![]() #Precipitate gold free#In these experiments the minerals were selected so as to be as free as possible from admixtures of other minerals. Experiments With Silver Sulphate Solution Such methods of study may prove useful in determining the relative efficiency of various minerals in reactions of the type described in this paper, but careful analytical studies are essential to their apprehension and for the present appear to form a more profitable line of research. ![]() As a consequence, by measuring the relative strengths of the currents developed when various sulphides are successively connected as parts of a galvanic circuit, it is possible to obtain a measure of the relative rate at which oxidation or reduction takes place. It is now recognized that most reactions of oxidation and reduction may be effected by the use of the electric current in place of chemical agents, and, conversely, that an electric current may readily be produced by a proper arrangement of the components of any one of these reactions. The potentials in metallic salts solutions depend entirely upon the nature and concentrations of the solutions.” These writers have arranged the commoner metallic minerals in the order of the electrical potentials developed when they are in contact with a conducting liquid, and Wells concludes that “ such potentials simply measure in an electrical way the oxidizing power of the solutions, the mineral playing a very insignificant part. This line of research has recently been followed by Gottschalk and Buehler and E. His work appears until recently to have escaped the attention of economic geologists it blocked out, however, one of the most interesting and promising fields of research in the science of ore deposits.Īnother line of investigation inaugurated by Skey involves the measurement of the electrical potentials developed when two metallic minerals are connected as poles of a galvanic circuit and immersed in some conducting liquid which does not react actively with them. Skey, printed in 1871 in a New Zealand publication. The earliest important work on the precipitation of gold and silver by metallic minerals was that of W. Geological Survey but as the phenomena seem to have an important application in the science of ore deposits, particularly in secondary enrichment, it has been thought best to outline the field of investigation in this preliminary paper and to make the main results immediately available to economic geologists. Quantitative studies of the reactions with other minerals are now in progress in the laboratory of the U. The tests made with most of the minerals were qualitative only, but the reactions of a silver sulphate solution on chalcocite and niccolite were submitted to quantitative study to determine the nature of the reactions involved. When similar experiments are conducted with other sulphides and with certain arsenides and sulph-arsenides, especially those known to be commonly associated with native silver in ore deposits, it is found that these minerals differ greatly in their efficiency as precipitants, especially in their effect on silver solutions. If a piece of chalcocite is hung in a dilute aqueous solution of silver sulphate (1/40 normal), a coating of silver begins immediately to form on the mineral, and within a few moments a beautiful silver tree has developed, similar to that formed when metallic zinc is immersed in a similar solution. ![]() The color of the solution changes from yellow to pale green, showing that copper is dissolved simultaneously with the precipitation of metallic gold. of a dilute solution of gold chloride are poured over it, two or three shakes of the tube suffice to remove all the gold from the solution. If a little finely powdered chalcocite is placed in a test-tube and 2 or 3 cc. While the reducing action of organic matter, of ferrous sulphate, and of hydrogen sulphide has frequently been invoked to account for the deposition of native gold and silver from ore-forming solutions, the high efficiency in this respect of certain of the metallic minerals which form the ore itself has not been sufficiently recognized. How Metallic Minerals Affect Silver and Gold Precipitation.Associations of Native Gold with Sulphides. ![]()
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