A pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH (acidity or alkalinity) of the solution can be determined easily. Hence a pH indicator is a chemical detector for hydronium ions (H₃O⁺) (or Hydrogen ions (H⁺) in the Arrhenius model). Normally, the indicator causes the colour of the solution to change depending on the pH. pH values above 7.0 are basic, and pH values below 7.0 are acidic. Solutions with a pH value of 7.0 are neutral. Most pH values range from 1 to 14, but superacids may have a negative pH value. Similarly, superbases may have pH values greater than 14. Along with smart materials that have the ability to change colour in response with heat and light there are a similar set of materials which are responsive to pH. The pH of a substance is how acidic or basic the substance is. ... A chemical compound is a chemical substance of two or more different chemically bonded chemical elements, with a fixed ratio determining the composition. ... Making a saline water solution by dissolving table salt (NaCl) in water This article is about chemical solutions. ... For other uses, see PH (disambiguation). ... For other uses, see acid (disambiguation). ... Acids and bases: Acid-base reaction pH Self-ionization of water Buffer solutions Systematic naming Acid-base extraction Acidity function Proton affinity Acids: Strong acids Weak acids Superacids Lewis acids Mineral acids Organic acids Bases: Strong bases Weak bases Superbases Lewis bases Organic bases edit In chemistry, a base is... A chemical substance is any material substance used in or obtained by a process in chemistry: A chemical compound is a substance consisting of two or more chemical elements that are chemically combined in fixed proportions. ... In chemistry, hydronium is the common name for the cation H3O+ derived from protonation of water. ... Acids and bases: Acid-base reaction theories pH Self-ionization of water Buffer solutions Systematic naming Electrochemistry Acid-base extraction Acids: Strong acids Weak acids Mineral acids Organic acids Bases: Strong bases Weak bases Organic bases edit An acid-base reaction is a chemical reaction between an acid and a... Color is an important part of the visual arts. ... A superacid is an acid with an acidity greater than that of 100% sulfuric acid. ... In chemistry, a superbase is an extremely strong base. ...

Theory

pH indicators themselves are frequently weak acids or bases. When introduced into a solution, they may bind to H⁺ (Hydrogen ion) or OH^- (hydroxide) ions. The different electron configurations of the bound indicator causes the indicator's colour to change. General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: OH− It has a charge of −1. ... Electron atomic and molecular orbitals In atomic physics and quantum chemistry, the electron configuration is the arrangement of electrons in an atom, molecule, or other physical structure (, a crystal). ...

Application

pH indicators are frequently employed in titrations in analytic chemistry and biology experiments to determine the extent of a chemical reaction. Because of the subjective determination of color, pH indicators are susceptible to imprecise readings. For applications requiring precise measurement of pH, a pH meter is frequently used. Titration setup: the titrant drops from the burette into the analyte solution in the flask. ... For other uses, see Chemistry (disambiguation). ... Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology (from Greek: βίος, bio, life; and λόγος, logos, knowledge), also referred to as the biological sciences, is the study of living organisms utilizing the scientific method. ... For other uses, see Chemical reaction (disambiguation). ... This article is in need of attention. ... A pH meter is an electronic instrument used to measure the pH (acidity or basicity) of a liquid (though special probes are sometimes used to measure the pH of semi-solid substances, such as cheese). ...

Tabulated below are several common laboratory pH indicators. Indicators usually exhibit intermediate colors at pH values inside the listed transition range. For example, phenol red exhibits an orange color between pH 6.8 and pH 8.4. The transition range may shift slightly depending on the concentration of the indicator in solution and on the temperature at which it is used.

Methyl Violet 10B Gentian violet (crystal violet, Methyl Violet 10B, hexamethyl pararosaniline chloride) is an antifungal agent. ... Structure of Methyl Violet 2B Methyl violet is the name given to a group of similar chemicals used as pH indicators and dyes. ... Malachite green, also called aniline green, basic green 4, diamond green B, or victoria green B, IUPAC name:4-[(4-dimethylaminophenyl)-phenyl-methyl]-N,N-dimethyl-aniline) is a toxic chemical primarily used as a dye. ... Thymol blue is a brownish-green crystal powder that is used as an pH indicator. ... Methyl yellow is a chemical compound which may be used as a pH indicator. ... Bromophenol Blue Bromophenol blue, Tetrabromophenolsulfonphthalein, is an acid-base indicator whose useful range as an indicator lies between pH 3. ... Chemical structure of congo red Congo red is the sodium salt of benzidinedflandersiazo-bis-1-naphtylamine-4-sulfonic acid (formula: C32H22N6Na2O6S2; molecular weight: 696. ... Methyl Orange is a pH indicator frequently used in titrations. ... Bromocresol green (3,3,5,5-tetrabromo-m-cresolsulfonphthalein) is a dye of the triphenylmethane family (triarylmethane dyes), which is used as a pH indicator and as a tracking dye for DNA agarose gel electrophoresis. ... The chemical makeup of Methyl Red Methyl Red, also called C.I. Acid Red 2, is an indicator dye that turns red in acidic solutions. ... Litmus is a water-soluble mixture of different dyes extracted from lichens, specially Roccella tinctoria. ... Bromocresol purple,or 5,5-dibromo-o-cresolsulfophthalein, is a pH indicator with the chemical formula C21H16Br2O5S. // Chemical properties The compound, with a molecular weight of 540. ... Bromothymol Blue (also known as dibromothymolsulfonephthalein, Bromthymol Blue, and BTB) is a chemical indicator for weak acids and bases. ... Phenol red (also known as phenolsulfonphthalein or PSP) is a pH indicator that is frequently used in cell biology laboratories. ... Neutral Red (or toluylene red, Basic Red 5, or C.I. 50040) is an eurhodin dye used for staining in histology. ... chemical structure of 1-Naphtholphthalein α-Naptholphthalein (C28H18O4) is a pH indicator. ... Cresol Red (full name: o-Cresolsulfonephthalein) is a triarylmethane dye frequently used for monitoring the pH in aquaria. ... Phenolphthalein is a sensitive chemical with the formula C20H14O4 (often written as HIn in shorthand notation). ... Thymolphthalein is an acid-base (pH) indicator. ... Alizarine Yellow R (Chrome Orange, Mordant Orange 1) is a yellow colored azo dye made by the diazo coupling reaction. ...

Commercial preparations

pH measurement with indicator paper.

Universal indicator and Hydrion papers are blends of different indicators that exhibits several smooth color changes over a wide range of pH values. Image File history File linksMetadata Size of this preview: 349 × 599 pixel Image in higher resolution (1172 × 2012 pixel, file size: 772 KB, MIME type: image/jpeg) pH measurement with an indicator paper. ... Image File history File linksMetadata Size of this preview: 349 × 599 pixel Image in higher resolution (1172 × 2012 pixel, file size: 772 KB, MIME type: image/jpeg) pH measurement with an indicator paper. ... This article or section cites very few or no references or sources. ... Hydrion is a trademarked name for a popular line of compound pH indicators, marketed by Micro Essentials Laboratory, exhibiting a series of color changes (typically producing a recognizably different color for each pH unit) over a range of pH values. ...

Naturally occurring pH indicators

Hydrangeas can change colour with soil acidity

Many plants or plant parts contain chemicals from the naturally-colored anthocyanin family of compounds. They are red in acidic solutions and blue in basic. Extracting anthocyanins from red cabbage leaves to form a crude acid-base indicator is a popular introductory chemistry demonstration. Image File history File links Download high resolution version (1600x1067, 321 KB) Light Mauve Hydrangea File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Hydrangea ... Image File history File links Download high resolution version (1600x1067, 321 KB) Light Mauve Hydrangea File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Hydrangea ... Species See text Hydrangea (common names also Hydrangea, in English pronounced IPA , and Hortensia) is a genus of about 70-75 species of flowering plants native to southern and eastern Asia (from Japan to China, the Himalaya and Indonesia) and North and South America. ... Plants with abnormally high anthocyanin quantities are popular as ornamental plants - here, a selected purple-leaf cultivar of European Beech Anthocyanins (from Greek: (anthos) = flower + (kyanos) = blue) are water-soluble vacuolar flavonoid pigments that appear red to blue, according to pH. They are synthesized exclusively by organisms of the plant... Cultivar Group Brassica oleracea Capitata Group The Red Cabbage (Brassica oleracea var. ...

Anthocyanins can be extracted from a multitude of colored plants or plant parts, including from leaves (red cabbage); flowers (geranium, poppy, or rose petals); berries (blueberries, blackcurrant); and stems (rhubarb). An exhaustive list would be beyond the scope of this article. Percentages are relative to US recommendations for adults. ... Not to be confused with germanium. ... This article is about the plant. ... For other uses, see Rose (disambiguation). ... For other uses, see Blueberry (disambiguation). ... It is a myth that people either go crazy for the flavor or they totally dislike it. ... Species About 60, including: R. nobile R. palmatum For other uses see Rhubarb (disambiguation) Rhubarb is a perennial plant that grows from thick short rhizomes, comprising the genus Rheum. ...

References

Wikimedia Commons has media related to:

pH indicator

• Long indicator list
• (French) Complete indicator listPDF

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