932 Transactions of the American Institute. 



easily volatile metals, such for instance as gold and arsenic, bismuth, 

 antimony, all of which form alloys with it, and change the point 

 of volatilization. 



For instance, arsenide of gold, a gray brittle aWoj, is easily 

 fusible, and does not give up all its arsenic even when fused for 

 tAvo hours in an open crucible. 



8P0XGE GOLD. 



Dr. C. T. Jackson, of Boston, discovered the manufacture of 

 sponge gold, capable of welding while cold, by adding to a con- 

 centrated solution of chloride of gold a small quantity of oxalic 

 acid, and then a sufficient quantity of potash, or cai'bonate of 

 potash, to dissolve nearly all the oxide of gold, and then adding a 

 large quantity of crystalized oxalic acid, and boiling the solution. 

 All the gold is thrown down as a spongy mass, which, on being 

 washed, is quite pure, and when pressed or hammered, becomes 

 quite solid. {^Am. Journal Science (2) 6-187.) 



The action of electricity on different solutions of gold is very 

 interesting. Among other phenomena of less importance, I will 

 here mention that electricity can be used for dissolving gold in salt 

 water in presence of peroxides. The chloride of sodium is decom- 

 posed, and the chlorine siezes upon the gold and forms a soluble 

 salt, while the sodium oxidizes and forms soda. 



The various methods of working gold ores can be divided into 

 three classes, the mechanical, the chemical; and the mixed, combining 

 the use of both methods. 



EXTKACTION OF GOLD. 



The mechanical method is certainly the simiDlest, and consists 

 in crushing the ore to powder, by means of stamps or crushing- 

 machines, and in extracting the gold by means of amalgamating 

 the precious metal with quicksilver or mercury. The more perfect 

 the crushing and pulverizing process, the better, of course, is also 

 the result obtained by the amalgamation. The crushing of ore is 

 mostly done by the well-known old-fashioned stamp-mills. Some 

 use steam or compressed air stamps; some adopt Whelpley and 

 Storer's centrifugal crusher and pulverizer, all of which seem 

 to be improvements on the old stamp-mill, and certainly work well 

 where they are in good hands and connected with machine shops 

 and founderies. A new crusher (Wagner's patent) is now on exhibi- 

 tion in this city, and works as well as any other I have yet seen. 

 The principal feature of this machine is the ingenious manner of 



