The pH Of Solutions The concept of pH is very convenient for expressing Hydrogen ion concentration.It was introduced by SORENSEN in 1909.Hydrogen ion concentration [H + ] are typically quite small numbers.Therefore,it can be expressed in terms of pH. pH is defined as the negative logarithm(log) of the base 10 of the H + concentration. Mathematically,it may be expressed as pH = -log[ H + ],where[ H + ] is the concentration of hydrogen ion in moles per litre. To calculate Hydrogen ion concentration we go through following step: Pure water ionises as follows- H 2 O  ⇌ H + +  OH - We can write the equilibrium expression as K = [H + ][OH - ] / [H 2 O] Since,water is so little dissociated,the concentration of on-dissociated molecules[H 2 O], is presumed to be constant.We can write K [H 2 O] = [H][OH - ] Kw = [ H + ][OH - ] where Kw is called product of ionic water and is value is 1 x 10 -14 at 25℃,i.e Kw = [ H + ][OH - ] log Kw = log[ H + ] + log[OH - ] -log Kw = -log[ H + ] - log[OH - ]

This Blog shows discussion of several topics important to the preparation,preservation and storage of pharmaceutical products.The major topics include ACIDS and BASES - frequently employed in the conversion of drugs to chemical forms convenient to their product formulation;BUFFERS - used to maintain the pH of various formulations within Prescribed Limits .