With an increase in pH (pKa=1.2) the excess proton in the ketone group is lost, resulting in a yellow color. Further increases in pH (pKa=7.7) causes a loss of the hydrogen from the hydroxyl group resulting in a red color. The ratio of these three moieties enables phenol red to be used as a pH indicator dye.22 mar 2018
How do you make phenol red indicator?
Phenol Red Indicator Solution: Dissolve 0.1 g of phenol red in 2.82 ml of 0.1 M sodium hydroxide and 20 ml of ethanol (95 percent). After the solution is effected, add sufficient water to produce 100 ml.
Why is phenol red red?
Phenol red exists as a red crystal that is stable in air. ... A solution of phenol red is used as a pH indicator, often in cell culture. Its color exhibits a gradual transition from yellow (λmax = 443 nm) to red (λmax = 570 nm) over the pH range 6.8 to 8.2. Above pH 8.2, phenol red turns a bright pink (fuchsia) color.
What does phenol red indicate?
Most commonly, phenol red is an indicator dye, used as an acid pH indicator with a transition point of 7.5 (acid side to yellow / alkaline side to red) Biologists use phenol red in cell cultures as a pH indicator. Phenol red has been used in the PSP test for kidney functions.