buffer

buffer1
/buf"euhr/, n.
1. an apparatus at the end of a railroad car, railroad track, etc., for absorbing shock during coupling, collisions, etc.
2. any device, material, or apparatus used as a shield, cushion, or bumper, esp. on machinery.
3. any intermediate or intervening shield or device reducing the danger of interaction between two machines, chemicals, electronic components, etc.
4. a person or thing that shields and protects against annoyance, harm, hostile forces, etc., or that lessens the impact of a shock or reversal.
5. any reserve moneys, negotiable securities, legal procedures, etc., that protect a person, organization, or country against financial ruin.
6. See buffer state.
7. Ecol. an animal population that becomes the prey of a predator that usually feeds on a different species.
8. Computers. a storage device for temporarily holding data until the computer is ready to receive or process the data, as when a receiving unit has an operating speed lower than that of the unit feeding data to it.
9. Electronics. a circuit with a single output activated by one or more of several inputs.
10. Chem.
a. any substance or mixture of compounds that, added to a solution, is capable of neutralizing both acids and bases without appreciably changing the original acidity or alkalinity of the solution.
b. Also called buffer solution. a solution containing such a substance.
v.t.
11. Chem. to treat with a buffer.
12. to cushion, shield, or protect.
13. to lessen the adverse effect of; ease: The drug buffered his pain.
[1825-35; BUFF2 + -ER1]
buffer2
/buf"euhr/, n.
1. a device for polishing or buffing, as a buff stick or buff wheel.
2. a worker who uses such a device.
[1850-55; BUFF1 + -ER1]
buffer3
/buf"euhr/, n. Brit. Slang.
1. a foolish or incompetent person.
2. a fellow; man.
3. a chief boatswain's mate in the British navy.
[1680-90; orig. uncert.]

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Solution usually containing a weak acid and its conjugate weak base, or a salt, of such a composition that the pH is held constant within a certain range.

An example is a solution containing acetic acid (CH3COOH) and the acetate ion (CH3COO-). The pH depends on their relative concentration and can be found with a simple formula involving their ratio. Relatively small additions of acid or base will change the concentration of the two species, but their ratio, and hence the pH, will not change much. Different buffers are useful in different pH ranges; they include phosphoric acid, citric acid, and boric acid, each with their salts. Biological fluids such as blood, tears, and semen have natural buffers to maintain them at the pH required for their proper function. See also law of mass action.

* * *

 in chemistry, solution usually containing an acid and a base, or a salt, that tends to maintain a constant hydrogen ion concentration. Ions are atoms or molecules that have lost or gained one or more electrons. An example of a common buffer is a solution of acetic acid (CH3COOH) and sodium acetate. In water solution, sodium acetate is completely dissociated into sodium (Na+) and acetate (CH3COO-) ions. The hydrogen ion concentration of the buffer solution is given by the expression:

      in which Ka is the ionization constant of acetic acid and the expressions in brackets are the concentrations of the respective substances. The hydrogen ion concentration of the buffer solution is dependent on the relative amounts of acetic acid and acetate ion (or sodium acetate) present, known as the buffer ratio. The addition of an acid or a base will cause corresponding changes in the concentration of acetic acid and acetate ion, but as long as the concentration of the added substances is small compared to the concentration of the individual buffer components, the new hydrogen ion concentration will remain close to its original value.

      Buffer solutions with different hydrogen ion concentrations may be prepared by varying the buffer ratio and by choice of an acid of appropriate intrinsic strength. Buffer solutions commonly used include phosphoric, citric, or boric acids and their salts.

      Because acids and bases tend to promote a wide range of chemical reactions, the maintenance of a certain level of acidity or alkalinity in a solution through the use of buffer solutions is essential to many chemical and biological experiments. Many biochemical processes occur only at specific pH values, which are maintained by natural buffers present in the body.

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Universalium. 2010.

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