In this site we focused on the the areas of science incluod analytical chemisty, general chemistry, inorganic chemistry, organic chemistry, physical chemistry, and spectroscopy.(Online Chemistry Dictionary )

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ammonia [INORGCHEM]NH3 A colorless gaseous alkaline compound that is very soluble
in water, has a characteristic pungent odor, is lighter than air, and is formed as a
result of the decomposition of most nitrogenous organic material; used as a fertilizer
and as a chemical intermediate.


ammonation [INORG CHEM] A reaction in which ammonia is added to other molecules
or ions by covalent bond formation utilizing the unshared pair of electrons on the
nitrogen atom, or through ion-dipole electrostatic interactions.


ammine [INORG CHEM] One of a group of complex compounds formed by coordination
of ammonia molecules with metal ions.


aminotriazole [ORG CHEM]C2H4N4 Crystals with a melting point of 159 C; soluble in
water, methanol, chloroform, and ethanol; used as an herbicide, cotton plant defoli-
ant, and growth regulator for annual grasses and broadleaf and aquatic weeds.
Abbreviated ATA.


2-aminothiazole [ORG CHEM]C3H4N2S Pale-yellow crystals that melt at 92 C; soluble
in cold water, slightly soluble in ethyl alcohol; used as an intermediate in the
synthesis of sulfathiazole.

amino resin

amino resin [ORG CHEM] A type of resin prepared by condensation polymerization,
with an aldehyde, of a compound containing an amino group.

beta aminopyridine

beta aminopyridine [ORG CHEM]C5H6N2 Crystals with a melting point of 64 C; soluble in
water, alcohol, and benzene; used in drug and dye manufacture. Also known as


4-aminopyridine [ORG CHEM]C5H6N2 White crystals with a melting point of 158.9 C;
soluble in water; used as a repellent for birds. Abbreviated 4-AP.


para-aminophenol [ORG CHEM] p-HOC6H4NO2 A phenol in which an amino ( NH2)
group is located on the benzene ring of carbon atoms para (p) to the hydroxyl ( OH)
group; used as a photographic developer and as an intermediate in dye manufacture


aminophenol [ORG CHEM] A type of compound containing the NH2 and OH groups
joined to the benzene ring; examples are para-aminophenol and ortho-hydroxylaniline.

amino nitrogen

amino nitrogen [CHEM] Nitrogen combined with hydrogen in the amino group. Also
known as ammonia nitrogen.

3-amino-2-naphthoic acid

3-amino-2-naphthoic acid [ORG CHEM]H2NC10H6COOH Yellow crystals in the shape
of scales with a melting point of 214 C; soluble in alcohol and ether; used in the
determination of copper, nickel, and cobalt.


2-amino-2-methyl-1,3-propanediol [ORG CHEM] HOCH2C(CH3)(NH2)CH2OH Crystals
with amelting point of 109–111 C; soluble in water and alcohol; used in the synthesis
of surface-active agents, pharmaceuticals, and vulcanizers, and as an emulsifying
agent for cosmetics, leather dressings, polishes, and cleaning compounds.

amino group

amino group [ORG CHEM] A functional group ( NH2) formed by the loss of a hydrogen
atom from ammonia. 

3-amino-2,5-dichlorobenzoic acid

3-amino-2,5-dichlorobenzoic acid [ORG CHEM]C7H5O2NCl2 A white solid with a melt-
ing point of 200–201 C; solubility in water is 700 parts per million at 20 C; used as
a preemergence herbicide for soybeans, corn, and sweet potatoes.


aminodiborane [INORG CHEM] Any compound derived from diborane (B2H6) in which
one H of the bridge has been replaced by NH2.


aminocarb [ORG CHEM]C11H16N2O2 A tan, crystalline compound with a melting point
of 93–94 C; slightly soluble in water; used as an insecticide for control of forest
insects and pests of cotton, tomatoes, tobacco, and fruit crops.

gama - aminobutyric acid

gama - aminobutyric acid [ORG CHEM]H2NCH2CH2CH2COOH Crystals which are either leaf-
lets or needles, with a melting point of 202 C; thought to be a central nervous system
postsynaptic inhibitory transmitter. Abbreviated GABA.

E - aminocaproic acid

E - aminocaproic acid [ORG CHEM]C6H13NO2 Crystals with amelting point of 204–206 C;
freely soluble in water; used as an antifibrinolytic agent and a spacer for affinity


2-amino-1-butanol [ORG CHEM]CH3CH2CH(NH2)CH2OH A liquid miscible with water,
soluble in alcohols; used in the synthesis of surface-active agents, vulcanizing acceler-
ators, and pharmaceuticals, and as an emulsifying agent for such products as cosmetic
creams and lotions.


1-aminoanthraquinone [ORG CHEM]C14H9NO2 Ruby-red crystals with a melting point
of 250 C; freely soluble in alcohol, benzene, chloroform, ether, glacial acetic acid,
and hydrochloric acid; used in the manufacture of dyes and pharmaceuticals.

amino , amin

amino-, amin- [CHEM] Having the property of a compound in which the group NH2 is
attached to a radical other than an acid radical. 



amine [ORG CHEM] One of a class of organic compounds which can be considered to
be derived from ammonia by replacement of one or more hydrogens by functional


amination [ORG CHEM] 1. The preparation of amines. 2. A process in which the amino
group ( NH2) is introduced into organic molecules.


amidol [ORG CHEM]C6H3(NH2)2OH HCl A grayish-white crystalline salt; soluble in
water, slightly soluble in alcohol; used as a developer in photography and as an
analytical reagent.


amido [ORG CHEM] Indicating the NH2 radical when it is present in a molecule with
the CO radical.

amide hydrolysis

amide hydrolysis [ORG CHEM] The cleavage of an amide into its constitutive acid and
amine fragments by a net addition of water.


amide [ORG CHEM] One of a class of organic compounds containing the CONH2 radical.


amidation [ORG CHEM] The process of forming an amide; for example, in the laboratory
benzyl reacts with methyl amine to form N-methylbenzamide.


amicron [PHYS CHEM] A particle having a size of 10 7
centimeter or less, which is a
size in a system of classification of particle sizes in colloid chemistry.

Ames test

Ames test [ANALY CHEM] A bioassay that uses a set of histidine auxotrophic mutants of
Salmonella typhimurium for detectingmutagenic and possibly carcinogenic compounds.


americium [CHEM] A chemical element, symbol Am, atomic number 95; the mass
number of the isotope with the longest half-life is 243.


ambident [ORG CHEM] A chemical species or molecule that possesses two alternative
reactive sites, either of which can bond in a reaction; examples include cyanate ions,
thiosulfate ions, oxime anions, and enolate ions. Also known as ambidentate.


Am See americium

aluminum sulfate

aluminum sulfate [INORG CHEM]Al2(SO4)3 18H2O A colorless salt in the form of mono-
clinic crystals that decompose in heat and are soluble in water; used in papermaking,
water purification, and tanning, and as a mordant in dyeing. Also known as alum.

aluminum stearate

aluminum stearate [ORG CHEM] Al(C17H35COO)3 An aluminum soap in the form of a
white powder that is insoluble in water and soluble in oils; used for waterproofing
fabrics and concrete and as a drier in paints and varnishes.

aluminum sodium sulfate

aluminum sodium sulfate [INORG CHEM] AlNa(SO4)2 12H2O Colorless crystals with an
astringent taste and a melting point of 61 C; soluble in water; used as a mordant
and for waterproofing textiles, as a food additive, and for matches, tanning, ceramics,
engraving, and water purification. Abbreviated SAS. Also known as porous alum;
soda alum; sodium aluminum sulfate.

aluminum soap

aluminum soap [ORG CHEM] Any of various salts of higher carboxylic acids and alumi-
num that are insoluble in water and soluble in oils; used in lubricating greases,
paints, varnishes, and waterproofing substances.

aluminum silicate

aluminum silicate [INORG CHEM]Al2(SiO3)3 A white solid that is insoluble in water;
used as a refractory in glassmaking.

aluminum palmitate

aluminum palmitate [ORG CHEM] Al(C16H31O2) H2O An aluminum soap used in water-
proofing fabrics, paper, and leather and as a drier in paints.

aluminum oxide

aluminum oxide [INORG CHEM]Al2O3 A compound in the form of a white powder or
colorless hexagonal crystals; melts at 2020 C; insoluble in water; used in aluminum
production, paper, spark plugs, absorbing gases, light bulbs, artificial gems, and
manufacture of abrasives, refractories, ceramics, and electrical insulators.

aluminum orthophosphate

aluminum orthophosphate [INORG CHEM] AlPO4 White crystals, melting above 1500 C;
insoluble in water, soluble in acids and bases; useful in ceramics, paints, pulp, and
paper. Also known as aluminum phosphate.

aluminum oleate

aluminum oleate [ORG CHEM] A soaplike compound of aluminum and oleic acid, used
in lubricating oils and greases to improve their viscosity.

aluminum nitrate

aluminum nitrate [INORG CHEM] Al(NO3)3 9H2O White, deliquescent crystals with a melting point of 73 C; soluble in alcohol and acetone; used as a mordant for textiles,
in leather tanning, and as a catalyst in petroleum refining.

aluminum monostearate

aluminum monostearate [ORG CHEM] Al(OH)2[OOC(CH2)16CH3] A white to yellowish-
white powder with a melting point of 155 C; used in the manufacture of medicine,
paint, and ink, in waterproofing, and as a plastics stabilizer.

aluminum fluosilicate

aluminum fluosilicate [INORG CHEM]Al2(SiF6)3 A white powder that is soluble in hot
water; used for artificial gems, enamels, and glass. Also known as aluminum sili-

aluminum chloride

aluminum chloride [INORG CHEM] AlCl3 or Al2Cl6 A deliquescent compound in the form
of white to colorless hexagonal crystals; fumes in air and reacts explosively with
water; used as a catalyst.

aluminum borohydride

aluminum borohydride [ORG CHEM] Al(BH4)3 A volatile liquid with a boiling point of
44.5 C; used in organic synthesis and as a jet fuel additive.

aluminum acetate

aluminum acetate [ORG CHEM] Al(CH3COO)3 A white, amorphous powder that is solu-
ble in water; used in aqueous solution as an antiseptic.


aluminum [CHEM] A chemical element, symbol Al, atomic number 13, and atomic
weight 26.9815. Also spelled aluminium.


aluminosilicate [INORG CHEM] 3Al2O3 2SiO2 A colorless, crystalline combination of sili-
cate and aluminate in the form of rhombic crystals.


aluminon [ORG CHEM]C22H23N3O9 A yellowish-brown, glassy powder that is freely solu-
ble in water; used for the detection and colorimetric estimation of aluminum in
foods, water, and tissues, and as a pharyngeal aerosol spray.


alumina trihydrate

alumina trihydrate [INORG CHEM]Al2O3 3H2O, or Al(OH)3 A white powder; insoluble in
water, soluble in hydrochloric or sulfuric acid or sodium hydroxide; used in the
manufacture of ceramic glasses and in paper coating. Also known as aluminum
hydrate; aluminum hydroxide; hydrated alumina; hydrated aluminum oxide.


aluminate [INORG CHEM] A negative ion usually assigned the formula AlO2
and derived
from aluminum hydroxide.


alumina [INORG CHEM]Al2O3 The native formof aluminumoxide occurring as corundum
or in hydrated forms, as a powder or crystalline substance.


alum [INORG CHEM] 1. Any of a group of double sulfates of trivalent metals such as
aluminum, chromium, or iron and a univalent metal such as potassium or sodium.
2. See aluminumsulfate; ammoniumaluminumsulfate; potassiumaluminumsulfate.

alternation of multiplicities law

alternation of multiplicities law [CHEM] The law that the periodic table arranges the
elements in such a sequence that their number of orbital electrons, and hence their
multiplicities, alternates between even and odd numbers.

alternating copolymer

alternating copolymer [ORG CHEM] A polymer formed of two different monomer mole-
cules that alternate in sequence in the polymer chain.

alternant hydrocarbon

alternant hydrocarbon [ORG CHEM] A member of a class of conjugated molecules
whose carbon atoms can be divided into two sets so that members of one set are
formally bonded only to members of the other set.

alpha position

alpha position [ORG CHEM] In chemical nomenclature, the position of a substituting
group of atoms in the main group of a molecule; for example, in a straight-chain compound such as -hydroxypropionic acid (CH3CHOHCOOH), the hydroxyl radical
is in the alpha position.

alpha olefin

alpha olefin [ORG CHEM] An olefin where the unsaturation (double bond) is at the
alpha position, that is, between the two end carbons of the carbon chain.

alpha cellulose

alpha cellulose [ORG CHEM] A highly refined, insoluble cellulose from which sugars,
pectin, and other soluble materials have been removed. Also known as chemical


allyxycarb [ORG CHEM]C16H22N2O2 A yellow, crystalline compound used as an insecti-
cide for fruit orchards, vegetable crops, rice, and citrus


allylurea [ORG CHEM]C4H8N2O Crystals with a melting point of 85 C; freely soluble in
water and alcohol; used to manufacture allylthiourea and other corrosion inhibitors.


allyltrichlorosilane [ORG CHEM]CH2CHCH2SiCl3 A pungent, colorless liquid with a boil-
ing point of 117.5 C; used as an intermediate for silicones.


allylthiourea [ORG CHEM]C3H5NHCSNH2 A white, crystalline solid that melts at 78 C;
soluble in water; used as a corrosion inhibitor.

allyl sulfide

allyl sulfide [ORG CHEM] (CH2CHCH2)2S A colorless liquid with a garliclike odor and a
boiling point of 139 C; used in synthetic oil of garlic.

allyl resin

allyl resin [ORG CHEM] Any of a class of thermosetting synthetic resins derived from
esters of allyl alcohol or allyl chloride; used in making cast and laminated products.
Also known as allyl plastic.

allyl mercaptan

allyl mercaptan [ORG CHEM]CH2CHCH2SH A colorless liquid with a boiling point of
67–68 C; soluble in ether and alcohol; used as intermediate in pharmaceutical

allyl isothiocyanate

allyl isothiocyanate [ORG CHEM]CH2CH:CH2NCS A pungent, colorless to pale-yellow
liquid; soluble in alcohol, slightly soluble in water; irritating odor; boiling point
152 C; used as a fumigant and as a poison gas. Also known as mustard oil.

allylic substitution

allylic substitution [ORG CHEM] A reaction occurring at position 1 of an allylic system
(with the double bond between positions 2 and 3) in which the incoming group is
attached to the same atom (position 1) as the leaving group, or the incoming group
is attached at position 3, with the double bond moving from positions 2 and 3 to
positions 1 and 2.

allylic hydrogen

allylic hydrogen [ORG CHEM] In an organic molecule, a hydrogen attached to a carbon
atom that is adjacent to a double bond.


allylene [ORG CHEM]CH3C:CH An acetylenic, three-carbon hydrocarbon; a colorless
gas boiling at 24 C; soluble in ether.

allyl cyanide

allyl cyanide [ORG CHEM]C4H5N A liquid with an onionlike odor and a boiling point
of 119 C; slightly soluble in water; used as a cross-linking agent in polymerization.

allyl chloride

allyl chloride [ORG CHEM]CH2CHCH2Cl A volatile, pungent, toxic, flammable, colorless
liquid, boiling at 46 C; insoluble in water; made by chlorination of propylene at high

allyl cation

allyl cation [ORG CHEM] A carbonium cation with a structure usually represented as
+; attachment site is the saturated carbon atom.

allyl bromide

allyl bromide [ORG CHEM]C3H5Br A colorless to light yellow, irritating toxic liquid with
a boiling point of 71.3 C; soluble in organic solvents; used in organic synthesis and
for the manufacture of synthetic perfumes.



allylamine [ORG CHEM]CH2CHCH2NH2 A yellow oil that is miscible with water; boils
at 58 C; prepared from mustard oil.

allyl alcohol

allyl alcohol [ORG CHEM]CH2CHCH2OH Colorless, pungent liquid, boiling at 96 C;
soluble in water; made from allyl chloride by hydrolysis.

allyl alcohol

allyl alcohol [ORG CHEM]CH2CHCH2OH Colorless, pungent liquid, boiling at 96 C;
soluble in water; made from allyl chloride by hydrolysis.


allylacetone [ORG CHEM]CH2CHCH2CH2COCH3 A colorless liquid, soluble in water and organic solvents; used in pharmaceutical synthesis, perfumes, fungicides, and


allyl- [ORG CHEM] A prefix used in names of compounds whose structure contains an
allyl cation.


allulose [ORG CHEM]CH2OHCO(CHOH)3CH2OH A constituent of cane sugar molasses;
it is nonfermentable.



allotropy [CHEM] The assumption by an element of two or more different forms or
structures which are most frequently stable in different temperature ranges, such
as different crystalline forms of carbon as charcoal, graphite, or diamond. Also
known as allotriomorphism; allotropism.



allotrope [CHEM] A form of an element showing allotropy.


allo- [CHEM] Prefix applied to the stabler form of two isomers.


allidochlor [ORG CHEM]C8H12NOCl An amber liquid having slight solubility in water;
used as a preemergence herbicide for vegetable crops, soybeans, sorghum, and


allethrin [ORG CHEM] An insecticide, a synthetic pyrethroid, more effective than pyre-


allene [ORG CHEM]C3H4 An unsaturated aliphatic hydrocarbon with two double bonds.
Also known as propadiene.


allelochemistry [CHEM] The science of compounds synthesized by one organism that
stimulate or inhibit other organisms.


alkyne [ORG CHEM] One of a group of organic compounds containing a carbon-to-
carbon triple bond.

alkyl halide

alkyl halide [ORG CHEM] A compound consisting of an alkyl group and a halogen; an
example is ethylbromide.


alkylene [ORG CHEM] An organic radical formed froman unsaturated aliphatic hydrocar-
bon; for example, the ethylene radical C2H3 .


alkylation [ORG CHEM] A chemical process in which an alkyl radical is introduced into
an organic compound by substitution or addition.


alkylate [ORG CHEM] A product of the alkylation process in petroleum refining.


alkylamine [ORG CHEM] A compound consisting of an alkyl group attached to the
nitrogen of an amine; an example is ethylamine, C2H5NH2.


alkyl [ORG CHEM] An organic group that results from removal of a hydrogen atom from
an acyclic, saturated hydrocarbon; may be represented in a chemical formula by
R .

alkyd resin

alkyd resin [ORG CHEM] A class of adhesive resins made from unsaturated acids and


alkoxy [ORG CHEM] An alkyl radical attached to a molecule by oxygen, such as the
ethoxy radical.


alkene [ORG CHEM] One of a class of unsaturated aliphatic hydrocarbons containing
one or more carbon-to-carbon double bonds.


alkanolamine [ORG CHEM] One of a group of viscous, water-soluble amino alcohols of
the aliphatic series.


alkannin [ORG CHEM]C16H16O5 A red powder, the coloring ingredient of alkanet; soluble
in alcohol, benzene, ether, and oils; used as a coloring agent for fats and oils, wines,
and wax.


alkane [ORG CHEM] A member of a series of saturated aliphatic hydrocarbons having the empirical formula CnH2n+2. Also known as paraffin; paraffinic hydrocarbon.


alkamine [ORG CHEM] A compound that has both the alcohol and amino groups. Also
known as amino alcohol.


alkaloid [ORG CHEM] One of a group of nitrogenous bases of plant origin, such as
nicotine, cocaine, and morphine.


alkalinity [CHEM] The property of having excess hydroxide ions in solution.

alkaline earth metals

alkaline-earth metals [CHEM] The heaviest members of group 2 in the periodic table;
usually calcium, strontium, magnesium, and barium.

alkaline earth

alkaline earth [INORG CHEM] An oxide of an element of group 2 in the periodic table,
such as barium, calcium, and strontium. Also known as alkaline-earth oxide.


alkaline [CHEM] 1. Having properties of an alkali. 2. Having a pH greater than 7.


alkalimetry [ANALY CHEM] Quantitative measurement of the concentration of bases or
the quantity of one free base in a solution; techniques include titration and other
analytical methods.


alkalimeter [ANALY CHEM] 1. An apparatus for measuring the quantity of alkali in a
solid or liquid. 2. An apparatus for measuring the quantity of carbon dioxide formed
in a reaction.

alkali metal

alkali metal [CHEM] Any of the elements of group I in the periodic table: lithium,
sodium, potassium, rubidium, cesium, and francium.


alkalide [INORG CHEM] A member of a class of crystalline salts with an alkali metal

alkali blue

alkali blue [ORG CHEM] The sodium salt of triphenylrosanilinesulfonic acid; used as
an indicator.

alkali alcoholate

alkali alcoholate [ORG CHEM] A compound formed from an alcohol and an alkali metal
base; the alkali metal replaces the hydrogen in the hydroxyl group.

alkali-aggregate reaction

alkali-aggregate reaction [CHEM] The chemical reaction of an aggregate with the alkali
in a cement, resulting in a weakening of the concrete.


alkali [CHEM] Any compound having highly basic qualities.


alkalescence [CHEM] The property of a substance that is alkaline, that is, having a
pH greater than 7.


alizarin [ORG CHEM]C14H6O2(OH)2 An orange crystalline compound, insoluble in cold
water; made synthetically from anthraquinone; used in the manufacture of dyes and
red pigments.


aliquot [CHEM] A part of a sample that has been divided into exactly equal parts with
no remainder.


aliquant [CHEM] A part of a sample that has been divided into a set of equal parts
plus a smaller remainder part.

aliphatic series

aliphatic series [ORG CHEM] A series of open-chained carbon-hydrogen compounds;
the two major classes are the series with saturated bonds and with the unsaturated.

aliphatic polyene compound

aliphatic polyene compound [ORG CHEM] Any unsaturated aliphatic or alicyclic com-
pound with more than four carbons in the chain and with at least two double bonds;
for example, hexadiene.



aliphatic [ORG CHEM] Of or pertaining to any organic compound of hydrogen and carbon
characterized by a straight chain of the carbon atoms; three subgroups of such
compounds are alkanes, alkenes, and alkynes.


alicyclic [ORG CHEM] 1. Having the properties of both aliphatic and cyclic substances.
2. Referring to a class of saturated hydrocarbon compounds whose structures contain
one ring. Also known as cycloaliphatic; cycloalkane.Any one of the compounds of
the alicyclic class. Also known as cyclane.

alginic acid

alginic acid [ORG CHEM](C6H8O6)n An insoluble colloidal acid obtained from brown
marine algae; it is hard when dry and absorbent when moist. Also known as algin.

alfin catalyst

alfin catalyst [ORG CHEM] A catalyst derived from reaction of an alkali alcoholate with
an olefin halide; used to convert olefins (for example, ethylene, propylene, or butyl-
enes) into polyolefin polymers.


Aldrin [ORG CHEM]C12H8Cl6 Trade name for a water-insoluble, white, crystalline com-
pound, consisting mainly of chlorinated dimethanonaphthalene; used as a pesticide.


aldose [ORG CHEM] A class of monosaccharide sugars; the molecule contains an alde-
hyde group.

aldol condensation

aldol condensation [ORG CHEM] Formation of a -hydroxycarbonyl compound by the
condensation of an aldehyde or a ketone in the presence of an acid or base catalyst.
Also known as aldol reaction.


aldol [ORG CHEM]CH3CH(OH)CH2CHO A colorless, thick liquid with a boiling point of
83 C; used in manufacturing rubber age resistors, accelerators, and vulcanizers.


aldohexose [ORG CHEM] A hexose, such as glucose or mannose, containing the alde-
hyde group.


aldicarb [ORG CHEM]C7H14N2O2S A colorless, crystalline compound with a melting
point of 100 C; used as an insecticide, miticide, and nematicide to treat soil for
cotton, sugarbeets, potatoes, peanuts, and ornamentals.

aldehyde polymer

aldehyde polymer [ORG CHEM] Any of the plastics based on aldehydes, such as formal-
dehyde, acetaldehyde, butyraldehyde, or acrylic aldehyde (acrolein). 

aldehyde ammonia

aldehyde ammonia [ORG CHEM]CH3CHOHNH2 A white, crystalline solid with a melting
point of 97 C; soluble in water and alcohol; used in organic synthesis and as a
vulcanization accelerator.


aldehyde [ORG CHEM] One of a class of organic compounds containing the CHO radical.


alcosol [CHEM] Mixture of an alcohol and a colloid.


alcoholysis [ORG CHEM] The breaking of a carbon-to-carbon bond by addition of an



alcoholate [ORG CHEM] A compound formed by the reaction of an alcohol with an
alkali metal. Also known as alkoxide.


alcohol [ORG CHEM] Any member of a class of organic compounds in which a hydrogen
atom of a hydrocarbon has been replaced by a hydroxy ( OH) group.


alcogel [CHEM] A gel formed by an alcosol.


alchemy [CHEM] A speculative chemical systemhaving as its central aims the transmu-
tation of base metals to gold and the discovery of the philosopher’s stone.


alanyl [ORG CHEM] The radical CH3CHNH2CO ; occurs in, for example, alanyl alanine,
a dipeptide.


Al See aluminum.


ajmaline [ORG CHEM]C20H26N2O2 An amber, crystalline alkaloid obtained from Rauwolfia
plants, especially R.serpentina.

air slaked

air-slaked [CHEM] Having the property of a substance, such as lime, that has been at
least partially converted to a carbonate by exposure to air.

air line

air line [SPECT] Lines in a spectrum due to the excitation of air molecules by spark
discharges, and not ordinarily present in arc discharges.

air fuel ratio

air-fuel ratio [CHEM] The ratio of air to fuel by weight or volume which is significant
for proper oxidative combustion of the fuel.

air deficiency

air deficiency [CHEM] Insufficient air in an air-fuel mixture causing either incomplete
fuel oxidation or lack of ignition.


air [CHEM] A predominantlymechanicalmixture of a variety of individual gases forming
the earth’s enveloping atmosphere.


agostic [ORG CHEM] A three-center, two-electron bonding interaction in which a hydro-
gen atom is bonded to both a carbon atom and a metal atom, such as the interaction
of a CH bond and an unsaturated transition-metal compound.


aging [CHEM] All irreversible structural changes that occur in a precipitate after it has


aggregation [CHEM] A process that results in the formation of aggregates.


aggregate [CHEM] A group of atoms or molecules that are held together in any way,
for example, a micelle.


agavose [ORG CHEM]C12H22O11 A sugar found in the juice of the agave tree; used in
medicine as a diuretic and laxative.

agaric acid

agaric acid [ORG CHEM]C19H36(OH)(COOH)3 An acid with melting point 141 C; soluble
in water, insoluble in benzene; used as an irritant. Also known as agaricin.

affinity chromatography

affinity chromatography [ANALY CHEM] A chromatographic technique that utilizes the
ability of biological molecules to bend to certain ligands specifically and reversibly;
used in protein biochemistry.


affinity [CHEM] The extent to which a substance or functional group can enter into a
chemical reactionwith a given agent. Also known as chemical affinity.


AES See Auger electron spectroscopy


aerosol [CHEM] A suspension of small particles in a gas; the particles may be solid
or liquid or a mixture of both; aerosols are formed by the conversion of gases to
particles, the disintegration of liquids or solids, or the suspension of powdered


aerogel [CHEM] A porous solid formed from a gel by replacing the liquid with a gas
with little change in volume so that the solid is highly porous.

aeration cell

aeration cell [PHYS CHEM] An electrolytic cell whose electromotive force is due to
electrodes of the same material located in different concentrations of dissolved air.
Also known as oxygen cell.

adsorption potential

adsorption potential [PHYS CHEM] A change in the chemical potential that occurs as
an ionmoves froma gas or solution phase to the surface of an adsorbent.

adsorption isotherm

adsorption isotherm [PHYS CHEM] The relationship between the gas pressure p and
the amount w, in grams, of a gas or vapor taken up per gram of solid at a constant

adsorption isobar

adsorption isobar [PHYS CHEM] A graph showing how adsorption varies with some
parameter, such as temperature, while holding pressure constant.

adsorption indicator

adsorption indicator [ANALY CHEM] An indicator used in solutions to detect slight
excess of a substance or ion; precipitate becomes colored when the indicator is
adsorbed. An example is fluorescein.

adsorption complex

adsorption complex [CHEM] An entity consisting of an adsorbate and that portion of
the adsorbent to which it is bound.

adsorption chromatography

adsorption chromatography [ANALY CHEM] Separation of a chemical mixture (gas or
liquid) by passing it over an adsorbent bed which adsorbs different compounds at
different rates


adsorption [CHEM] The surface retention of solid, liquid, or gas molecules, atoms, or
ions by a solid or liquid, as opposed to absorbtion, the penetration of substances
into the bulk of the solid or liquid.


adsorbent [CHEM] A solid or liquid that adsorbs other substances; for example, char-
coal, silica, metals, water, and mercury.


adsorbate [CHEM] A solid, liquid, or gas which is adsorbed as molecules, atoms, or
ions by such substances as charcoal, silica,metals, water, andmercury.


adiponitrile [ORG CHEM] NC(CH2)4CN The high-boiling liquid dinitrile of adipic acid;
used to make nylon intermediates.

adipic acid

adipic acid [ORG CHEM] HOOC(CH2)4COOH A colorless crystalline dicarboxylic acid,
sparingly soluble in water; used in nylon manufacture.


adipate [ORG CHEM] Salt produced by reaction of adipic acid with a basic compound.

adiabatic flame temperature

adiabatic flame temperature [PHYS CHEM] The highest possible temperature of com-
bustion obtained under the conditions that the burning occurs in an adiabatic vessel,
that it is complete, and that dissociation does not occur.


adduct [CHEM] 1. A chemical compound that forms from chemical addition of two
species; for example, reaction of butadiene with styrene forms an adduct, 4-phenyl-
1-cyclohexene. 2. The complex compound formed by association of an inclusion

addition reaction

addition reaction [ORG CHEM] A type of reaction of unsaturated hydrocarbons with
hydrogen, halogens, halogen acids, and other reagents, so that no change in valency
is observed and the organic compound forms a more complex one.

addition polymerization

addition polymerization [ORG CHEM] A reaction initiated by an anion, cation, or radical
in which a large number of monomer units are added rapidly (a chain reaction) until
terminated by some mechanism, forming a high-molecular-weight polymer in a very
short time; an example is the free-radical polymerization of propylene to polypro-

addition polymer

addition polymer [ORG CHEM] A polymer formed by the chain addition of unsaturated
monomer molecules, such as olefins, with one another without the formation of a
by-product, as water; examples are polyethylene, polypropylene, and polystyrene.
Also known as addition resin.

addition agent

addition agent [PHYS CHEM] A substance added to a plating solution to change charac-
teristics of the deposited substances.


adatom [PHYS CHEM] An atom adsorbed on a surface so that it will migrate over the



adamsite [ORG CHEM]C6H4 NH C6H4 AsCl A yellowcrystalline arsenical; used in leather
tanning and in warfare and riot control to produce skin and eye irritation, chest
distress, and nausea; U.S. Army code is DM. Also known as diphenylaminechloroar-
sine; phenarsazine chloride.


adamantane [ORG CHEM]AC10H16 alicyclic hydrocarbon whose structure has the same
arrangement of carbon atoms as does the basic unit of the diamond lattice.

acyloin condensation

acyloin condensation [ORG CHEM] The reaction of an aliphatic ester with metallic
sodium to form intermediates converted by hydrolysis into aliphatic -hydroxy-
ketones called acyloins.


acyloin [ORG CHEM] An organic compound that may be synthesized by condensation
of aldehydes; an example is benzoin, C6H5COCHOHC6H5.


acylnitrene [ORG CHEM] A nitrene in which the nitrogen is covalently bonded to an
acyl group.

acyl halide

acyl halide [ORG CHEM] One of a large group of organic substances containing the
halocarbonyl group; for example, acyl fluoride.


acylcarbene [ORG CHEM] A carbene radical in which at least one of the groups attached
to the divalent carbon is an acyl group; for example, acetylcarbene.


acylation [ORG CHEM] Any process whereby the acyl group is incorporated into a mole-
cule by substitution.


acyl [ORG CHEM] A radical formed from an organic acid by removal of a hydroxyl group;
the general formula is RCO, where Rmay be aliphatic, alicyclic, or aromatic.

acyclic compound

acyclic compound [ORG CHEM] A chemical compound with an open-chain molecular
structure rather than a ring-shaped structure; for example, the alkane series.

activity series

activity series [CHEM] A series of elements that have similar properties—for example,
metals—arranged in descending order of chemical activity.

activity coefficient

activity coefficient [PHYS CHEM] A characteristic of a quantity expressing the deviation
of a solution from ideal thermodynamic behavior; often used in connection with


activity [PHYS CHEM] A thermodynamic function that correlates changes in the chemical
potential with changes in experimentally measurable quantities, such as concentra-
tions or partial pressures, through relations formally equivalent to those for ideal

active solid

active solid [CHEM] A porous solid possessing adsorptive properties and used for
chromatographic separations.

active site

active site [CHEM] The effective site at which a given heterogeneous catalytic reaction
can take place. Also known as active center.

active center

active center [CHEM] 1. Any one of the points on the surface of a catalyst at which
the chemical reaction is initiated or takes place. 2. See active site.


activator [CHEM] 1. A substance that increases the effectiveness of a rubber vulcaniza-
tion accelerator; for example, zinc oxide or litharge. 2. A trace quantity of a substance
that imparts luminescence to crystals; for example, silver or copper in zinc sulfide
or cadmium sulfide pigments.

activation energy

activation energy [PHYS CHEM] The energy, in excess over the ground state, which must
be added to an atomic or molecular system to allow a particular process to take


activation [CHEM] Treatment of a substance by heat, radiation, or activating reagent
to produce a more complete or rapid chemical or physical change.

activated complex

activated complex [PHYS CHEM] An energetically excited state which is intermediate
between reactants and products in a chemical reaction. Also known as transition