pH is the measure of the acidity of a solution. H stands for Hydrogen and p for power. pH defines the activity of dissolved hydrogen ions in a solution. Acidic liquids typically have positively charged hydrogen molecules and alkaline liquids have negatively charged hydrogen molecules. These positively or negatively charged hydrogen molecules cause strong reactions with other materials. The caustic strength of a solution is nothing else than their potential to react with other materials. The negatively charged hydrogen molecules are drawn to the positively charges molecules and the positively charged molecules are drawn to negatively charged molecules. Hydrogen molecules that have the potential to move are called ions. An ion, from the Greek meaning “moving molecule”, is a negatively or positively charged hydrogen molecule. The pH value measures the concentration of positively charged hydrogen ions in an acidic or alkaline solution. The pH scale ranges from “0” to “14”, the strongest alkaline value is “14” and the strongest acid value is “0”. The middle value of “7” indicates a neutral solution that has an equal number of positively and negatively charged ions, therefore the solution is neither acidic nor alkaline.
The numerical values of the pH-scale indicate the 10th power, for example, the strength of caustic acid is 10 times stronger with every step on the pH scale (see graphic display).