PH temperature increases. Pure water is neutral, pH 7 at (25 °C), being neither an acid nor a base. Contrary to popular belief, the pH value can be less than 0 or greater than 14 for very strong acids and bases respectively. Measurements of pH are important in agronomy, medicine, chemistry, water treatment, and many other applications. The pH scale is traceable to a set of standard solutions whose pH is established by international agreement. Primary pH standard values are determined using a concentration cell with transference, by measuring the potential difference between a hydrogen electrode and a standard electrode such
PH indicator frequently weak acids or weak bases. The general reaction scheme of a pH indicator can be formulated as: Here, HInd stands for the acid form and Ind for the conjugate base of the indicator. The ratio of these determines the color of the solution and connects the color to the pH value. pH indicators that are weak protolytes, the Henderson–Hasselbalch equation for them can be written as: The equation, derived from the acidity constant, states that when pH equals the p"K" value of the indicator, both species are present in a 1:1 ratio. If pH is above the p"K" value,