Buffering Agent Information
A buffering agent is a weak acid or base used to maintain the acidity (pH) of a solution at a chosen value. The function of a buffering agent is to prevent a rapid change in pH when acids or bases are added to the solution. Buffering agents have variable properties—some are more soluble than others; some are acidic while others are basic. As pH managers, they are important in many chemical applications, including agriculture, food processing, biochemistry, medicine and photography.
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What is a buffering agent
A buffering agent can be either a weak acid or weak base. Buffering agents are usually added to water to form a buffer solution, which maintains a stable pH in spite of other acids and bases being combined with it. For example, buffered aspirin has a buffering agent, such as MgO, that will maintain the pH of the aspirin as it passes through the acidic stomach of the patient. Another use of a buffering agent is in an antacid tablet, whose primary purpose is to lower the acidity of the stomach.
How a buffering agent works
The way buffering agents work is seen in how buffer solutions work. Using the Henderson-Hasselbalch equation we get an equilibrium expression between the acid and conjugate base. As a result we see that there is little change in the concentrations of the acid and base so therefore the solution is buffered. A buffering agent sets up this concentration ratio by providing the corresponding conjugate acid or base to stabilize the pH of that which it is added to. The resulting pH of this combination can be found by using Le Chatelier's principle:
where HA is the weak acid and A is the anion of the base.
Examples
Agriculture
Monopotassium phosphate (MKP) is an example of a buffering agent. It has a mildly acidic reaction; when applied as a fertilizer with urea or diammonium phosphate, it minimizes pH fluctuations which can cause nitrogen loss and simultaneously provides potassium nutrient.
In humans
Buffering agents in humans, functioning in acid base homeostasis, are extracellular agents (e.g., bicarbonate, ammonia) as well as intracellular agents (including proteins and phosphate). A dilute mixture of monosodium phosphate and disodium phosphate can be made to approach physiological pH and can serve as an agent for phosphate loading or colonic lavage.
Shampoos and detergents
Most shampoos are buffered so that they are slightly alkaline. The buffer counteracts the alkalinity of soap. If either of these substances become too acidic or too alkaline, they could damage fabric, and/or skin and hair.
See also
References
- Atkins, Peter; Jones, Loretta (2005). Chemical Principles: The Quest for Insight (Third ed.). New York: Freeman. ISBN 071675701X.
- Harris, Daniel C. (2003). Quantitative Chemical Analysis (Sixth ed.). New York: Freeman. ISBN 0716744643.
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