METALS AND SOME OF THEIR COMPOUNDS 267 



NICKEL 



This metal is very familiar in the form of nickel plating, and 

 has long been used as an ingredient in the white alloy with 

 copper of which electro-plated dishes, spoons, forks, and other 

 table furniture are made. But the very interesting and remark- 

 able process by which a large proportion of the pure metal is 

 made is based on a modern discovery which dates back no further 

 than 1890. In that year a paper in the Transactions of the 

 Chemical Society, by the late Dr. Ludwig Mond, associated with 

 Dr. C. Langer and Dr. F. Quincke, announced the discovery of 

 the fact that when metallic nickel, especially in a finely divided 

 state, is heated gently in a stream of carbon monoxide gas a 

 volatile compound is formed which consists of the metal in 

 union with carbon monoxide. The escaping gas burns with a 

 brightly luminous flame, and when heated to a temperature about 

 180 it is resolved completely into the gas and the metal, the 

 latter being deposited in the form of a lustrous mirror-like solid. 

 When the mixture of gases is passed through a glass tube sur- 

 rounded by a freezing mixture of ice and salt the compound is 

 condensed to a colourless, mobile liquid, a little heavier than 

 water, and boiling at 43 C. The liquid has the formula Ni(CO) 4 ; 

 it is not acted on by acids or alkalis. It precipitates copper and 

 silver from ammoniacal solutions of the chlorides of those metals, 

 but in general it behaves as a neutral compound. Attempts have 

 been made to obtain compounds of the same order from the metals 

 nearly allied to nickel, but no success has been met with in the 

 case of cobalt. Iron and platinum have been found to yield 

 carbonyl compounds, but with greater difficulty, and the com- 

 pounds formed are much less volatile than nickel carbonyl. 



It is easy to see how these observations may be turned to 

 account in the extraction of nickel from the mixed ores from 

 which so much of this metal has been obtained. The ores which 

 contain a number of metals, iron, copper, cobalt, nickel, etc., in 

 the form of sulphide and arsenide are first roasted, by which the 

 greater part of the sulphur and arsenic is expelled and the metals 

 converted into oxides. These are then heated moderately in a 

 stream of producer gas whereby the oxides are reduced to the 

 metallic state, and the temperature being duly regulated, the 

 carbonic oxide in the gas unites with the metallic nickel and 

 carries it off, while the other metals which form no volatile com- 



