D. CHEMISTRY AND METALLURGY. 53 



acid is useful, and the copper in this way becomes converted 

 into a soluble chloride. 5 A, October, 1870, 424. 



REDUCTION OF ORES BY CHLORIDE OF IRON. 



A method of reducing ores by means of chloride of iron has 

 recently been patented, which is specially adapted to the ex- 

 traction of metals alloyed with sulphur, arsenic, or antimony. 

 The process depends upon the fact that chloride of iron, in 

 the presence of air and water, readily decomposes sulphur, 

 arsenic, and antimonial combinations, iron or copper pyrites, 

 the sulphurets of cobalt, nickel, sulphuret of antimony, lead, 

 silver, etc. The chloride of iron is reduced to chloruret of 

 iron, and the metals transferred into chlorides, the chloruret 

 of iron being* again changed to chloride by the influence of 

 the oxygen of the atmosphere, etc. If among the ores to be 

 manipulated there be too little sulphur, it is well to add, 

 from time to time, a little free acid, such as nitric, in order to 

 assist the reconstitution of the chloride of iron. With iron 

 or copper pyrites it is only necessary to add common salt, 

 since the sulphur of the ore is oxidized by means of the chlo- 

 ride of iron and atmospheric air, with the result of producing 

 sulphate of iron or sulphate of copper. 13 C, 1871, Jime 1, 

 11., 714. 



COLOROMETRIC DETERMINATION OF GOLD IN QUARTZ. 



A process for the colorometric estimation of the quantity 

 of gold in quartz has been submitted by Mr. Skey, of the gov- 

 ernment laboratory, to the Philosophical Society of Welling- 

 ton, New Zealand, which is said to meet all requirements 

 without the necessity of using quicksilver. The stone to be 

 estimated, after having been thoroughly crushed and calcined, 

 is immersed in a bath of iodine or bromine, and permitted to 

 stand for some time. Slips of Swedish filtering-paper are 

 then dipped in the fluid and dried alternately until the paper 

 is thoroughly saturated, after which they are burned in a 

 muffle. If no gold be present the ashes will be white, but 

 one pennyweight to the ton will give them a beautiful pur- 

 ple color. It is believed that further experiments, with io- 

 dine or bromine baths, of known contents of gold, will enable 

 the exact proportion of gold to be tested by the colorometric 

 method. 8 A, October 1,181. 



