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A gradient of red cabbage extract pH indicator from acidic solution on the left to basic on the right. Red cabbage contains an anthocyanin-based dye that can be used as a pH indicator. It is red, pink, or magenta in acids (pH < 7), purple in neutral solutions (pH ≈7), and ranges from blue to green to yellow in alkaline solutions (pH > 7). [7]
Extracting anthocyanins from household plants, especially red cabbage, to form a crude pH indicator is a popular introductory chemistry demonstration. Litmus, used by alchemists in the Middle Ages and still readily available, is a naturally occurring pH indicator made from a mixture of lichen species, particularly Roccella tinctoria.
Red cabbage extract at low pH (left) to high pH (right) Anthocyanins generally are degraded at higher pH. However, some anthocyanins, such as petanin (petunidin 3-[6- O -(4- O -( E )- p -coumaroyl- O -α- l -rhamnopyranosyl)-β- d -glucopyranoside]-5- O -β- d -glucopyranoside), are resistant to degradation at pH 8 and may be used effectively ...
The buffering capacity of the water probably overwhelmed the small amount of acid in the cabbage drippings, bringing the pH back to ~7 and turning the color blue. It's not that the tap water was very basic, it's just that it was less acidic than the juice. -- 174.21.247.23 ( talk ) 04:10, 17 February 2010 (UTC) [ reply ]
Phenol red exists as a red crystal that is stable in air. Its solubility is 0.77 grams per liter (g/L) in water and 2.9 g/L in ethanol. [1] It is a weak acid with pK a = 8.00 at 20 °C (68 °F). A solution of phenol red is used as a pH indicator, often in cell culture.
A roll of universal indicator paper Colors of universal indicator. A universal indicator is a pH indicator made of a solution of several compounds that exhibit various smooth colour changes over a wide range pH values to indicate the acidity or alkalinity of solutions. A universal indicator can be in paper form or present in a form of a ...
Phenolphthalein, commonly used as a pH indicator, turns pink in the presence of a base such as ammonia fumes or sodium carbonate. Vinegar, is revealed by red cabbage water [12] Vinegar contains acetic acid that affects the pH indicator in red cabbage water. Vinegar may also be developed by heat. Ammonia, developed by red cabbage water.
The neutral red is also used to stain cell cultures for plate titration of viruses. Neutral red is added to some growth media for bacterial and cell cultures. It usually is available as a chloride salt. Neutral red acts as a pH indicator, changing from red to yellow between pH 6.8 and 8.0.