

USEFUL METALS 



the manufacture of refractory lirick> in variou owing 1" 



its own refractoriness, will demand a larger u-e for chromite 

 than the known American depo.-its can supply. < 'hromite I, rick 

 are made of chromite and coal tar or some other binding mat 

 They are superior to magnesite brick in many particulars. 



Chromite is used as a mordant in producing shades of red, 

 green, buff, brown and black. Chromium is u>ed in the manufac- 

 ture of the red and yellow chromates for commercial trade and in 

 electrolysis. Some of the chromates are used directly as a pig- 

 ment. Chromium salts are used in printing, dyeing, and in wall 

 paper. Chromium is also used as an oxidizing agent and in tan- 

 neries. Chrome-tanned leather will resist the heating of high- 

 speed belts than any other leather known. It will stand a harder 

 usage. Chromium is also used in the manufacture of pottery. 

 Some chromium salts find a use in medicine. 



Chromium is used in the manufacture of steel. Here its spe- 

 cial value is its freedom from carbon, and by its use steels high 

 in chromium and low in carbon can be manufactured. Such 

 steels are extremely hard and tough, resist shocks and are of great 

 tensile strength. They are especially to be desired wherever 

 these properties play an important part. It is sometimes stated 

 that scales of chromium separate out and make such steel in- 

 capable of welding and that only an adhering union results. 

 However, the welded zone is equally as strong as the unbroken 

 steel. 



Chromium is used very largely in the manufacture of alloys. 

 The ferro-alloy is used with ferro-nickel in the manufacture of 

 chrome steel for armor plates, and armor-piercing projectiles, 

 trolley car wheels, crusher jaws, stamp mill shoes, so-called 

 burglar proof safes, tires, axles, springs, magnet steel, cutlery, 

 mechanical implements and bridge steel. 



The ferro-chrome alloy is produced under the intense heat of an 

 electric furnace from high-grade chrome ores low in silicon. The 

 iron, chromium, tungsten and nickel alloy is especially valuable 

 for high-speed tools on account of its resistance to heat and 

 abrasion. 



The value of chromite depends largely upon the percentage 

 of chromic oxide, Cr 2 Os present. The standard ore contains 

 50 per cent, of this oxide. It increases in value $ 1 per ton for every 

 unit above 50 per cent. It decreases in value for every unit less 

 than the standard 50 per cent. When the percentage of chromic 



