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Conversely, if a 10-fold excess of the acid occurs with respect to the base, the ratio is 1:10 and the pH is pK a − 1 or pK b − 1. For optimal accuracy, the color difference between the two species should be as clear as possible, and the narrower the pH range of the color change the better.
The ABC of Acid-Base Chemistry: The Elements of Physiological Blood-Gas Chemistry for Medical Students and Physicians (Sixth ed.). Chicago: The University of Chicago Press. Items portrayed in this file
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. Phenolphthalein is slightly soluble in water and usually is dissolved in alcohols in experiments.
Metanil Yellow (Acid Yellow 36) is a dye of the azo class. In analytical chemistry, it is used as a pH indicator and it has a color change from red to yellow between pH 1.2 and 3.2. [1] Although illegal for food use, Metanil Yellow has been used as an adulterant in turmeric and pigeon pea based food products, particularly in India. [2] [3] [4] [5]
Thymolphthalein is a phthalein dye used as an acid–base 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. [2]
Amphoteric is derived from the Greek word amphoteroi (ἀμφότεροι) meaning "both".Related words in acid-base chemistry are amphichromatic and amphichroic, both describing substances such as acid-base indicators which give one colour on reaction with an acid and another colour on reaction with a base.
Acid–base titrations depend on the neutralization between an acid and a base when mixed in solution. In addition to the sample, an appropriate pH indicator is added to the titration chamber, representing the pH range of the equivalence point. The acid–base indicator indicates the endpoint of the titration by changing color.
Bromophenol is also used as a colour marker to monitor the process of agarose gel electrophoresis and polyacrylamide gel electrophoresis.Since bromophenol blue carries a slight negative charge at moderate pH, it will migrate in the same direction as DNA or protein in a gel; the rate at which it migrates varies according to gel density and buffer composition, but in a typical 1% agarose gel in ...