Fire assaying, in essence, is a miniature or small scale smelting process which recovers and reports the total gold content of the assay sample, including gold combined with other elements or locked in the ore particles. Because of this, a assay may report values that cannot be recovered by placer methods and it cannot be … Read more
The Gold Refining Process by Aqua Regia was introduced at the Pretoria Mint after the Miller process had been tried and abandoned owing to the alleged difficulty of treating the gold bullion extracted by the cyanide process. In the aqua regia process the gold is dissolved and precipitated. It is made very difficult if the … Read more
The Moebius Process of Purification of Gold by Electrolysis is now in successful operation and is said to be specially suitable for refining copper bullion containing large proportions of silver and gold with small quantities of lead, platinum, and other metals, but is chiefly used in parting dore silver containing not more than 20 per 1,000 … Read more
The guard pot, with the clay pot in it containing 2 or 3 ozs. of fused borax, is placed in the furnace, and is heated gradually until the bottom of the clay pot is dull red. The ingots (of which the larger are slipper-shaped) to be refined, amounting in all to 650 to 720 ozs. … Read more
The use of chlorine gas for the purification of molten gold was first proposed by L. Thompson, and the results of his investigations were published in the Journal of the Society of Arts two years later. He stated that “ it has long been known to chemists, that not only has gold no affinity to … Read more
This Gutzkow Process of parting by sulphuric acid was invented and patented by Mr. F. Gutzkow. It has been extensively worked in Germany and in San Francisco, and up to the year 1891 had been instrumental, on the authority of Mr. Gutzkow, in refining one hundred million dollars’ worth of silver. It is fully described in … Read more
This process has now, in the majority of refineries, superseded the nitric acid method, which is much more expensive, owing to the higher cost of the acid used and of the plant required. The German chemist, Kunckel, who lived in the seventeenth century, is said to have been the first to employ sulphuric acid in … Read more
The silver chloride is then reduced in lead-lined tanks by means of granulated zinc and water acidulated with sulphuric acid. Thirty-three pounds of commercial granulated zinc are stated to be enough to reduce 100 lbs. of silver from the chloride. The reactions involved are as follows: 2AgCl + Zn = ZnCl2 + 2Ag Zn + … Read more
The gold to be parted must be approximately free from base metals, particularly from those which are not soluble in nitric acid, such as tin, arsenic, antimony. If these were present they would form insoluble oxides, which would remain with the gold, so that further refining operations would be necessary: they would, moreover, cause a … Read more
Parting is the separation of silver from gold and a process during which the base metals are separated from both, but, as the presence of a high percentage of these base metals is injurious to the successful conduct of the processes which are chiefly in use, a preliminary refining by one of the methods already … Read more