REACTIVITY STUDIES WITH SODIUM AMALGAMS

In the course of systematic studies covering various aspects of the re activity of alkali metal amalgams we report here about first results o n the behaviour of selected sodium amalgams in liquid ammonia. Startin g from the most alkali metal rich amalgam Na3Hg one can show that a st epwise extraction of sodium via Na3Hg2 and NaHg takes place resulting in the final formation of insoluble NaHg2. We discuss how the stepwise extraction of sodium can be correlated to the degree of 'condensation ' of mercury atoms to Hg-n clusters in the sense of a topochemical rea ction. Starting from pure Na3Hg (isolated Hg atoms in a matrix of Na a toms) the successive formation of Na3Hg2 (isolated square Hg-4 cluster s in a matrix of Na atoms), NaHg (one-dimensional zigzag chains of con densed Hg-4 rectangles in a matrix of Na atoms) and NaHg2 (extended th ree-dimensional connection of Hg-4 rectangles) can be traced by X-ray powder methods. NaHg2 and NaHg4 are insoluble in liquid NH3.