Hydrogen indicator

HYDROGEN INDICATOR, pH (EN: pH-value; DE: pH-Wert; FR: pH valeur; ES: valor del pH; RU: водородный показатель), characterizes the concentration (more accurately, the activity) of the ions of hydrogen within the solutions; this indicator is numerically equal to the negative decimal logarithm of the concentration of the ions of hydrogen (in terms of the grams of ions per 1 litre): pH = -lg[H+] grams of ions per litre, where [H+] is the concentration of the ions of hydrogen. The concept of the pH has been introduced during the start of the 20th century for the convenience of the calculations, which are associated with the concentration of the ions of hydrogen. The pH of the aqueous solutions is from 0 to 14. The solutions, which, at the temperature of 22 degrees Celsius, are having the pH > 7, are considered as alkaline, the pH = 7, as neutral, and the pH < 7, as acidic.

They usually determine the hydrogen indicator, using the acidic-alkaline indicators, which are changing their colouration with the changing of the pH, or more accurately, using the potentiometric method.

The hydrogen indicator influences the direction and speed of the proceeding of many chemical reactions and biochemical processes. The determination of the pH is required within the processes of the flotation, hydrometallurgy, purification of the waste waters, and so on.