Year: 1876

Although most miners recognize the fact that gold in fine particles will float or remain for some time suspend ed in water, few know why this is SO as it seems contrary to the principles of gravitation. A series of expert ments made long time since by one competent to judge, proved, first, that fine gold would reman atlOat in com

 mon temperature for over 24 hours and, secoLd, that when the temperature of the water was raised to, or near to, the boiling point, the suspended parti. cles of gold would subside. Reflecling on these points, the experimenter was reminded of the well-known property possessed by platinum of condensing gases upon its surface, and it seemed no far fetched hypothesis to assume that gold and, probably, most other metals, possessed the same property, though in a less degree Upon this suppOsitiOn, the fact that particles of gold did not sink in water in accord ance with their specific gravity was readily explained, because the buOyan- cy of the film of air or other gas ad- herring to them would more or less cOunteract their weight, and as the surface of bodies relatively increases as their bulk decreases, it was plain that the smaller the particle of gold the more apt it must be to be kept atioat by film of gas upon the surface. It also becomes obvious that when the water is heated 10 a certain degree, the particles of gold suspended therein must subside, because the film of gas sustaining them would be expanded and removed.

 On this peculiar characteristic of metals to cOndense gases, Overman may be cited as an authority (Metal- lurgy, D. 2S2), As not only the spe- cific gravity, but the size of gram and its affinity for water and other miner als, has a decided influence on its ten dency to subside, it is evident that the operation of separating minerals is truly one which requires more than common intelligence to perform it well. Iron is by far specifically heavier than quartz, still fine iron filings will float iu water. while fine sand sinks directly. Carbon has not the weight of clay, ye: carbon sinks sooner in water than clay, but not SD in air. Gold is by far heavier than sileX, but we may observe, by means of a mIcros- cope, a multitude of fine particles of gold suspended in water, while we cannot detect the slightest particle of silicious matter, however fine IL may be. The latter will subside more quickly than visible particles of heavy gold. All the metals appear tO have d tendency to float on water when in fine particles, some more than others. This is caused by particle of gas, either air or water, adhering tO the particle of metal, which causes it to be light and float or become suspended. Pre- ciOus metals appear to possess more of this quality than others. Sulphurets of metals. oxides, salts and. in fact, all compound matter. do not manifest 1t. The size 0t a particle and it's form have also some influence in causing heavy matter to subside in water; a large grain will, in all instances, sink faster than a small one"

 Unless we accept the explanation that a great deal of gold escapes with the water, despite its high specific gravity, It will be difficult to account Tor the loss in working with a continu- ouS current from the stamps. We our selves had some extremely fine gold in bottle of water, not long since, and, as a matter of curiosity, shook 1t up and set it on the desk to see how long II would take before settling. On the second morning minute particles could still be seen suspended in the water, although the water had been perfectly quiet in the meantime.