Action of charcoal upon a solution of gold chloride

✍ Scribed by George A. Koenig

• Publisher: Elsevier Science
• Year: 1882
• Tongue: English
• Weight: 140 KB
• Volume: 113
• Category: Article
• ISSN: 0016-0032
• DOI: 10.1016/0016-0032(82)90314-3

✦ Synopsis

Among the substances which decompose gold solutions, the textbooks-and, as far as I could find, the special literature-do not mention charcoal. This property of charcoal has become the subject of a United States patent, claiming that by filtering liquids containing in solution gold and certain metallic salts, the gold alone would be precipitated upon the charcoal, and none of the other metals. In the spring of 1880 my attention was drawn to this subject, and, as the fad appeared unquestionable, it became of some interest to ascertain the reactions involved.

The following possibilities suggested themselves :

1. Gold might be precipitated by the alkaline carbonates of the ash mixed with the charcoal from the charring process.

2. Gases condensed in the coal might act as reducing agents.

3. The action might be physical only, belonging to the so-called Malytic phenomena.

4. Carbon might be oxidized by auric chloride and water, either to carbon monoxide or dioxide.

Gold hexachloride was prepared as nearly free from uncombined chlorine as several evaporations to dryness could make it.

Charcoal was broken into pieces, and, by sifting, assorted to an average diameter of about & of an inch.

It was then digested with hydrochloric and hydrofluoric acids for 12 hours, and washed first with dilute acid, then with distilled water until the h&r ceased to act upon blue litmus. After drying, the charcoal was kept at a full red heat for one hour in a closed crucible. Any action produced by this purified material upon gold solution could not be ascribed to inorganic constituents.