By Wes Adams, MS
Both acids and bases can be hazardous to humans and living organisms because of their corrosive properties.
The corrosive effect on skin tissue of an acid is dependant on the concentration of the acid. Human contact with dilute acid may only redden the skin tissue, while contact with a concentrated acid for the same duration may cause blistering. Tissue affected by an acid is said to be "burned" because the damage resembles 1st, 2nd, and 3rd degree burns.
The corrosive effect on skin tissue of a base is also dependant on the concentration of the base. Human contact with dilute base may only redden the skin tissue, while contact with a concentrated base may emulsify the skin (make into a thick sticky liquid) at the site of contact. Prolonged exposure to a concentrated base may cause deep wounds that are slow to heal. Concentrated bases corrode skin tissue and can cause clouding of the cornea if in the eyes.
One of the following procedures may be used to respond to spills of corrosive materials:
An acid can be neutralized using soda ash or lime. A base can be neutralized with an acidic salt like sodium dihydrogen phosphate or citric acid.
If a corrosive material is splashed into the eyes, the eyes should be flushed using an eye wash station with water for at least 30 minutes. If the exposed person is wearing contact lenses, flush for a few minutes, remove the lenses, and then proceed with more flushing. If a person has swallowed a corrosive material, do not induce vomiting but give "milk of magnesia" (magnesium hydroxide) to neutralize the contents in her stomach. If the corrosive material is on the skin flush with water in a safety shower for 30 min. After all of these cases the person needs to seek immediate medical attention.
In the photographs, below, you can see the effects of corrosive exposure on plain white egg. (Do not attempt this demonstration if you are not a qualified professional expert in this area.) In the demonstration, concentrated Hydrochloric Acid (HCl), Nitric Acid (HNO3), Sulfuric Acid (H2SO4), and 8 M solution (about a 32% solution) of Sodium Hydroxide (NaOH) was added to egg whites to simulate their denaturing effect on proteins. It also approximates the effect of acid or base in the eye.
| Effects on Tissue | ||
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| Plain egg white | After exposure to concentrated HCl | |
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| After exposure to concentrated HNO3 | After exposure to concentrated H2SO4 | After exposure to 8 M NaOH |
Note that the concentrated acids produced an almost "cooked" egg white appearance after about 2 minutes of exposure. Note the yellowing of the egg white with addition of Nitric Acid and the purple fluid that forms with the Sulfuric Acid (noticeable around edges and would be more visible from underneath). The Sodium Hydroxide caused an emulsification that resulted in gelatin-like consistency.
So there you have it. Acids and bases are essential for our quality of life. But they deserve respect and care for their hazards and the harm they can cause.
Molarities of concentrated acids
| About the Author | |
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Wes Adams currently teaches traditional chemistry courses as well as chemistry of hazardous materials to local fire departments. He has a BS in chemistry from the College of Charleston and a MS from University of North Carolina at Wilmington. Organization: Chemistry Department, Asheville Buncombe Community College, 340 Victoria Rd Asheville, NC 28801. Phone: (828) 254-1921 ext 319. |