pH:

Many compounds dissolve within water and alter the hydrogen ion concentration. Compounds which generate hydrogen ions straightly while dissolved within water are known as acids, and those which generate hydroxyl ions directly while dissolved in water are known as bases.  For treat these aspects of chemistry more precisely, a quantitative system of expressing acidity or basicity (alkalinity) is required.   This required could be met through using the value of [H⁺], where [H⁺] is expressed within moles/liter, as a measure of acidity. But, in many cases [H+] is in the range of -110 to 10^-14 moles/liter.   Since numbers of this magnitude are inconvenient to work along with, an alternate system for expressing an acidity of dilute solutions has been devised. That system is based on a quantity known as pH.   ph is described as the negative logarithm of the hydrogen concentration it represented as [H⁺] in moles/liter.

pH      =  -log [H⁺]                                                                         (1-1)

[H⁺]     = 10^-pH                                                                             (1-2)

The negative logarithm is specified since the logarithm of any number less than 1 is negative; therefore multiplication through -1 causes the values of pH to be positive over the range in that we are interested. (The word pH was first defined through a Danish chemist and is derived from p for the Danish word potenz (power) and H for hydrogen.)