Permanganometry is one of the techniques used in

chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wi ...

quantitative analysis. It is a

redox titration A redox titration is a type of titration based on a redox reaction between the analyte and titrant. It may involve the use of a redox indicator and/or a potentiometer. A common example of a redox titration is treating a solution of iodine with a ...

that involves the use of

permanganate A permanganate () is a chemical compound containing the manganate(VII) ion, , the conjugate base of permanganic acid. Because the manganese atom is in the +7 oxidation state, the permanganate(VII) ion is a strong oxidizing agent. The ion is a tra ...

s to measure the amount of

analyte An analyte, component (in clinical chemistry), or chemical species is a substance or chemical constituent that is of interest in an analytical procedure. The purest substances are referred to as analytes, such as 24 karat gold, NaCl, water, etc. ...

present in unknown chemical samples. It involves two steps, namely the

titration Titration (also known as titrimetry and volumetric analysis) is a common laboratory method of quantitative chemical analysis to determine the concentration of an identified analyte (a substance to be analyzed). A reagent, termed the ''titrant'' ...

of the analyte with

potassium permanganate Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and , an intensely pink to purple solution. Potassium permanganate is widely used in the c ...

solution and then the standardization of potassium permanganate solution with standard

sodium oxalate Sodium oxalate, or disodium oxalate, is the sodium salt of oxalic acid with the formula Na2C2O4. It is a white, crystalline, odorless solid, that decomposes above 290 °C. Disodium oxalate can act as a reducing agent, and it may be used as a pr ...

solution. The titration involves volumetric manipulations to prepare the analyte solutions. Permanganometry allows the detection and estimation of the quantitative presence of various chemical species, such as

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

(II),

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

(II),

oxalate Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl o ...

nitrite The nitrite polyatomic ion, ion has the chemical formula . Nitrite (mostly sodium nitrite) is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name ...

, and

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

Reaction

Depending on the conditions in which the titration is performed, the manganese is reduced from an oxidation of +7 to +2, +4, or +6. In most cases, permanganometry is performed in a very acidic solution in which the following

electrochemical Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outco ...

reaction occurs: : + 8 H⁺ + 5 e⁻ → Mn²⁺ + 4 H₂O; ''E''° = +1.51 V which shows that KMnO₄ (in an acidic medium) is a very strong oxidizing agent, able to oxidize Fe²⁺ (''E''°_{Fe³⁺/Fe²⁺} = +0.77 V), Sn²⁺ (''E''°_{Sn⁴⁺/Sn²⁺} = +0.2 V), and even Cl⁻ (''E''°_Cl₂/Cl⁻ = +1.36 V). In weak acidic medium can not accept 5 electrons to form Mn²⁺. Instead, it accepts only 3 electrons and forms solid MnO₂ by the following reaction: : + 4 H⁺ + 3 e⁻ → MnO₂ + 2 H₂O; ''E''° = +1.69 V In a strongly

basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...

solution, with the

concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', an ...

c_(NaOH) >1 mol dm⁻³, only one electron is accepted to produce

manganate In inorganic nomenclature, a manganate is any negatively charged molecular entity with manganese as the central atom.. However, the name is usually used to refer to the tetraoxidomanganate(2−) anion, MnO, also known as manganate(VI) because it c ...

: : + e⁻ → ; ''E''° = +0.56 VLouis Rosenfeld. ''Four Centuries of Clinical Chemistry''. CRC Press, 1999, p. 72-75.

References

{{reflist Analytical chemistry Titration