Amalgam (chemistry)

Formerly the zinc plates of dry batteries were amalgamated with a small amount of mercury to prevent deterioration in storage.

Sodium amalgam is produced as a byproduct of the chloralkali process and used as an important reducing agent in organic and inorganic chemistry.

With water, it decomposes into concentrated sodium hydroxide solution, hydrogen and mercury, which can then return to the chloralkali process anew.

It remains soft for a short time so it can be packed to fill any irregular volume, and then forms a hard compound.

The use of mercury in 19th century placer mining in California, now prohibited, has caused extensive pollution problems in riverine and estuarine environments, ongoing to this day.

Sometimes substantial slugs of amalgam are found in downstream river and creek bottoms by amateur wet-suited miners seeking gold nuggets with the aid of an engine-powered water vacuum/dredge mounted on a float.

Amalgam obtained by either process was then heated in a distillation retort, recovering the mercury for reuse and leaving behind the gold.

As this released mercury vapors to the atmosphere, the process could induce adverse health effects and long term pollution.

Today, mercury amalgamation has been replaced by other methods to recuperate gold and silver from ore in developed nations.

The presence of these salts in water can be detected with a probe that uses the readiness of mercury ions to form an amalgam with copper.

A nitric acid solution of salts under investigation is applied to a piece of copper foil, and any mercury ions present will leave spots of silvery-coloured amalgam.