Iron amalgam

Iron amalgam cannot be obtained by direct union of the elements. By introduction of a 1 per cent, sodium amalgam into a concentrated solution of ferrous sulphate an iron amalgam is obtained as a viscid mass, which is attracted by a magnet in small pellets. It may also be prepared by triturating powdered iron, mercuric chloride, and water. A more convenient method, perhaps, consists in electrolysing with a very weak current a saturated solution of ferrous sulphate. A bundle of iron wire serves as anode, whilst the cathode consists of platinum foil dipping into a small dish of mercury. The iron amalgamates with the mercury, and at the conclusion of the process excess of the latter element is squeezed out, leaving an amalgam of buttery consistency and containing from 10 to 12 per cent of iron.

Ramann recommends addition of a small quantity of water to a mixture of sodium amalgam and finely divided iron. The product is squeezed to remove excess of mercury, a crystalline amalgam being left which contains 15.75 per cent, of iron and corresponds to the formula Fe₂Hg₃. Iron amalgam blackens both upon exposure to air and water.

When heated, mercury is expelled, and a porous iron left behind. Upon slow oxidation in air ferrous oxide is produced.