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A small amount of phenol red added to this growth medium will have a pink-red color under normal conditions. Typically, 15 mg/L are used for cell culture. In the event of problems, waste products produced by dying cells or overgrowth of contaminants will cause a change in pH, leading to a change in indicator color.
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 the solution and on the temperature at which it is used. The figure on the right shows indicators with their operation range and color changes.
The doubly deprotonated (In 2-) phenolate form (the anion form of phenol) gives the familiar pink color. In strongly basic solutions, phenolphthalein is converted to its In(OH) 3− form, and its pink color undergoes a rather slow fading reaction [6] and becomes completely colorless when pH is greater than 13.
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 ...
This category contains articles about pH indicators: chemical compounds which change colour or fluorescence in response to changes in pH Wikimedia Commons has media related to PH indicators . Subcategories
Chlorophenol red is an indicator dye that changes color from yellow to violet in the pH range 5.4 to 6.8. [2] The pH of a substance is determined by taking the negative logarithm of the Hydronium ion concentration and the indictor changes color due to the dissociation of H + ions. [3] The lambda max is at 572 nm. [4]
These byproducts are usually acids, which will change the color of the red pH-sensitive dye (phenol red) to a yellow color. Position of the color change distinguishes the acid production associated with glucose fermentation from the acidic byproducts of lactose or sucrose fermentation. . If this occurs, the newly formed hydrogen sulfide (H
Staphylococcus aureus produces yellow colonies with yellow zones, whereas other coagulase-negative staphylococci produce small pink or red colonies with no colour change to the medium. [4] If an organism can ferment mannitol, an acidic byproduct is formed that causes the phenol red in the agar to turn yellow. [ 1 ]
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