PH indicators

right|thumb|Litmus powder right|thumb|Chemical structure of 7-hydroxyphenoxazone, the chromophore of litmus components

Phenolphthalein ( ) is a chemical compound with the formula C20H14O4 and is often written as "HIn", "HPh", "phph" or simply "Ph" in shorthand notation. Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions. It belongs to the class of dyes known as phthalein dyes.

right|thumb|Purple cauliflower contains anthocyanins. thumb|right|Anthocyanins are glycosides of [[anthocyanidins, the basic chemical structure of which is shown here.]]

pH indicator

halochromic chemical compound added in small amounts to a solution so the pH of the solution can be determined visually

chemical compound

triarylmethane dye used as a histological stain and in Gram's method of classifying bacteria

chemical compound

chemical compound

chemical compound

chemical compound

chemical compound

chemical compound

dye

Thymolphthalein is a phthalein dye used as an acid–base (pH) indicator. Its transition range is around pH 9.3–10.5. Below this pH, it is colorless; above, it is blue. The molar extinction coefficient for the blue thymolphthalein dianion is 38,000 M−1 cm−1 at 595 nm.

chemical compound

chemical compound

chemical compound

chemical compound

chemical compound

chemical compound

4-Nitrophenol (also called '''p-nitrophenol or 4-hydroxynitrobenzene''') is a phenolic compound that has a nitro group at the opposite position of the hydroxyl group on the benzene ring.

Cyanidin is a natural organic compound. It is a particular type of anthocyanidin (glycoside version called anthocyanins). It is a pigment found in many red berries including grapes, bilberry, blackberry, blueberry, cherry, chokeberry, cranberry, elderberry, hawthorn, loganberry, açai berry and raspberry. It can also be found in other fruits such as apples and plums, and in red cabbage and red onion. It has a characteristic reddish-purple color, though this can change with pH; solutions of the compound are red at pH 11. In certain fruits, the highest concentrations of cyanidin are found in the

type of pH indicator

chemical compound

thumb|right|200px|Molecule in 3D of the anthocyanidin cyanidin

Wikimedia template

Aurin (C.I. 43800), sometimes named rosolic acid or corallin is an organic compound, forming yellowish or deep-red crystals with greenish metallic luster. It is practically insoluble in water, freely soluble in alcohol. It is soluble in strong acids to form yellow solution, or in aqueous alkalis to form carmine red solutions. Due to this behaviour it can be used as pH indicator with pH transition range 5.0 - 6.8. It is used as an intermediate in manufacturing of dyes.

chemical compound

chemical compound

α-Naphtholphthalein (C28H18O4) is a phthalein dye used as a pH indicator with a visual transition from colorless/reddish to greenish blue at pH 7.3–8.7.

Resazurin (7-Hydroxy-3H-phenoxazin-3-one 10-oxide) is a phenoxazine dye that is weakly fluorescent, nontoxic, cell-permeable, and redox‐sensitive. Resazurin has a blue to purple color above pH 6.5 and an orange color below pH 3.8. It is used in microbiological, cellular, and enzymatic assays because it can be irreversibly reduced to the pink-colored and highly fluorescent resorufin (7-Hydroxy-3H-phenoxazin-3-one). At circum-neutral pH, resorufin can be detected by visual observation of its pink color or by fluorimetry, with an excitation maximum at 530-570 nm and an emission maximum at 58

indicator dye that changes color from yellow to violet in the pH range 4.8 to 6.7

chemical compound

thumb|White cauliflower has anthoxanthin pigments Anthoxanthins () are a type of flavonoid pigments in plants. Anthoxanthins are water-soluble pigments which range in color from a white or colorless to a creamy to a yellow, often on petals of flowers. These pigments are generally whiter in an acid medium and yellowed in an alkaline medium. They are very susceptible to color changes with minerals and metal ions, similar to anthocyanins. Some examples of anthoxanthins include: apigeniun, luteolin, kaempferol, quercetin.

Nitrazine or phenaphthazine is a pH indicator dye often used in medicine. More sensitive than litmus, nitrazine indicates pH in the range of 4.5 to 7.5. Nitrazine is usually used as the disodium salt.

chemical compound

thumb|White wool yarn dyed with "orchella weeds", using traditional Natural dye|plant dye methods. Orcein, also called archil, orchil, lacmus and C.I. Natural Red 28 - CICN 758600, is any dye extracted from several species of lichen, commonly known as "orchella weeds", found in various parts of the world. A major source is the archil lichen, Roccella tinctoria. Orcinol is extracted from such lichens. It is then converted to orcein by ammonia and air. In traditional dye-making methods, urine was used as the ammonia source. If the conversion is carried out in the presence of potassium carbonate,

'''o-Cresolphthalein''' is a phthalein dye used as a pH indicator in titrations. It is insoluble in water but soluble in ethanol. Its solution is colourless below pH 8.2, and purple above 9.8. Its molecular formula is C22H18O4. It is used medically to determine calcium levels in the human body, or to synthesize polyamides or polyimides.

chemical compound

chemical compound

pH indicator

chemical compound