pHneutral

pHneutral is a term used to describe a state or condition in which a solution has a neutral pH, typically around 7 at standard room temperature. The pH scale runs from 0 to 14 and expresses how acidic or basic a solution is. pH is defined as the negative logarithm of the hydrogen ion activity, so a pH of 7 corresponds to a balance between hydrogen ions (H+) and hydroxide ions (OH−).

Neutrality is temperature dependent. In pure water at 25°C, the concentrations of H+ and OH− are equal, yielding pH 7. This defines neutrality for that temperature. If the temperature changes, the autoionization of water changes as well, and the neutral pH shifts slightly away from 7. At higher temperatures the neutral pH tends to be below 7, while at lower temperatures it can be above 7. Thus pHneutral is a practical label rather than a universal constant across all conditions.

Measurement of pH is typically done with a calibrated pH meter or with pH indicator strips. Accurate determination requires proper calibration, temperature compensation, and awareness of the sample’s composition. Complex solutions or extreme temperatures can affect readings.

Applications of the concept include cleaning products, cosmetics, and agricultural formulations, where “pHneutral” labeling signals mildness and minimized corrosivity or irritation. However, the exact target pH can vary by product and context, and a label does not always imply a precise pH of 7. Users should consult product specifications for the measured pH.

See also: pH scale, hydrogen ion activity, Kw, pH meter.