278 ECONOMIC GEOLOGY 



Now, the rupture of the best prepared steel is due to traces of the 

 oxides of Fe, even microlites of Fe 2 O 3 act like the stroke of a 

 diamond on the thickest glass. Vanadium steel acquires its 

 maximum hardness not by tempering, but by annealing at 700 

 to 800 C. A planing machine with vanadium steel cutting edges 

 can be set at work with the greatest velocity, and even when 

 heated at red-heat, it still continues to take off shavings of iron 

 or casting without exhibiting any signs of exhaustion. This 

 property is of vital importance in projectiles. The shock they 

 receive upon striking their mark raises them to a very high tem- 

 perature, yet vanadium steel retains all its sharpness, and its pene- 

 trating force remains intact. Ordinary steel softens and loses its 

 cutting power. Vanadium is destined to cause a revolution in 

 armaments. 



The salts of vanadium have considerable commercial signifi- 

 cance. F. L. Hess states that metavanadic acid is used as a 

 substitute for gold bronze in paint; that vanadium chloride is 

 used as a mordant in printing fabrics; that vanadium trioxide 

 is used as a mordant in dyeing; and that vanadium pentoxide is 

 used as a reducing agent in the treatment of organic compounds 

 in an acid bath. This anhydride is also used in the place of 

 platinum in the contact process for the manufacture of H 2 S0 4 , 

 and as a photographic developer. Vanadin is a medicinal prep- 

 aration with potassium chlorate. Vanadium salts are also used 

 as fertilizers, in coloring glass, and in the manufacture of a water- 

 proof black ink. 



Economics. The price paid for vanadic acid in 1910 was 

 about $2.50 per pound according to purity. The price paid for 

 the alloy ferro-vanadium was about $5 per pound of vanadium 

 content. 



UEANIUM 



Properties. Uranium, symbol U, is a rare and heavy metal. 

 Its melting point is 800 C; its specific gravity is 18.7, and its 

 atomic weight is 238.5 the highest of all known elements. 



Ores of the Metal. Uraninite, xU0 2 , yUOs, with some PbO, 

 and a little N. It crystallizes in isometric octahedrons, but usu- 

 ally occurs massive and granular. The color varies in shades of 

 gray, green and black. In uraninite, helium was first discovered 

 and later polonium. Both uranium and its compounds are 



