👉 An indicating fluid, also known as an indicator or pH indicator, is a chemical substance that changes color in response to the acidity or alkalinity of a solution. These indicators are crucial in various scientific and medical applications, such as pH measurement, monitoring blood acidity (pH levels), and detecting chemical reactions. Common examples include phenolphthalein, which turns pink in basic solutions (pH > 8.2), and methyl orange, which changes from red in acidic solutions (pH < 3.1) to yellow in basic ones (pH > 4.4). The color change is due to the indicator's molecular structure, which alters its ability to absorb light at different wavelengths depending on the solution's pH. This property makes indicating fluids invaluable in experiments and diagnostic tests where precise pH measurements are necessary.
