Kolthoff (1926) without particular reference to sea water has defined buffer capacity (alkalinity, in the case of added strong base) of a solution quantitatively as the number of equivalents of added strong base or strong acid required to change the pH of one liter of solution one unit. Buch, in 1930, redefined this concept with reference to sea water as the number of moles of carbonic acid which must be added to one liter of the water in order to change its pH by one unit.