142 



DISCOVERY 



light when rendered incandescent with heat. Search 

 was therefore made to discover other minerals in 

 which this rare metal occurred in quantities plentiful 

 cnougli to start an industry. The Germans were not 

 long before they discovered a sand on the sca-shorc 

 of Brazil which answered the purpose exactly. This 

 was monazite, which consists chiefly of a phosphate 

 of a rare metal, cerium ; but it also contained about 

 6 per cent, of the thorium, the metal of which they were 

 in need. The story of how the Germans succeeded 

 in getting the monopoly of the monazite of practically 

 the whole world is a very interesting one, but we have 

 not the space to tell it here ; suffice to say that the 

 outbreak of war in 1914 put an end to this state of 

 things, and secured for Great Britain the use of her 

 own supplies from Southern India and Ceylon. The 

 thorium was extracted from the sand, and Auer von 

 Welsbach, after numberless experiments, found out 

 how to make the gas-mantles which are so common 

 a feature of eveiy home. These mantles consist of 

 99 per cent, thorium oxide and only i per cent, cerium 

 oxide, these proportions yielding the brightest light. 

 The problem therefore arose how to use up the waste 

 cerium and the other rare elements, such as didymium, 

 associated with it. A use was found for a very small 

 quantity of didymium for printing the trade mark 

 on the mantles, the oxide of this metal showing up 

 pink on the white background of the mantle. But 

 this small quantity had in no way solved the problem, 

 when Welsbach noticed that, if all these metals were 

 reduced together to the metallic state, he obtained 

 a mix metal which when struck against steel emitted 

 bright sparks ; in this discovery we have the origin 

 of the countless pyrophoric alloys which can be bought 

 to-day either as cigarette-lighters or as contrivances 

 with which to light the kitchen gas-ring. These mix 

 metals or pyrophoric alloys are now being manu- 

 factured in huge quantities at a quite reasonable 

 figure in America and elsewhere. 



The rare metals have, however, served in another 

 way to make life brighter for us : of the countless 

 electric bulbs which illumine our dwelling-houses 

 and offices, practically all are now composed of metal 

 filaments (hence their name " metal filament lamps " 

 or " drawn wire lamps ") which, when rendered incan- 

 descent with the current, glow with a bright light in 

 their little glass globes from which the air has been 

 extracted. In the earliest of these lamps the filament 

 was made of carbon, and the connection with the 

 current was by means of thin platinum wires. These 

 early efforts were very feeble when compared with the 

 metal filament lamps of to-day. The metal now 

 employed in their construction is for the most part 

 tungsten, though this is by no means exclusively 

 the case. This metal, although it is by our definition 



a rarer metal, occurs in very large quantities through- 

 out the world as the mineral wolfram, which is found 

 among other places in our own Cornish tin-mines, 

 where it was a source of endless trouble to the early 

 miners, who threw it out on the dumps, not knowing 

 what to do with it. Since these early days tungsten 

 has become more valuable than the tin itself, not 

 only on account of its use in the electric bulb industry, 

 but also for the peculiar properties it confers upwn 

 steel, when it is alloyed with the latter, and it has 

 given rise to what is tantamount to a revolution in 

 this industry. Although tungsten was by no means 

 the first metal to be used in the steel industry for 

 this purpose, and is certainly not the only metal in 

 use to-day, it is perhaps of greater importance than 

 any other. On tungsten depends the resistance of 

 armour plate to enemy attack, and it is also invaluable 

 in the production of high speed tools, which do not 

 lose their temper even at a red heat. Tungsten has 

 on these two counts been called the key-metal of this 

 war by Colin G. Finck, who in a clever little article 

 has shown that the nation which could command 

 the supplies of tungsten was bound to gain the mastery, 

 as the Neolithic man armed with bronze was certain 

 to overcome his predecessor armed alone with stone, 

 and be overcome in turn by his successor with arms 

 or iron ; and so on throughout the ages, every victor 

 in turn gaining the mastery over his opponent by the 

 ascendancy conferred on him by some key-metal. 

 It seems hardly credible, under the circumstances, 

 that when the war broke out we were absolutely 

 dependent on Germany for our supplies of tungsten, 

 though the ores were actually exported from these 

 shores only to be returned to us as metal. This 

 state of things was very soon altered by the erection 

 of a Government tungsten factory at Widnes in 

 Lancashire, and Great Britain was rendered self- 

 supporting in this all-important metal. 



Most of the metals used for endowing steel with 

 special properties are prepared in the form of iron 

 alloys; among these maybe mentioned ferro-manganese, 

 ferro-tungstcn, ferro-chrome, and ferro-vanadium. As 

 a rule they are prepared by one of two methods, the 

 thermit process or the electrical furnace, in both of 

 which high temperatures are reached. The use made 

 of the rare metals is surprising to anyone not con- 

 versant with this matter. To take but one example : 

 vanadium is a rare metal, which some thirty years 

 ago was worth £90 per pound and was little more 

 than a chemical curiosity ; in ten years the price 

 fell to £3, and to-day a ferro-vanadium containing 

 30-35 per cent, vanadium can be bought for 30s. 

 the pound and considered dear at the price. The 

 reason for this changed state of affairs is the huge 

 demand created bv the wonderful vanadium steels. 



