Preventing Chemical Accidents: Understanding MSDS’s & Assessing Chemical Hazards
Material Safety Data Sheet, www.afscme.org/health/faq-msds.htm
pH: A Basic Chemical Term
The pH of a chemical tells you if the chemical is an acid, a base (also called alkali or caustic), or neutral. The pH scale goes from 0 to 14, with 7 being neutral (water is neutral with a pH of 7).
pH less than 7 = acid
pH more than 7 = base
Strong Acid Neutral Strong Base
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
The lower the pH (below 7), the stronger the acid. The higher the pH (above 7), the stronger the base. Many organic hydrocarbons (e.g., gasoline, benzene, kerosene, etc.) have almost neutral pHs (close to 7).
Here are some things to remember about pH:
• Chemicals with a pH much lower or much higher than 7 will cause irritation and burns to the part of the body coming into contact with the material.
• Basic chemicals (those with a pH above 7) are much more dangerous to the eyes than are acids. Acids “sit” on the surface of the eyes, if splashed, and can therefore be washed off (if done quickly), often without resulting in permanent damage.
• Base substances rapidly penetrate the eye tissue, often causing quick and lasting damage.
• Store like with like. Chemicals with lower or higher pH should only be stored with chemicals of like pH and never with their opposite or