500 



German Kobald, an evil spirit (akin to the English " goblin "), 

 while the connection between nickel and the chief of evil spirits is 

 obvious. Cobalt continued to justify its name until very 

 recently; only within the last few years have any applications of 

 the metal been discovered. Nickel, on the other hand, has long 

 ago found many uses. 



Cobalt. The metal has a silvery luster, tinged faintly with 

 pink, and does not tarnish. It displaces hydrogen very slowly 

 from dilute acids, but is acted upon rapidly by nitric acid. 



An alloy of cobalt, chromium and tungsten (stellite) is used for 

 high-speed tools. When heated, it keeps its temper better than 

 the steel alloys (p. 493). 



The oxide is used as a pigment in the glass and china industries 

 (p. 362). 



Cobaltous chloride CoCl 2 ,6H 2 is red in color, and when par- 

 tially or wholly dehydrated becomes deep blue. Writing made 

 with a dilute solution of this salt leaves pink traces so faint as to 

 be invisible. But, when the paper is warmed, the hexahydrate is 

 decomposed, and the writing appears blue. When the breath 

 is now blown on the writing, it disappears once more (sympathetic 

 ink). 



Metallurgy of Nickel. Nickel occurs in all iron meteorites. 

 The chief source of nickel is pentlandite, a mixture of nickel, 

 copper and iron sulphides, from Sudbury, Ontario. The ore is 

 roasted and smelted and finally bessemerized (p. 491). The 

 result is an alloy of nickel and copper which is much used for 

 sheet metal work under the name of monel metal. Pure nickel 

 is separated from the copper by an electrolytic process (see copper, 

 p. 515), or by the Mond process (see below). In 1918, more than 

 1,500,000 tons of nickel ore (approximating 3 per cent Ni) were 

 smelted. 



Properties and Uses of the Metal. Nickel is a white, hard, 

 malleable metal which takes, and keeps, a high polish even in 



