266 CHEMICAL DISCOVERY AND INVENTION 



scratch glass, it is somewhat similar to iron when polished but 

 is not magnetic and is unaltered by moist air. It combines with 

 carbon in several proportions, forming the carbide Cr 4 C and at 

 the higher temperature of the electric furnace the compound 

 Cr 3 C 2 (Moissan). Its hardening effect on steel appears to be 

 closely connected with the amount of carbon present. It is now 

 used in fairly large quantity for the manufacture of steel tires, 

 springs, and axles, and for armour plate. 



Tungsten is a very infusible metal found in the form of the 

 mineral wolfram which is a tungstate containing the oxide W0 3 . 

 This compound can be reduced to the metallic state by heating 

 with coke in the presence of cast-iron. The product is known as 

 ferro-tungsten, and is used as an alloy in steel for the production 

 of so-called " self-hardening " steels. It is associated with 

 manganese in the well-known Mushet steel, and is sometimes 

 introduced together with chromium in steel required for machine 

 tools working at high speed. Molybdenum which is very similar 

 to tungsten has also been used. 



Vanadium and tantalum are other elements which have been 

 tried as ingredients in steel. Vanadium has a curious history, 

 for the substance which during forty years had passed as the 

 metal itself was shown by Roscoe to be a compound of that sub- 

 stance with nitrogen. Vanadium though not rare is far from 

 abundant, and the cost will necessarily have the effect of limiting 

 its application in steel-making to special purposes. Fortunately 

 the addition of very small quantities of vanadium is sufficient to 

 modify the properties of steel substantially. The addition of 

 0-6 per cent of vanadium to a pure iron and carbon steel (con- 

 taining 1-1 per cent of carbon) raised its tensile strength from 

 about 30 tons to 85 tons per square inch. There is need for 

 much further research in this direction. 



Titaniferous iron ores exist in immense quantities in Sweden 

 and in the form of sands in the United States, Canada, and New 

 Zealand. In the blast furnace only a portion of the titanic 

 oxide, Ti0 2 , is reduced and passes into the iron. There has been 

 difficulty in introducing titanium into steel, but the presence of 

 a small quantity is said to assist in the production of a sound 

 ingot. It has a tendency to combine with nitrogen and may in 

 this way prevent the formation of blowholes. 



