228 ECONOMIC GEOLOGY 



from 83,000 to 91,000 Ib. per square inch. One alloy is said to 

 have a tensile strength of over 100,000 Ib. per square inch. 

 Aluminum bronze can be rolled into thin sheets, readily drawn 

 out into wire, spun, stamped, or pressed like ordinary brass. 

 It is extremely tough and malleable. Its smoothness enables 

 it to resist abrasion so that it is adapted for use as an anti- 

 friction metal. It resists corrosion far better than the bronzes 

 and tarnishes less readily upon exposure to moist atmosphere. 

 According to Sexton it can be kept at a red heat for months 

 without showing any signs of oxidation. The alloy is well 

 adapted for use in jewelry on account of its color, and for many 

 parts of machinery on account of its tensile strength, for propeller 

 blades for ships on account of its strength and non-corrosiveness, 

 and for the castings of heavy guns on account of its strength. 

 The strongest aluminum alloy known is said to consist of 27 per 

 cent, copper, 10 per cent, aluminum and 3 per cent, silicon. 

 Many alloys of aluminum containing 10 per cent, or less of copper 

 are widely used where lightness, strength and non-corrosiveness 

 are desired. Magnalium is an alloy of aluminum with mag- 

 nesium. It is lighter than pure aluminum with specific gravity 

 of 2.4. It is ductile and malleable. It can be spun, drawn or 

 forged like aluminum. It is non-corrodible and has a tensile 

 strength of 42,000 Ib. 



Ferro-aluminum is an alloy of aluminum and iron used largely 

 in the manufacture of steel. It is a yellowish white alloy, hard 

 and brittle. Aluminum unites with tin in the formation of a 

 series of useful alloys especially for optical instruments in the 

 place of brass. These alloys can be used in the place of aluminum 

 wherever lightness is desired. Aluminum and zinc form impor- 

 tant alloys. If a small amount of aluminum be added to zinc it 

 renders the metal more fluid. It therefore increases the area a 

 given amount of zinc will galvanize. It also reduces the amount 

 of oxidation that may occur. With 18 per cent, of zinc the alloy 

 is easily worked and of technical value. Aluminard is an alloy 

 of copper, nickel, zinc, and phosphorus. It takes a polish equal 

 to aluminum and is used in the castings for delicate machinery. 

 Partinium is a new alloy patented at Putaux, France. It is 

 designed for the bodies of steam omnibuses, bearings of engines 

 and shop shaftings. Aluminite is a fire-proof flooring used 

 extensively in kitchens, halls and grill rooms. It makes a light 

 soft flooring. 



