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Medical Term:

Hofmeister series

Pronunciation: hof′mī-stĕr

Definition: the series of cations Mg2+, Ca2+, Sr2+, Ba2+, Li+, Na+, K+, Rb+, Cs+, and of anions citrate3−, tartrate2−, SO42−, acetate−, NO3−, CIO3−, I−, CNS− (among others), each series arranged in order of decreasing ability to: precipitate the dispersed substance of lyophilic sols; “salt out” organic substances (aniline, ethyl acetate) from aqueous solutions; or inhibit the swelling of gels. These effects, among other related ones, are ascribable to the abstraction and binding of water by these ions (hydration), which also decreases in the orders given, so that (in the monovalent cation series) Li+, with the smallest crystal radius, has the largest hydrated radius, and vice versa for Cs+.

Synonym(s): lyotropic series

[Franz Hofmeister]