the reduction of Oxides of Silicon, Aluminum, etc. 311 



the aluminum contained, the lowest market quotation of this 

 metal being at present $15 per pound. Silicon bronze can be 

 furnished at prices far below those of the French manufacturers. 



The alloys, which the metals obtained by the methods above 

 described form with copper, have been submitted to careful 

 study. An alloy containing 10 per cent of aluminum and 90 per 

 cent of copper forms the so-called aluminum bronze, with a fine 

 golden color, that is retained in the atmosphere for a long time. 

 The tensile strength of this alloy is usually given as 100,000 

 pounds to the square inch ; but castings of our 10 per cent bronze 

 have stood a strain of 109,000 pounds. It is a very hard, tough 

 alloy, with a capacity to withstand wear far in excess of any 

 other metal in use. All grades of aluminum bronze make fine 

 castings, taking very exact impressions, and there is no loss in 

 remelting as in the case of alloys containing zinc. The 5 per 

 cent aluminum alloy is a close approximation in color to 18 

 carat gold and does not tarnish readily. Its tensile strength in 

 the form of castings is equivalent to a strain of 68,000 pounds 

 to the square inch. An alloy containing 2 or 3 per cent alumi- 

 num is stronger than brass, possesses greater permanency of 

 color and would make an excellent substitute for that metal. 

 When the percentage of aluminum reaches 13 an exceedingly 

 hard, brittle alloy of a reddish color is obtained; and higher 

 percentages increase the brittleness and the color becomes 

 grayish-black. Above 25 per cent the strength again increases. 



The effect of silicon in small proportions upon copper is to 

 greatly increase its tensile strength. When more than 5 per 

 cent is present the product is exceedingly brittle and grayish- 

 black in color. It is probable that silicon acts to a certain ex- 

 tent as a fluxing material upon the oxides present in the copper, 

 thereby making the metal more homogeneous. On account of 

 its superior strength and high conductivity for electrical cur- 

 rents, silicon bronze is the best material known for telegraph 

 and telephone wire. 



The element boron seems to have almost as marked an effect 

 upon copper as carbon does upon iron. A small percentage in 

 copper increases its strength to 50,000 or 60,000 pounds per 

 square inch without diminishing to any extent its electrical 

 conductivity. 



Aluminum increases very considerably the strength of all 

 metals with which it is alloyed. An alloy of copper and 

 nickel with a small percentage of aluminum, called Hercu- 

 les metal, withstood a strain of 105,000 pounds and broke 

 without elongation. Another grade of this metal broke under 

 a strain of 111,000 pounds with an elongation equivalent to 

 33 per cent. It must be remembered that these tests were all 

 made upon castings of the alloys. The strength of common 

 brass is doubled by the addition of 2 or 3 per cent of alumi- 



