl acetoacetate.

acetoacetic acid

acetoacetic acid [ORG CHEM]CH3COCH2COOH A colorless liquid miscible with water;
derived from -hydroxybutyric acid in the body.

acetoacetate

acetoacetate [ORG CHEM] A salt which contains the CH3COCH2COO radical; derived
from acetoacetic acid.

acetin

acetin [ORG CHEM]C3H5(OH)2OOCCH3 A thick, colorless, hygroscopic liquid with a
boiling point of 158 C, made by heating glycerol and strong acetic acid; soluble in
water and alcohol; used in tanning, as a dye solvent and food additive, and in
explosives. Also spelled acetine.

acetine

acetine See acetin.

acetidin

acetidin See ethyl acetate.

acetic ether

acetic ether See ethyl acetate.

acetic ester

acetic ester See ethyl acetate.

acetic anhydride

acetic anhydride [ORG CHEM] (CH3CO)2O A liquid with a pungent odor that combines

with water to form acetic acid; used as an acetylating agent.

acetic acid [ORG CHEM]CH3COOH 1. A clear, colorless liquid or crystalline mass with

a pungent odor, miscible with water or alcohol; crystallizes in deliquescent needles;

a component of vinegar. Also known as ethanoic acid. 2. A mixture of the normal

and acetic salts; used as a mordant in the dyeing of wool.

acetenyl

acetenyl See ethinyl.

acetate of lime

acetate of lime [ORG CHEM] Calcium acetate made from pyroligneous acid and a water

suspension of calcium hydroxide.

acetate dye

acetate dye [CHEM] 1. Any of a group of water-insoluble azo or anthroquinone dyes

used for dyeing acetate fibers. 2. Any of a group of water-insoluble amino azo dyes

that are treated with formaldehyde and bisulfate to make them water-soluble.

acetate

acetate [ORG CHEM] One of two species derived from acetic acid, CH3COOH; one type

is the acetate ion, CH3COO ; the second type is a compound whose structure contains

the acetate ion, such as ethyl acetate

acetanilide

acetanilide [ORG CHEM] An odorless compound in the formof white, shining, crystalline

leaflets or a white, crystalline powder with a melting point of 114–116 C; soluble in

hot water, alcohol, ether, chloroform, acetone, glycerol, and benzene; used as a

rubber accelerator, in the manufacture of dyestuffs and intermediates, as a precursor

in penicillin manufacture, and as a painkiller.

acetaminophen

acetaminophen [ORG CHEM]C8H9O2N Large monoclinic prisms with a melting point

of 169–170 C; soluble in organic solvents such as methanol and ethanol; used in

the manufacture of azo dyes and photographic chemicals, and as an analgesic and

antipyretic.

acetamidine hydrochloride

acetamidine hydrochloride [ORG CHEM]C2H6N2 HCl Deliquescent crystals that are

long prisms with a melting point reported as either 174 Cor164–166 C; soluble in

water and alcohol; used in the synthesis of imidazoles, pyrimidines, and triazines.

acetamide

acetamide [ORG CHEM]CH3CONH2 The crystalline, colorless amide of acetic acid, used

in organic synthesis and as a solvent.

acetal resins

acetal resins [ORG CHEM] Linear, synthetic resins produced by the polymerization of

formaldehyde (acetal homopolymers) or of formaldehyde with trioxane (acetal copol-

ymers); hard, tough plastics used as substitutes formetals. Also known as polyacet-

als.

acetaldehyde

acetaldehyde cyanohydrin See lactonitrile.

acetaldehyde

acetaldehyde [ORG CHEM]C2H4O A colorless, flammable liquid used chiefly to manu-

facture acetic acid.

acephatemet

acephatemet [ORG CHEM]CH3OCH3SPONH2 A white, crystalline solid with a melting

point of 39–41 C; limited solubility in water; used as an insecticide to control

cutworms and borers on vegetables.

acetal

acetal [ORG CHEM] 1. CH3CH(OC2H5)2 A colorless, flammable, volatile liquid used as

a solvent and in manufacture of perfumes. Also known as 1,1-diethoxyethane.

2. Any one of a class of compounds formed by the addition of alcohols to aldehydes.

acephate

acephate [ORG CHEM]C4H10NO3PS A white solid with a melting point of 72–80 C; very

soluble in water; used as an insecticide for a wide range of aphids and foliage pests.

acenocoumarol

acenocoumarol [ORG CHEM]C19H15NO6 A tasteless, odorless, white, crystalline powder

with a melting point of 197 C; slightly soluble in water and organic solvents; used

as an anticoagulant. Also known as acenocoumarin.

acenocoumarin

acenocoumarin See acenocoumarol.

acene

acene [ORG CHEM] Any condensed polycyclic compound with fused rings in a linear

arrangement; for example, anthracene.

acenaphthequinone

acenaphthequinone [ORG CHEM]C10H6(CO)2 A three-ring hydrocarbon in the form of

acetic ester

yellow needles melting at 261–263 C; insoluble in water and soluble in alcohol; used

in dye synthesis.

acenaphthene

acenaphthene [ORG CHEM]C12H10 An unsaturated hydrocarbon whose colorless crys-

tals melt at 92 C; insoluble in water; used as a dye intermediate and as an agent

for inducing polyploidy.

accessory element

accessory element See trace element.

acceptor

acceptor [CHEM] 1. A chemical whose reaction rate with another chemical increases

because the other substance undergoes another reaction.

 2. A species that acceptselectrons, protons, electron pairs, or molecules such as dyes.

accelofilter

accelofilter [CHEM] A filtration device that uses a vacuum or pressure to draw or force

the liquid through the filter to increase the rate of filtration.

accelerator mass spectrometer

accelerator mass spectrometer [SPECT] A combination of a mass spectrometer and

an accelerator that can be used to measure the natural abundances of very rare

radioactive isotopes.

acaroid resin

acaroid resin [ORG CHEM] A gum resin from aloelike trees of the genus Xanthorrhoea in

Australia and Tasmania; used in varnishes and inks. Also known as gum accroides;

yacca gum. { a kə ro ˙ id rez ən}

Ac

Ac See actinium.

abstraction reaction

abstraction reaction [CHEM] A bimolecular chemical reaction in which an atom that

is either neutral or charged is removed from a molecular entity. { ab strak shən

re ¯ ak shən}

absorptivity

absorptivity [ANALY CHEM] The constant a in the Beer’s law relation A abc, where A

is the absorbance, b the path length, and c the concentration of solution. Also known

as absorptive power. Formerly known as absorbency index; absorption constant;

extinction coefficient. { əb so ˙ rp tiv əd e ¯ }

absorptive power

absorptive power See absorptivity. { əb so ˙ rp tiv pau ˙ ər}

absorption tube

absorption tube [CHEM] A tube filled with a solid absorbent and used to absorb gases

and vapors. { əb so ˙ rp shən tu ¨ b}

absorption spectrum

absorption spectrum [SPECT] A plot of how much radiation a sample absorbs over a

range of wavelengths; the spectrum can be a plot of either absorbance or transmit-

tance versus wavelength, frequency, or wavenumber. { əb so ˙ rp shən spek trəm}

absorption spectroscopy

absorption spectroscopy [SPECT] An instrumental technique for determining the con-

centration and structure of a substance bymeasuring the intensity of electromagnetic

radiation it absorbs at various wavelengths. { əb so ˙ rp shən spek tra ¨s kə pe

absorption spectrophotometer

absorption spectrophotometer [SPECT] An instrument used to measure the relative

intensity of absorption spectral lines and bands. Also known as difference spectro-

photometer. { əb so ˙ rp shən spek trə fə ta ¨m ə dər}

absorption peak

absorption peak [SPECT] A wavelength of maximum electromagnetic absorption by

a chemical sample; used to identify specific elements, radicals, or compounds.

{ əb so ˙ rp shən pe ¯ k}

absorption line

absorption line [SPECT] A minute range of wavelength or frequency in the electromag-

netic spectrum within which radiant energy is absorbed by the medium through

which it is passing. { əb so ˙ rp shən lı ¯n}

absorption limit

absorption limit See absorption edge. { əb so ˙ rp shən lim ət}

absorption edge

absorption edge [SPECT] The wavelength corresponding to a discontinuity in the varia-

tion of the absorption coefficient of a substance with the wavelength of the radiation.

Also known as absorption limit. { əb so ˙ rp shən ej }

absorption constant

absorption constant See absorptivity. { əb so ˙ rp shən ka ¨ns tənt }

absorption

absorption [CHEM] The taking up of matter in bulk by other matter, as in dissolving

of a gas by a liquid. { əb so ˙ rp shən}

absorptiometric analysis

absorptiometric analysis [ANALY CHEM] Chemical analysis of a gas or a liquid by meas-

urement of the peak electromagnetic absorption wavelengths that are unique to a

specific material or element. { əb so ˙ rp te ¯ ə met rik ə nal ə sis }

absorptiometer

absorptiometer [ANALY CHEM] 1. An instrument equipped with a filter system or other

simple dispersing system to measure the absorption of nearly monochromatic radia-

tion in the visible range by a gas or a liquid, and so determine the concentration

of the absorbing constituents in the gas or liquid. 2. A device for regulating the

thickness of a liquid in spectrophotometry. { əb so ˙ rp te ¯ a ¨ məd ər}

absorbency index

absorbency index See absorptivity.

absorbency

absorbency [CHEM] Penetration of one substance into another.

absorbance

absorbance [PHYS CHEM] The common logarithmof the reciprocal of the transmittance

of a pure solvent.

absorbancy

absorbancy See absorbance.

absorb

absorb [CHEM] To take up a substance in bulk.

absolute stereochemistry

absolute stereochemistry See absolute configuration.

absolute reaction rate

absolute reaction rate [PHYS CHEM] The rate of a chemical reaction as calculated by

means of the (statistical-mechanics) theory of absolute reaction rates.

absolutemethod

absolutemethod [ANALY CHEM] Amethod of chemical analysis that bases characteriza-

tion completely on standards defined in terms of physical properties.

absolute gravity

absolute gravity [CHEM] Density or specific gravity of a fluid reduced to standard

conditions; for example, with gases, to 760 mmHg pressure and 0 C temperature.

Also known as absolute density.

absolute detection limit

absolute detection limit [ANALY CHEM] The smallest amount of an element or com-

pound that is detectable in or on a given sample; expressed in terms of mass units

or numbers of atoms or molecules

absolute density

absolute density See absolute gravity.

absolute configuration

absolute configuration [ORG CHEM] The three-dimensional arrangement of substitu-

ents around a chiral center in a molecule. Also known as absolute stereochemistry.

absolute boiling point [

absolute boiling point [CHEM] The boiling point of a substance expressed in the unit

of an absolute temperature scale.

absolute alcohol

absolute alcohol [ORG CHEM] Ethyl alcohol that contains no more than 1% water.

Also known as anhydrous alcohol.

ABS

ABS See acrylonitrile butadiene styrene resin.

Abney mounting

Abney mounting [SPECT] A modification of the Rowland mounting in which only the

slit is moved to observe different parts of the spectrum.

abietic acid

abietic acid [ORG CHEM]C20H30O2 A tricyclic, crystalline acid obtained from rosin; used

in making esters for plasticizers.

ab initio computation

ab initio computation [PHYS CHEM] Computation of the geometry of a molecule solely

from a knowledge of its composition and molecular structure as derived from the

solution of the Schro ¨ dinger equation for the given molecule.

Abel tester

Abel tester [PHYS CHEM] A laboratory instrument used in testing the flash point of

kerosine and other volatile oils having flash points below 120 F (49 C); the oil is

contained in a closed cup which is heated by a fixed flame below and a movable

flame above.

Abegg’s rule

Abegg’s rule [CHEM] An empirical rule, holding for a large number of elements, that

the sum of the maximum positive and negative valencies of an element equals eight.

abalyn

abalyn [ORG CHEM] A liquid rosin that is a methyl ester of abietic acid; prepared by

treating rosin with methyl alcohol; used as a plasticizer

spectroscopy

spectroscopy—The branch of physics concerned with the produc-

tion, measurement, and interpretation of electromagnetic spectra arising from

either emission or absorption of radiant energy by various substances.

organic chemistry

organic chemistry—The study of the structure, preparation

properties, and reactions of carbon compounds.

physical chemistry

physical chemistry—The branch of chemistry that deals with

the interpretation of chemical phenomena and properties in terms of the

underlying physical processes, and with the development of techniques for

their investigation.

inorganic chemistry

inorganic chemistry—The branch of chemistry that deals

with reactions and properties of all chemical elements and their compounds,

excluding hydrocarbons but usually including carbides and other simple carbon

compounds (such as CO2, CO, and HCN).

chemistry

—The scientific study of the properties, composi-

tion, and structure of matter, the changes in structure and composition

of matter, and accompanying energy changes.

analytical chemistry

analytical chemistry The science of the characteriza

tion and measurement of chemicals; qualitative analysis is concerned

with the description of chemical composition in terms of elements,

compounds, or structural units, whereas quantitative analysis is con-

cerned with the measurement of amount.