1895.] on the Rarer Metals and their Alloys. 501 



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 

 influeuce 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? 

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

 cation 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 manganese to be very rare : 1 have only recently seen com- 

 paratively 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 oxidised 

 form of some kind, and these are chromium, manganese, vanadium, 

 tungsten, titanium, zirconium, uranium and molybdenum (which 

 occurs, however, as sulphide). 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 to 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 ten thousand pounds. 



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 effect of an electric current. In this crucible there is an 

 intimate mixture, in atomic proportions, of oxide of chromium and 



Vol. XIV. (No. 89.) 2 m 



