THE AMALGAMATION OF ORES.

Thames Guardian and Mining Record, Volume I, Issue 244, 20 July 1872, Page 3

THE AMALGAMATION OF ORES.

It has frequently been our duty to call attention to the great loss arising from the imperfect methods, now in use, of extracting gold and silver from their ores ; and the waste has been so extensive, amounting probably to 35 percent, of tho whole of the gold and silver mined since the first discovery of the metals in California, and the inefficient processes are still so much used, that this important subject is always demanding our attention as well as that of miners nnd other persons immediately interested. Much, indeed, remains to ho written and done with regard to tho extraction of these metals before a system, worthy of the present age of metallurgical chemistry, will be generally practised. These considerations give interest to a new utensil and process which not only have the merits of apparent simplicity and adaptability to their purpose, but are recommended to tho mining world by a man having experience and knowledge on this field, whoso communications on this and cognate subjects are known to all readers of tho Scientific American, namely, Mr Percival Stockman, of 322, Grand-street, Williamsburgh, N.Y. The metal mercury still retains its preeminence as a means of obtainnggold and silver by amalgamation; and although the use of zinc is well known, it ischieily employed in combination with or subsequently to the quicksilver treatment. Mr Stockman employs mercury, using specially selected chemicals to expedite the amalgamation, and treats the metalliferous earth in an iron caldron, similar to those used in evaporating cane juice in sugar manufacture. Jliis vessel is intended to be set in brickwork, and to be heated by a lire underneath it. l'iic chaldron has a socket, east on tlio bottom inside, to receive the end of a perpendicular spindle or shaft. Attached to this shaft near the lower end, so as to agitate the contents of the caldron, are three or more fans similar to those of a propeller. Power for driving the shaft is applied by gearing on its upper part. The object of these fans is to keep the pulverised metallic ore in constant motion. The ore is placed in the caldron with sufficient water to make it of a muddy consistency, and the mixture is boiled for fifteen minutes; and then, the ore being diffused in the water by the beat and the fans, mercury is introduced. This metal is immediately, by the same means that separated the* earthy particles of the ore, dispersed into millions of minute globules, and the heat gives these greater facility for attacking the gold concealed in tho

earth. Mr Stockman states that, in the case of ore containing pure metal, the amalgamation described by the above process can be completed in one hour without the use of chemicals. But the valuable metals arc frequently found in combination with the sulpherets of antimony, arsenic, and mercury, and with the pyrites of iron, copper, and argentiferous galena; and it is especially with regard to these more obstinate combinations that a new and thoroughly effective process is desirable. Mr Stockman treats these, in his newly devised apparatus, by the addition of chemical preparations, chiefly chloride of sodium, nitrate of potassa, lime, bisulphuret of carbon, and any of the fixed or volatile oils. The latter is especially needed when orpiment (the sesquisulpliurct of arsenic) is present in combination with the pyrites ; and with a view to rid such ores of the arsenic, the introduction of muriatic acid in connection with sulphuretted hydrogen is recommended. As in the case of the pure ore, the mixture is allowed to boil for fifteen minutes ; the quicksilver is then introduced, and the mass is again boiled for two hours longer. At the expiration of this time a stream of cold water is introduced to precipitate the amalgam ; and the whole mixture is allowed to pass, from an outlet in the bottom of the caldron, to a sluice containing a separator in which tho amalgam is gathered. The amalgam is then ready for the separation of the gold or silver by the evaporation of the mercury in a retort. As it is well known that hardly any two ores are chemically similar, it is obviously impossible to give fixed proportions of the ingredients above mentioned; these quantities must bodetennined by the character and per centages of foreign matters found in combination with the metals.

To the imperfections of the extracting processes now iu use must be attiibuted the disappointment and failures of many of those who go to seek their fortunes in gold and silver mines. Such searchers frequently base their calculations on assays, perhaps scientifically made, of small specimens of the ores ; and tliey have been surprised to find that the ore did not yield, by the old methods, so much as 10, 20, or 50 per cent. This difference discourages the miner, and perhaps induces him to abandon bis operation ; whereas, the fact was simply that the process of the assayer was more efficient than that of the miner.

The importance of tins subject cannot be overrated, and any information that will add to the knowledge already possessed by our readers, many of whom are extensively engaged iu tlie interesting and valuable industries of gold and silver mining will always be received with pleasure by us, ami communicated willingly to the public.— Scientific American.