A SOLVENT OF GOLD.

West Coast Times, Issue 376, 6 December 1866, Page 3

A SOLVENT OF GOLD.

(to the editok of the west coast times.) i Sie — In tho issue of tho " Evening Star" of Friday last I observed uu avtielo, alludiug to a new (?) discovery inado by Mr Roberts, chemist, of Revell 6treet, of a solvent for gold ; aud we are almost given to understand that previous to this aqua regia "was the ouly known Eolvent. JTow, it is a fact well known to every chemist tbat chlorine or oxmurialio gas is a powerful decomposing agent, and acts very readily upon gold. By mixing nitric with hydro-chloric acid (spirits of salt), aqua regia ia formed and cliloriuo evolved j and it is this element that attacks the gold. We are thusnaturally led to the consideration of what is chlorino in its simple state. If equal pnrts of black oxide of manganese and common salt be converted into a paste by the admixture of oil of vitriol, and then placed iv a retort and submitted to tho action of heat, chlorine gas will bo given off which may be easily collected in bottles standing over water in a pneumatic trough. Now, if particles of gold be thrown into one of these bottles, the metal will take fire, aud, by combining with the chlorine, form a chloride of gold precisely similar to that ■which results from tie action of aqua regia upon gold. This is proof sufficient that chlorine alone is the agent which dissolves the gold. Agahi, a mixture of nitric and hydro-chloric acid 9 m the proportion of one to two has long been known as a solvent for gold aud platinum under tbe name of aqua regia. When they are mixed together, the solution instantly becomes yellow, and upon heating it pure chlorine is evolved, and the color of the solution deepens. By continuing the heat, chloric and nitrous acid vapors are disengaged, and after a time the evolution of chlorine gas ceases, and the residual liquid is n solution of hydro-chloric and nitrous acids which is incapable of disolving gold. Henco it is evident that nitric and hydro-chloric acids decompose one another, throwing off chlcrine. "Whilst hydro-chloric and nitrous acids may be heated together without mutual decomposition, it is inferred that tbe poworof nitro-hydro-ehloric acid in dissolving gold is owing to the chlorine liberated. —^Sir Humphrey Davy in the Quarterly Journal, vol. 1.) Chlorine in its simple form is a gas, and in this shape can hardly be used as a solvent. It, however, very readily dissolves in water, forming a solution of a very high solvent power, and has for many years been employed on a large scale in Hungary. There aro other methods of generating chlorine. First, by mixing nitre, common salt, aud sulphuric acid with water. Secondly, by mixing chloride of lime, sulphuric acid, and water. In either case, the solution co formed has the power of dissolving gold. These facts, Mr Editor, were known to chemists many years ago, and I bavo no hesitation in fraying tbat the process of Mr Roberts will be found an exceedingly inconvenient and and unprofitable method of extracting gold from the soil. In the first place we find that tho solution proposed to be used by Mr Roberts contains 97£ per cent, of water, which leaves room for only 2} per cent, of the eolvent, and unless an immense quantity of tbo solution "Has used, tho amount of gold dissolved would bo trifling indeed. This stamps the process as inapplicable in the every day work of the minor, and even if used on an extended scale by companies, the expense of producing chlorine by eiiker of the abovo methods would leave no margin whatever for profit. Hoping you will excuse this trespass on your space, I remain &c, T. R. Pkoctee.