THE RARER METALS AND THEIR ALLOYS. 501 



without, but from within. I liave, however, ventured to oiler the intro- 

 duction of this lecture in its present form, because any facts which lead 

 us to reflect on the unity of plan in nature, will aid the recognition of 

 the complexity of atomic motion in metals upon which it is needful to 

 insist. 



The foregoing* remarks have special significance in relation to the 

 influence exerted by the rarer metals on the ordinary ones. With the 

 exception of the action of carbon upon iron, probably nothing is more 

 remarkable than the action of the rare metals on those which are 

 more common ; but their peculiar influence often involves, as we shall 

 see, the presence of carbon in the alloy. 



Which, then, are the rarer metals, and how may they be isolated 1 ? 

 The chemist differs somewhat from the metallurgist as to the applica- 

 tion of the word "rare." The chemist thinks of the "rarity" of a 

 compound of a metal; the metallurgist, rather of the difficulty of 

 isolating the metal from the state of combination in which it occurs in 

 nature. 



The chemist in speaking of the reactions of salts of the rarer metals, 

 in view of the wide distribution of limestone and pyrolusite, would 

 hardly think of either calcium or manganese as being among the rarer 

 metals. The metallurgist would consider pure calcium or pure man- 

 ganese to be very rare. I have only recently seen comparatively pure 

 specimens of the latter. 



The metals which, for the purposes of this lecture, may be included 

 among the rarer metals are: (1) Those of the platinum group, which 

 occur in nature in the metallic state; and (2) certain metals which in 

 nature are usually found as oxides or in an oxidized form of some kind, 

 and these are chromium, manganese, vanadium, tungsten, titanium, 

 zirconium, uranium, and molybdenum (which occurs, however, as sul- 

 phide). Incidental reference will be made to nickel and cobalt. 



Of the rare metals of the platinum group I propose to say but little. 

 We are indebted for a magnificent display of them in the library of my 

 friends, Messrs. George and Edward Matthey, and to Mr. Sellon, all 

 members of a great firm of metallurgists. You should specially look at 

 the splendid mass of palladium, extracted from native gold of the value 

 of £2,500,000, at the melted and rolled iridium, and at the masses of 

 osmium and rhodium. No other nation in the world could show such 

 specimens as these, and we are justly proud of them. 



These metals are so interesting and precious in themselves, that I 

 hope you will not think I am taking a sordid view of them by saying 

 that the contents of the case exhibited in the library are certainly not 

 worth less than £10,000. 



As regards the rarer metals which are associated with oxygen, the 

 problem is to remove the oxygen, and this is usually effected either by 

 affording the oxygen an opportunity for uniting with another metal, or 

 by reducing the oxide of the rare metal by carbon, aided by the tearing 



