864.] CALVERT ON THE EXTRACTION OF GOLD. 457 



the mixture of hydrochloric acid and peroxide of manganese, or of 

 sulphuric acid, peroxide of manganese, and chloride of sodium, to 

 remain for twelve hours in contact with the auriferous sand ; and, 

 then, instead of washing-out the solution of gold, I added a small 

 quantity of water, which removed a part of the acting agent, and 

 this was made to percolate several times through the sand ; by 

 which method I succeeded in extracting from the sand, within a 

 fraction the whole of the gold. I then, repeated the last experi- 

 ments with natural auriferous quartz, and easily extracted the two 

 ounces of gold per ton which it contained. I therefore propose 

 the following plan for extracting the gold on a commercial scale : — 

 The finely-reduced auriferous quartz should be intimately mixed 

 with about one per cent of peroxide of manganese ; and if com- 

 mon salt be used this material should be added at the same time 

 as the manganese, in the proportion of three parts of salt to two 

 of manganese. The whole should be then introduced into closed 

 vats, having false bottoms, upon which is laid a quantity of small 

 branches covered with straw, so as to prevent the reduced quartz 

 from filling the holes in the false bottom. Muriatic acid should 

 then be added if manganese alone is used, and diluted sulphuric 

 acid if manganese and salt have been employed ; and, after having 

 left the whole in contact for twelve hours, water should be added so as 

 to fill-up the whole space between the false and true bottoms with 

 fluid. This fluid should then be pumped-up and allowed to per- 

 colate through the mass ; and after this has been done several times, 

 the fluid should be run off into separate vats for extracting the 

 gold and copper that it may contain. To effect this, old iron is placed 

 in it to precipitate the copper ; and after this has been removed, the 

 liquor is heated to drive away the excess of free chlorine, and a con- 

 centrated solution of sulphate of protoxide of iron, or green copperas, 

 must be added, which, acting on the gold-solution, will precipitate 

 the gold in a metallic form. By this method, both gold and copper 

 are obtained in a marketable condition. If silver is present in the 

 ore, a slight modification in the process will enable the operator to 

 >btain this metal also. It is simply necessary to generate the 

 chlorine of the vitriol, manganese, and chloride of sodium process, 

 taking care to use an excess of salt, that is, six parts instead of 

 three, as above directed. The purpose of this chloride of sodium 

 being to hold in solution any chloride of silver that may have been 

 formed by the action of chlorine on the silver-ore, and to extract 

 the metal, the following alteration in the mode of precipitation is 



