Very often chemists need a longer version of reaction arrows (\rightleftharpoons) with the possibility to put text above and below. Analogous to amsmath's \xrightarrow and \xleftarrow this package provides the macro \xrightleftharpoons. The package requires amsmath. To use it, \usepackage{chemarr}, then \xrightleftharpoons[below]{above} .

The package is part of the oberdiek bundle.

The author is Heiko Oberdiek. The package is Copyright © 2001,2006 Heiko Oberdiek.