Safety Emporium for all your lab and safety needs

Peroxide

Glossary Index

Phlegm

MSDS Topics	Free Sites	FAQ's	Regulations	Glossary	Software	Suppliers
	Books	Forum	Poll	Fun stuff	Quiz	Store
Understand your MSDS with the MS-Demystifier				Search ALL our MSDS info

pH

Definition

The pH of a solution is the negative logarithm of the hydrogen ion (H+) concentration (in moles per liter = molarity). Chemists write "hydrogen ion concentration" as [H+]. pH tells you whether a solution is acidic, basic or neutral. The corresponding ranges are: Acidic - the pH is between zero and 7.0 Neutral - the pH is 7.0 Basic (also called alkaline) - the pH is between 7.0 and 14. For strong acids or bases, these values may actually be higher than 14 or lower than 0, but the 0-14 range is most commonly encountered.

These D.O.T.-required labels, signs and placards are available at Safety Emporium.

Additional Info

The pH scale is logarithmic. That means each change of one in pH value is 10 times more acidic. Therefore, a substance with a pH of 2 is 1000 times more acidic than one with a pH of 5!

The pH values of some common substances are given in the table below.

Substance	Typical pH	[H+], M
Stomach acid (gastric juices)	1.4	0.0398
Lemon juice	2.4	0.00398
Vinegar	3.0	1 x 10-3
Tomatoes	4.2	6.31 x 10-5
Water exposed to air	5.5	3.16 x 10-6
Pure water	7.0	1 x 10-7
Blood or tears	7.4	3.98 x 10-8
Baking soda	8.4	3.98 x 10-9
Household ammonia	11.5	3.16 x 10-12
Household bleach	12.5	6.31 x 10-13

MSDS Relevance

Signs, labels, emergency eyewashes and safety showers from Safety Emporium can increase your workplace safety.

It is important to know the pH of substances because they may be corrosive or react with incompatible materials. For example acids and bases should not be stored or used near each other as their accidental combination could generate a huge amount of heat and energy, possibly resulting in an explosion. pH is also important to know in case you spill the material on your skin or eyes. Whenever a substance enters the eye, flush with water for 15 minutes and get prompt medical attention. If a basic substance enters the eye this is particularly important as basic materials tend to cause worse eye damage and are harder to flush out of the eye tissues than acidic materials.

Further Reading

• University of Akron has slides concerning acid-base chemistry and pH.
• Acids, Bases, and Salts at ScienceByJones.com.
• Acids Bases and Salts at ChemistryCoach.com.
• Acids and Bases at ChemTutor.com.
• pH facts.

See also: acid, base.

Disclaimer: The information contained herein is believed to be true and accurate, however ILPI makes no guarantees concerning the veracity of any statement. Use of any information on this page is at the reader's own risk. ILPI strongly encourages the reader to consult the appropriate local, state and federal agencies concerning the matters discussed herein.