The transfer and withdrawal of small amounts of blood that is repeated until the blood volume is almost entirely exchanged: "Exchange transfusions are used for infants who are born with hemolytic disease (the abnormal breakdown of red blood cells) and in patients with uremia (a form of blood poisoning caused by the accumulation in the blood of products that are normally eliminated in the urine)."

1. A chemical reaction in which ions are interchanged between one substance and another; usually by means of passing a liquid through a porous, granular solid ghat is relatively insoluble.
2. The use of such a process to replace certain selected anions or cations in a solution; for example, to remove undesirable substances, as in water softening, or to recover desirable ones, as in the separation of valuable metals from wastes.
3. The interchange of ions of the same charge between a solution and a solid in contact with it.
4. A reversible chemical reaction between an insoluble solid and a solution during which ions may be interchanged, used in water softening and in the separation of radioactive isotopes.
5. A chemical reaction in which mobile hydrated ions of a solid are exchanged, equivalent for equivalent, for ions of like charge in solution.

The solid has an open, fish-net-like structure, and the mobile ions neutralize the charged, or potentially charged, groups attached to the solid matrix.

The solid matrix is termed the ion exchanger.

1. A separation technique using a resin (stationary phase), which may be basic or acidic, to bind ionized solutes (mobile phase) reversibly.
2. A chromatographic procedure in which the stationary phase consists of ion-exchange resins which may be acidic or basic.
3. The process of separating and analyzing different substances according to their affinities for chemically stable but very reactive synthetic exchanges, which are composed largely of polystyrene cellulose.

The process uses an absorbent containing ionizing groups and accommodates the exchange of ions between a solution of substance to be analyzed and the absorbent.

Ion exchange chromatography is often used to separate components of nucleic acids and proteins elaborated by various structures throughout the body.

Different ions deposited in the absorbent during the exchange produce bands of different colors, which constitute a chromatograph.

Fuel cell which operates on hydrogen and oxygen in the air, similar to the standard hydrogen-oxygen fuel cell with the exception that the liquid electrolyte is replaced by an ion-exchange membrane.

Operation is at atmospheric pressure and room temperature.

1. Any of a number of (usually organic) materials that are capable of exchanging the included ions with ions in a surrounding solution; used for deionizing water or for chromatography (technique of separating and analyzing the components of a mixture of liquids or gases) of organic molecules.
2. Synthetic organic substances of high molecular weight which are used to replace certain negative or positive ions that they encounter in solutions.
3. A polymeric resin that contains electrically charged fragments (fixed ions) permanently attached to the polymer backbone, electrical neutrality is achieved by attached mobile "counterions" in the solution phase the resin is immersed into.

A practical use of such resin is the removal of unwanted ions from a solution by replacing them with other ions; for example, a cation exchange resin containing fixed negative charges with attached mobile sodium ions can be used to remove "hardness" from water if the calcium and magnesium ions are more strongly attracted to the resin and therefore will replace the sodium ions.

Eventually all the sodium ions will go into solution and the ion-exchange process terminates; then, resin can be regenerated by soaking in a high concentration sodium salt solution.

Such a process can also be used to remove unwanted ions from polluted water streams.

More about ion-exchange resins

When immersed in a solution, the resins absorb the solution and swell; the degree of swelling is dependent on the polymeric structure and the total ion concentration of the solution.

Resins of suitable chemical compositions and physical properties may be synthesized at will for specific ion-exchange applications; thus, they comprise the bulk of synthetic ion-exchange materials used in the laboratory and industry.

In industrial and domestic applications, ion-exchange resins are used for the removal of calcium, magnesium, iron, and manganese salts from water (water softening), for purification of sugar, and for concentration of valuable elements; such as, gold, silver, and uranium from mineral ores.

In chemical analysis, ion-exchange resins are used for the separation or concentration of ionic substances, and in chemical synthesis, some ion-exchange resins have been used as effective catalysts, notably in esterification and hydrolysis reactions.

Types of ion-exchange resins

Two separate types of resins are commonly classed as ion-exchange resins, although their functions do not involve an interchange of ions.

These are the chelating resins and the electron-exchange resins.

• Chelating resins are styrene-divinylbenzene polymers to which iminodiacetate groups are introduced. This functional group forms complexes with all the metallic elements except the alkali metals, with stabilities that vary with the different metals; in analytical chemistry, they are used for the separation of trace amounts of metals.
• Electron-exchange resins accept or donate electrons to the surrounding solution and are used in oxidation-reduction reactions; examples include polymers prepared from hydroquinone, phenol, and formaldehyde.