The pH range that appears pink depends on the specific pH indicator used. Pink isn't associated with a single pH value, but rather a range within which certain indicators change color to pink.
pH Indicators and Pink Coloration
pH indicators are substances that change color depending on the acidity or alkalinity of a solution. Different indicators transition to pink at different pH levels. Here's a breakdown using data from the provided reference:
Phenolphthalein
- pH Range: 8.0 (colorless) - 10 (pink)
- Interpretation: Phenolphthalein is colorless below pH 8.0 and transitions to pink as the pH increases, reaching a distinct pink color around pH 10.
Cresolphthalein (ortho)
- pH Range: 8.2 (colorless) - 9.8 (violet/red)
- Interpretation: Cresolphthalein is colorless until a pH of 8.2, gradually changing to violet/red as pH nears 9.8. This can sometimes be interpreted as a deep pink or light red depending on concentration and observer.
Thymolphthalein
- pH Range: 8.8 (colorless) - 10.5 (blue)
- Interpretation: While not directly pink, Thymolphthalein transitions from colorless to blue within this range, and some intermediate shades might appear as a very pale, almost pinkish-blue depending on the concentration and the observer.
Key Takeaways
- Pink coloration in solutions is generally associated with a slightly alkaline to alkaline pH.
- Phenolphthalein is the most common indicator where pink is a prominent color within its transition range (pH 8.0-10).
- Other indicators, like Cresolphthalein, might exhibit pinkish or reddish hues near their transition points.
Therefore, stating a single pH value for "pink" is inaccurate. The perceived pH of "pink" is highly dependent on the specific indicator being used. Generally, think of a pH between 8 and 10 when you see a solution turn pink when an indicator like phenolphthalein is present.
