Gold, Extraction of, by Sodium Amalgam

(Crookes’ Method, Patented.) In the extraction of gold by amalgamation serious difficulties are often occurring through the ‘flouring’ or ‘sickening’ of the mercury employed, and the prevention of the amalgamation by a coating of tarnish on the gold. So much is this the case that lo es of from 30 to 60 per cent. of the gold are usually incurred, and, in many cases a still more serious lo of mercury. When certain minerals, as tellurium compounds, pyrites, ., occur in the gold ore, the mercury is apt, on trituration, to become subdivided into exce ively minute globules, which, owing to their tarnished condition, refuse to unite, and are consequently washed away, it being almost impo ible to separate them from the heavier portions of the ore. This is technically called ‘flouring,’ ‘granulating,’ . Besides this, certain of these minerals affect the mercury in another way, that is, by ‘sickening’ it, or causing it to lose its bright surface and fluidity, and prevents its amalgamating with the gold. Besides the inconvenience and lo thus caused, a further lo of gold takes place from the inability of the ordinary mercury to touch or amalgamate tarnished gold, unle it is ground with it, for a more lengthy period than is found practicable in most cases. Mr Crookes, F.R.S., has, by means of the addition of a certain proportion of sodium, in the form of an amalgam, to the mercury, effectually prevented this serious lo of gold and mercury. By adding certain quantities of amalgams B and C, an amount which, differing from each ore, is ascertained by experiment, the ‘flouring’ and ‘sickening’ of the mercury is effectually prevented, the mercury remaining throughout in the best condition. The addition of about one tenth per-centage of amalgam A, at intervals of some hours, increases most powerfully the affinity of the mercury for the precious metals, and secures a more thorough amalgamation. This invention has met with general approval, and experiments conducted at many mines show its great practical value, giving an increase of from 5 to 30 per cent. in the yield of gold, and, in fact, with many pyrites that yielded no gold to the ordinary amalgamation proce , gave a considerable yield of gold to the sodium amalgamation proce . This has led to its use in most mines, both silver and gold, in America.