buffer

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A solution selected or prepared to minimize changes in hydrogen ion concentration which would otherwise tend to occur as a result of a chemical reaction. In general, chemical buffers are systems which, once constituted, tend to resist further change due to external influences. Thus it is possible, for example, to make buffers resistant to changes in temperature, pressure, volume, redox potential, or acidity. The commonest buffer in chemical solution systems is the acid-base buffer.

Chemical reactions known or suspected to be dependent on the acidity of the solution, as well as on other variables, are frequently studied by measurements in comixture with an appropriate buffer. For example, it may be desirable to investigate how the rate of a chemical reaction depends upon the hydrogen ion activity (pH). This is accomplished by measurements in several buffer systems, each of which provides a nearly constant, different pH. Alternatively, it may be desirable to measure the effects of other variables on a pH-sensitive system, by stabilizing the pH at a convenient value with a particular buffer. See also pH.

Buffer action depends upon the fact that, if two or more reactions coexist in a solution, then the chemical potential of any species is common to all reactions in which it takes part, and may be defined by specification of the chemical potentials of all other species in any one of the reactions. To be effective, a buffer must be able to respond to an increase as well as a decrease of the species to be buffered. In order to do so, it is necessary that the proton transfer step of the buffer be reversible with respect to the species involved, in the reaction to be buffered. In aqueous solution the proton transfer between most acids, their conjugate bases, and water, is so rapid and reversible that the dominant direct source of protons for a chemical reaction is H₃O⁺, the hydronium ion.

Buffers are particularly effective in water, because of the unusual properties of water as a solvent. Its high dielectric constant tends to promote the existence of formally charged ions (ionization). Because it has both an acidic (H) and a basic (O) group, it may form bonds with ionic species leading to an organized sheath of solvent surrounding an ion (solvation). Water also tends to self-ionize to form its own conjugate acid-base system. See also Acid and base; Acid-base indicator; Ionic equilibrium; Solvation.

A reserved segment of memory used to hold data while it is being processed. In a program, buffers are created to hold some amount of data from each of the files that will be read or written. In a streaming media application, the program uses buffers to store an advance supply of audio or video data to compensate for momentary delays.

With regular computer applications, buffers are allocated and deallocated from the general memory pool. In printers and other hardware devices, buffers can be small memory banks used for just one temporary storage function. See buffering, double buffering, buffer overflow, buffer flush and bucket.

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Substances that counteract rapid or wide pH changes in a solution.

1. A device, apparatus, or material which reduces mechanical shock due to impact.
2. A device located at the bottom of an elevator hoistway, designed to stop a car or counter-weight from descending beyond its normal limit of travel; motion beyond this limit is taken up by storing or by absorbing and dissipating the kinetic energy of the car or counterweight. Also see oil buffer, spring buffer.
3. Any type of barrier that limits the scattering of rock as a result

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In chemistry, the components of a solution that can neutralize either an acid or a base and thus maintain a constant pH.