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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atomic fluorescence spectroscopy

atomic fluorescence spectroscopy [SPECT] A form of atomic spectroscopy in which
the sample atoms are first excited by absorbing radiation from an external source
containing the element to be detected, and the intensity of radiation emitted at
characteristic wavelengths during transitions of these atoms back to the ground
state is observed. { ə¦ta¨m ik flu˙ ¦res əns spek tra¨s kə pe¯ }

atomic emission spectroscopy [SPECT] A form of atomic spectroscopy in which one
observes the emission of light at discrete wavelengths by atoms which have been
electronically excited by collisions with other atoms and molecules in a hot gas.
{ ə¦ta¨m ik ə¦mish ən spek tra¨s kə pe¯ }

atomic absorption spectroscopy

atomic absorption spectroscopy [SPECT] An instrumental technique for detecting concentrations
of atoms to parts per million by measuring the amount of light absorbed
by atoms or ions vaporized in a flame or an electrical furnace. { ə¦ta¨ mik əb¦so¨ rp
shən spek tra¨s kə pe¯ }

atom cluster

atom cluster [PHYS CHEM] An assembly of between three and a few thousand atoms
or molecules that are weakly bound together and have properties intermediate
between those of the isolated atom or molecule and the bulk or solid-state material.
{ ad əm kləs tər }


atom [CHEM] The individual structure which constitutes the basic unit of any chemical
element. { ad əm }


atactic [ORG CHEM] Of the configuration for a polymer, having the opposite steric
configurations for the carbon atoms of the polymer chain occur in equal frequency
and more or less at random. { a¯ tak tik }

asymmetry effect

asymmetry effect [PHYS CHEM] The asymmetrical distribution of the ion cloud around
an ion that results from the finite relaxation time for the ion cloud when a voltage
is applied; leads to a reduction in ion mobility. { a¯ sim ə tre¯ i fekt }


asymmetry [PHYSCHEM] The geometrical design of a molecule, atom, or ion that cannot
be divided into like portions by one or more hypothetical planes. Also known as
molecular asymmetry. { ¦a¯ sim ə trə }

asymmetric synthesis

asymmetric synthesis [ORG CHEM] Chemical synthesis of a pure enantiomer, or of an
enantiomorphic mixture in which one enantiomer predominates, without the use of
resolution. { ¦a¯ sə¦me trik sin thə səs }

asymmetric carbon atom

asymmetric carbon atom [ORG CHEM] A carbon atom with four different atoms or groups of atoms bonded to it. Also known as chiral carbon atom; stereogenic center. { ¦a¯ sə¦me trik ¦ka¨ r bən ad əm }

astronomical spectroscopy

astronomical spectroscopy [SPECT] The use of spectrographs in conjunction with telescopes
to obtain observational data on the velocities and physical conditions of
astronomical objects. { as trə na¨m ə kəl spek tra¨s kə pe¯ }


astatine [CHEM] A radioactive chemical element, symbol At, atomic number 85, the
heaviest of the halogen elements. { as tə te¯n }


Astage [ORG CHEM] An early stage in a thermosetting resin reaction characterized by
linear structure, solubility, and fusibility of the material. { a¯ sta¯j }

assay [ANALY CHEM] Qualitative or quantitative determination of the components of
a material, as an ore or a drug. { a sa¯ }


aspartame [ORG CHEM] C14H18N2O5 A dipeptide ester about 160 times sweeter than
sucrose in aqueous solution; used as a low-calorie sweetener. { a spa¨ r ta¯m }


ashing [ANALY CHEM] An analytical process in which the chemical material being analyzed
is oven-heated to leave only noncombustible ash. { ash iŋ }


ash [CHEM] The incombustible matter remaining after a substance has been incinerated.
{ ash }

ascending chromatography

ascending chromatography [ANALY CHEM] A technique for the analysis of mixtures of
two or more compounds in which the mobile phase (sample and carrier) rises through
the fixed phase. { ə send iŋ kro¯ mə ta¨g rə fe¯ }


asarone [ORG CHEM] C12H16O3 A crystalline substance with melting point 67 C; insoluble
in water, soluble in alcohol; found in plants of the genus Asarum; used as a
constituent in essential oils such as calumus oil. { as ə ro¯n }


aryne [ORG CHEM] An aromatic species in which two adjacent atoms of a ring lack
substituents, with two orbitals each missing an electron. Also known as benzyne.
{ a rı¯n }

aryloxy compound

aryloxy compound [ORG CHEM] One of a group of compounds useful as organic weed
killers, such as 2,4-dichlorophenoxyacetic acid (2,4-D). { ¦ar əl¦a¨ k se¯ ka¨m pau˙ nd }


arylide [ORG CHEM] A compound formed from a metal and an aryl group, for example,
PbR4, where R is the aryl group. { ar ə lı¯d }


arylene [ORG CHEM] A radical that is bivalent and formed by removal of hydrogen from
two carbon sites on an aromatic nucleus. { ar ə le¯n }


aryl diazo compound

aryl diazo compound [ORG CHEM] A diazo compound bonded to the ring structure
characteristic of benzene or any other aromatic derivative. { arəl dı¯a¯ zo¯
ka¨mpau˙ nd }

aryl compound

aryl compound [ORG CHEM] Molecules with the six-carbon aromatic ring structure
characteristic of benzene or compounds derived from aromatics. { arəl
ka¨mpau˙ nd }


arylamine [ORG CHEM] An organic compound formed from an aromatic hydrocarbon
that has at least one amine group joined to it, such as aniline. { arələme¯n }


arsonium [INORG CHEM] AsH4 A radical which may be considered analogous to the
ammonium radical in that a compound such as AsH4OH may form. { a¨ rso¯ ne¯ əm }

arsonic acid

arsonic acid [INORG CHEM] An acid derived from orthoarsenic acid, OAs(OH)3; the type
formula is generally considered to be RAsO(OH)2; an example is para-aminobenzenearsonic
acid, NH2C6H4AsO(OH)2. {a¨ r¦sa¨nik asəd }

arsinic acid

arsinic acid [INORG CHEM] An acid of general formula R2AsO2H; derived from trivalent
arsenic; an example is cacodylic acid, or dimethylarsinic acid, (CH3)2AsO2H. { a¨ r¦sin
ik asəd }

arseno compound

arseno compound [ORGCHEM] A compound containing an As-As bond with the general
formula (RAs)n, where R represents a functional group; structures are cyclic or longchain
polymers. { a¨ rs ən o¯ ka¨m pau˙ nd }


arsenobenzene [ORG CHEM] C6H5As:AsC6H5 White needles that melt at 212 C; insoluble
in cold water, soluble in benzene; derivatives have some use in medicine. { a¨ rs
ən o¯ ben ze¯n }


arsenite [INORG CHEM] 1. AsO3-3 A negative ion derived from aqueous solutions of
As4O6. 2. A salt or ester of arsenious acid. { a¨ r sə nı¯t }

arseno compound

arseno compound [ORGCHEM] A compound containing an As-As bond with the general
formula (RAs)n, where R represents a functional group; structures are cyclic or longchain
polymers. { a¨ rs ən o¯ ka¨m pau˙ nd }


arsenobenzene [ORG CHEM] C6H5As:AsC6H5 White needles that melt at 212 C; insoluble
in cold water, soluble in benzene; derivatives have some use in medicine. { a¨ rs
ən o¯ ben ze¯n }


arsenite [INORG CHEM] 1. AsO3-3 A negative ion derived from aqueous solutions of
As4O6. 2. A salt or ester of arsenious acid. { a¨ r sə nı¯t }


arsenin [ORG CHEM] A heterocyclic organic compound composed of a six-membered
ring system in which the carbon atoms are unsaturated and the unique heteroatom
is arsenic, with no nitrogen atoms present. { a¨ r sen ən }


arsenide [CHEM] A binary compound of negative, trivalent arsenic; for example, H3As
or GaAs. { a¨ rs ən ı¯d }

arsenic trisulfide

arsenic trisulfide [INORG CHEM] As2S3 An acidic compound in the form of yellow or
red monoclinic crystals with a melting point at 300 C; occurs as the mineral orpiment;
used as a pigment. { a¨ rs ən ik tri səl fı¯d }

arsenic trioxide

arsenic trioxide [INORG CHEM] As2O3 A toxic compound, slightly soluble in water; octahedral
crystals change to the monoclinic form by heating at 200 C; occurs naturally
as arsenolite and claudetite; used in small quantities in some medicinal preparations.
Also known as arsenic oxide; arsenious acid. { a¨ rs ən ik tri a¨ k sı¯d }

arsenic trichloride

arsenic trichloride [INORG CHEM] AsCl3 An oily, colorless liquid that dissolves in water;
used in ceramics, organic chemical syntheses, and in the preparation of pharmaceuticals.
{ a¨ rs ən ik tri klo˙ r ı¯d }

arsenic pentoxide

arsenic pentoxide [INORG CHEM] As2
O5 A white, deliquescent compound that decomposes
by heat and is soluble in water. Also known as arsenic oxide. { a¨ rs ən
ik pent a¨ k sı¯d }

arsenic pentasulfide

arsenic pentasulfide [INORG CHEM] As2
S5 Yellow crystals that are insoluble in water
and readily decompose to the trisulfide and sulfur; used as a pigment. { a¨ rs ən
ik pent ə səl fı¯d }

arsenic disulfide

arsenic disulfide [INORG CHEM] As2
S2 Red, orange, or black monoclinic crystals, insoluble
in water; used in fireworks; occurs naturally as realgar. { a¨ rs ən ik dı¯ səl fı¯d }

arsenic acid

arsenic acid [INORG CHEM] H3AsO41/2H2O White, poisonous crystals, soluble in water
and alcohol; used in manufacturing insecticides, glass, and arsenates and as a
defoliant. Also known as orthoarsenic acid. { a¨ rsenik asəd }


arsenic [CHEM] A chemical element, symbol As, atomic number 33, atomic weight
74.9216. { a¨ rsənik }


arsenate [INORG CHEM] 1. AsO4
3 A negative ion derived from orthoarsenic acid,
H3AsO41/2H2O. 2. A salt or ester of arsenic acid. { a¨ rsəna¯t }

Arrhenius equation

Arrhenius equation [PHYS CHEM] The relationship that the specific reaction rate constant
k equals the frequency factor constant s times exp (Hact /RT), where Hact
is the heat of activation, R the gas constant, and T the absolute temperature. { arra¯ 
ne¯ əs ikwa¯ zhən }

aromatic nucleus

aromatic nucleus [ORG CHEM] The six-carbon ring characteristic of benzene and related
series, or condensed six-carbon rings of naphthalene, anthracene, and so forth.
{ ¦ar ə¦mad ik nu¨ kle¯ əs }

aromatic hydrocarbon

aromatic hydrocarbon [ORG CHEM] A member of the class of hydrocarbons, of which
benzene is the first member, consisting of assemblages of cyclic conjugated carbon
atoms and characterized by large resonance energies. Also known as arene. { ¦ar
ə¦mad ik ¦hı¯ drə ka¨ r bən }


aromatic alcohol

aromatic alcohol [ORG CHEM] Any of the compounds containing the hydroxyl group
in a side chain to a benzene ring, such as benzyl alcohol. { ¦ar ə¦mad ik al kə ho˙ l }


aromatic [ORG CHEM] 1. Pertaining to or characterized by the presence of at least
one benzene ring. 2. Describing those compounds having physical and chemical
properties resembling those of benzene. { ¦ar ə¦mad ik }

armchair nanotube

armchair nanotube [PHYS CHEM] A carbon nanotube formed from a graphite sheet that
is rolled up so that the edge is in the shape of armchairs. { a¨rm cha¯ r nan o¯ tu¨b }

aristolochic acid

aristolochic acid [ORG CHEM] C17H11NO7 Crystals in the form of shiny brown leaflets
that decompose at 281–286 C; soluble in alcohol, chloroform, acetone, ether, acetic
acid, and aniline; used as an aromatic bitter. Also known as aristolochine. { ə¦ris
tə¦la¨ k ik as əd }


argon [CHEM] A chemical element, symbol Ar, atomic number 18, atomic weight
39.998. { ar ga¨n }


argentometry [ANALY CHEM] A volumetric analysis that employs precipitation of insoluble
silver salts; the salts may be chromates or chlorides. { a¨ r jən ta¨m ə tre¯ }


argentocyanides [INORG CHEM] Complexes formed, for example, in the cyanidation of
silver ores and in electroplating, when silver cyanide reacts with solutions of soluble
metal cyanides. Also known as dicyanoargentates. { a¨ r jen to¯ sı¯ ə nı¯dz }


arecoline [ORG CHEM] C8H13O2N An alkaloid from the betel nut; an oily, colorless liquid
with a boiling point of 209 C; soluble in water, ethanol, and ether; combustible;
used as a medicine. { ə rek ə le¯n }

arc spectrum

arc spectrum [SPECT] The spectrum of a neutral atom, as opposed to that of a molecule or an ion; it is usually produced by vaporizing the substance in an electric arc;
designated by the roman numeral I following the symbol for the element, for example,
HeI. { a¨ rk spek trəm }


arbutin [ORG CHEM] C12H16O7 A bitter glycoside from the bearberry and certain other
plants; sometimes used as a urinary antiseptic. { a¨ r byu¨ t ən }


aralkyl [ORG CHEM] A radical in which an aryl group is substituted for an alkyl H atom.
Derived from arylated alkyl. { a ral kil }


arabitol [ORG CHEM] CH2OH(CHOH)3CH2OH An alcohol that is derived from arabinose;
a sweet, colorless crystalline material present in D and L forms; soluble in water;
melts at 103 C. Also known as arabite. { ə rab ə to˙ l }


aquation [CHEM] Formation of a complex that contains water by replacement of other
coordinated groups in the complex. { ə kwa¯ shən }

aqua regia

aqua regia [INORG CHEM] A fuming, highly corrosive, volatile liquid with a suffocating
odor made by mixing 1 part concentrated nitric acid and 3 parts concentrated
hydrochloric acid; reacts with all metals, including silver and gold. { ¦a¨ k wə re¯ jə }


aquametry [ANALY CHEM] Analytical processes to measure the water present in materials;
methods include Karl Fischer titration, reactions with acid chlorides and anhydrides,
oven drying, distillation, and chromatography. { ə kwa¨m ə tre¯ }


apodization [SPECT] A mathematical transformation carried out on data received from
an interferometer to alter the instrument’s response function before the Fourier
transformation is calculated to obtain the spectrum. { a pə də za¯ shən }


apoatropine [ORG CHEM] C17H21NO2 An alkaloid melting at 61 C with decomposition
of the compound; highly toxic; obtained by dehydrating atropine. { ap o¯ a trə pe¯n }


apo- [CHEM] A prefix that denotes formation from or relationship to another chemical
compound. { ap o¯ or ap ə }

anti-Stokes lines

anti-Stokes lines [SPECT] Lines of radiated frequencies which are higher than the
frequency of the exciting incident light. { an te¯ sto¯ ks lı¯nz }


antioxidant [PHYS CHEM] A substance that, when present at a lower concentration than
that of the oxidizable substrate, significantly inhibits or delays oxidative processes,
while being itself oxidized. In primary antioxidants, antioxidative activity is implemented
by the donation of an electron or hydrogen atom to a radical derivative,
and in secondary antioxidants by the removal of an oxidative catalyst and the
consequent prevention of the initiation of oxidation. Antioxidants are used in polymers
to prevent degradation, and in foods, beverages, and cosmetic products to
inhibit deterioration and spoilage. { an te¯ a¨ k sə dənt }

antimony trisulfide

antimony trisulfide [INORG CHEM] Sb2S3 Black and orange-red rhombic crystals; soluble
in concentrated hydrochloric acid and sulfide solutions, insoluble in water; melting
point 546 C; used as a pigment, and in matches and pyrotechnics. { an tə mo¯
ne¯ trı¯ səl fı¯d }

antimony trichloride

antimony trichloride [INORG CHEM] SbCl3 Hygroscopic, colorless, crystalline mass;
fumes slightly in air, is soluble in alcohol and acetone, and forms antimony oxychloride
in water; used as a mordant, as a chlorinating agent, and in fireproofing textiles.
{ an tə mo¯ ne¯ trı¯ klo˙ r ı¯d }

antimony pentasulfide

antimony pentasulfide [INORG CHEM] Sb2S5 An orange-yellow powder; soluble in alkali,
soluble in concentrated hydrochloric acid, with hydrogen sulfide as a by-product,
and insoluble in water; used as a red pigment. Also known as antimony persulfide;
antimony red; golden antimony sulfide. { an tə mo¯ ne¯ pent ə səl fı¯d }

antimony pentafluoride

antimony pentafluoride [INORG CHEM] SbF5 A corrosive, hygroscopic, moderately viscous
fluid; reacts violently with water; forms a clear solution with glacial acetic acid;
used in the fluorination of organic compounds. { an tə mo¯ ne¯ pent ə flu˙ r ı¯d }

antimony pentachloride

antimony pentachloride [INORG CHEM] SbCl5 A reddish-yellow, oily liquid; hygroscopic,
it solidifies after moisture is absorbed and decomposes in excess water; soluble in
hydrochloric acid and chloroform; used in analytical testing for cesium and alkaloids,
for dyeing, and as an intermediary in synthesis. Also known as antimony perchloride.
{ an tə mo¯ ne¯ pent ə klo˙ r ı¯d }


antimonide [INORG CHEM] A binary compound of antimony with a more positive compound,
for example, H5Sb. Also known as stibide. { an tə mə nı¯d }


antimonate [CHEM] The radical [Sb(OH)6] in salts derived from antimony pentoxide,
Sb4O10, and bases. { an tə mə na¯t }


antifreeze [CHEM] A substance added to a liquid to lower its freezing point; the principal
automotive antifreeze component is ethylene glycol. { an te¯ fre¯z }

antifoaming agent

antifoaming agent [ORG CHEM] A substance, such as silicones, organic phosphates,
and alcohols, that inhibits the formation of bubbles in a liquid during its agitation
by reducing its surface tension. { ¦an te¯ ¦fo¯m iŋ a¯ jənt }


anticatalyst [CHEM] A material that slows down the action of a catalyst; an example
is lead, which inhibits the action of platinum. { ¦an te¯ kad əl ist }


antiaromatic [CHEM] A cyclic compound with delocalized electrons that does not obey
Hu¨ ckel’s rule, and is much less stable than similar nonaromatic compounds. { an
te¯ ar ə mad ik }


anti [ORG CHEM] In stereochemistry, on the opposite side of a reference plane; for
example, the stereochemical outcome of an addition reaction where the new bonds
are on the opposite side of the original pi bond is called anti addition. { an te¯ }


anthrone [ORG CHEM] C14H10O Colorless needles with a melting point of 156 C; soluble
in alcohol, benzene, and hot sodium hydroxide; used as a reagent for carbohydrates.
{ an thro¯n }


anthraquinone [ORG CHEM] C6H4(CO)2C6H4 Yellow crystalline diketone that is insoluble
in water; used in the manufacture of dyes. { an thrə kwi no¯n }


anthrapurpurin [ORG CHEM] C6H3OH(CO)2C6H2(OH)2 Orange-yellow, crystalline needles
with a melting point of 369 C; soluble in alcohol and alkalies; used in dyeing.
{ an thrə pər pə rin }

anthranilic acid

anthranilic acid [ORG CHEM] o-NH2C6H4COOH A white or pale yellow, crystalline acid
melting at 146 C; used as an intermediate in the manufacture of dyes, pharmaceuticals,
and perfumes. { ¦an thrə¦lin ik as əd }


anthracene [ORG CHEM] C14H10 A crystalline tricyclic aromatic hydrocarbon, colorless
when pure, melting at 218 C and boiling at 342 C; obtained in the distillation of
coal tar; used as an important source of dyestuffs, and in coating applications.
{ an thrə se¯n }


antarafacial [ORG CHEM] The stereochemistry when, simultaneously, two sigma bonds
are formed or broken on the opposite faces of the component pi systems, such as
in a cycloaddition reaction. { an tə rə fa¯ shəl }


anomer [ORG CHEM] One of a pair of isomers of cyclic carbohydrates; resulting from
creation of a new point of symmetry when a rearrangement of the atoms occurs at
the aldehyde or ketone position. { an ə mər }

anomalous Zeeman effect

anomalous Zeeman effect [SPECT] A type of splitting of spectral lines of a light source
in a magnetic field which occurs for any line arising from a combination of terms
of multiplicity greater than one; due to a nonclassical magnetic behavior of the
electron spin. { ə na¨m ə ləs za¯ ma¨n i fekt }


anolyte [CHEM] The part of the electrolyte at or near the anode that is changed in
composition by the reactions at the anode. { an ə lı¯t }

anode effect

anode effect [PHYS CHEM] A condition produced by polarization of the anode in the
electrolysis of fused salts and characterized by a sudden increase in voltage and a
corresponding decrease in amperage. { a no¯d i fekt }


annulene [ORG CHEM] One of a group of monocyclic conjugated hydrocarbons which
have the general formula [ CH CH ]n. { an yə le¯n }


anisole [ORG CHEM] C6H5OCH3 A colorless liquid that is soluble in ether and alcohol,
insoluble in water; boiling point is 155 C; vapors are highly toxic; used as a solvent
and in perfumery. { an ə so¯ l }

anisic alcohol

anisic alcohol [ORG CHEM] C8H10O2 A colorless liquid that boils in the range 255–265 C;
it is obtained by reduction of anisic aldehyde; used in perfumery, and as an intermediate
in the manufacture of pharmaceuticals. { ə nis ik al kə ho˙ l }

anisic acid

anisic acid [ORG CHEM] CH3OC6H4COOH White crystals or powder with a melting point
of 184 C; soluble in alcohol and ether; used in medicine and as an insect repellent
and ovicide. { ə nis ik as əd }


anisaldehyde [ORG CHEM] C6H4(OCH3)CHO A compound with melting point 2.5 C,
boiling point 249.5 C; insoluble in water, soluble in alcohol and ether; used in
perfumery and flavoring, and as an intermediate in production of antihistamines.
{ ¦a nəs al də hı¯d }


anionotropy [CHEM] The breaking off of an ion such as hydroxyl or bromide from a
molecule so that a positive ion remains in a state of dynamic equilibrium. { ¦a nı¯
ə na¨ trə pe¯ }

anionic polymerization

anionic polymerization [ORG CHEM] A type of polymerization in which Lewis bases,
such as alkali metals and metallic alkyls, act as catalysts. { ¦a nı¯¦a¨n ik pə lim ə
rə za¯ shən }

Determination of Barium: Direct Titration using Methyl Thymol Blue as indicator

Determination of Barium: Direct Titration using Methyl Thymol Blue as indicator

can you determine the barium ion by EDTA titration
determine the concentration of barium ions in a solution by direct titration with methyl thymol blue 
you can determine the barium ion in sulfate by determination of barium sulfate,determination of barium sulphate, determination of barium in water and determination of barium in drinking water by this method
determination of barium


Complexometric titration of Barium(II) ions directly with EDTA can only be
effected in alkaline solution since the complex is broken down in acidic media. Methyl
Thymol Blue is used as indicator which is grey when it is free (H4ln) and blue when
complexed with Barium.


1- Barium ions solution (analyte)
2- 1M sodium hydroxide solution (pH 12)
3- Methyl Thymol Blue indicator 
4- 0.01 M EDTA solution


1- Pipette 25.0 mL of Barium ions solution into a 250.0 mL and dilute to about
100mL with de-ionised water. Adjust the pH of the solution to 12 by the
addition of 3-6 mL of 1M sodium hydroxide solution.
2- Add 50 mg of methyl thymol blue indicator.
3- Titrate with 0.01 M EDTA until the color changes from blue to grey. Record
the used volume (as VEDTA).
4- Repeat the titration twice

Atomic weight of Barium = 137.34 g/mol