96 ALLOY 



Another of his alloys is composed of 66 Ibs. of foreign zinc, 33.} tin, 3^ antimony; 

 or 70 J zinc, 19J tin, and 2 antimony ; or any intermediate proportions, and with or 

 without arsenic. He uses black flux. When to bo applied to tho sheathing of ships, 

 from 8 to 16 oz. of metallic arsenic are added to every 100 Ibs. of alloy. A third class 

 of alloys consists of equal parts of iron and nickel ; the copper is next added, and 

 lastly tho zinc, or tho copper and zinc may bo added as an alloy. 100 Ibs. may con- 

 sist of 45.} Ibs. of iron and nickel (paries aquales), and 10 Ibs. of foreign zinc; or 

 30 J Ibs. of alloy of iron and nickel (p. <e.) t 46 copper, and 26 zinc ; or any interme- 

 diate proportions of zinc and copper. Ho uses also an alloy of 60 Ibs. of copper, 20 

 of zinc, and 20 of silver ; or 60 copper, 10 nickel, 10 silver, and 20 zinc ; tho copper 

 and nickel being first fused together. His fifth alloy is called by him a non-conductor 

 of heat ! It is made of 25 nickel, 25 iron, and 50 copper ; or 15 nickel, 25 iron, and 

 60 copper ; the last being added after the fusion of tho others. 



It may prove convenient to give a general statement of the more striking pecu- 

 liarities of tho important alloys. More detailed information will be found under the 

 heads of tho respective metals. 



GOLD AND SILVER ALLOYS. The British standard for gold coin is 22 parts pure 

 gold and 2 parts alloy, and for silver, 222 parts pure silver to 18 parts of alloy. 



The alloy for tho gold is an indefinite proportion of silver and copper : somo coin 

 lias a dark rod colour from the alloy being chiefly copper ; the lighter the colour a 

 larger portion of silver is indicated, sometimes even (when no copper is present) it 

 approaches to a greenish tingo, but the proportion of pure gold is the same in either 

 case. 



Tho alloy for silver coinage is always copper ; and a very pure quality of this 

 metal is used for alloying, both for the gold and silver coinage, as almost any other 

 metal being present, even in very small quantities, would make the motals unfit 

 for coinage, from rendering the gold, silver, and copper brittle, or uot sufficiently 

 malleable. 



The standard for plate (silver) is the same as the coin, and requires the same 

 quantity of copper, and carefully melting with two or three bits of charcoal on the 

 surface while in fusion, to prevent the oxidation of the copper by heat and exposure 

 to the atmosphere. 



The gold standard for plate and jewellery varies, by an Act of Parliament, 

 from the 22 carats pure, to 18, 12, and 9 : the alloys are gold and silver, in various 

 proportions according to the taste of the workmen ; the colour of the articles manu- 

 factured depending, as with the coin, on the proportions ; if no copper is used in 

 qualities under 22 carats fine gold, the colour varies from a soft green to a greenish 

 white, but a proportion of copper may be used so as to bring the colour to nearly that 

 of 22 fine, 1 silver, and 1 copper. 



Wire of either gold or silver may be drawn of any quality, but tho ordinary wire 

 for fine purposes, such as lace, contains from 5 to 9 pennyweights of copper in 

 the pound of 240 pennyweights, to render it not so soft aa it would be with pure 

 silver. 



Gold, silver, and copper may be mixed in any proportions without injury to the 

 ductility, but no reliable scale of tenacity appears to have been constructed, although 

 gold and silver in almost any proportions may be drawn to the very finest wire. 



The alloys of silver and palladium may be made in any proportions ; it has been 

 found that even 3 per cent, of palladium prevents silver tarnishing so soon as without 

 it ; 10 per cent, very considerably protects the silver, and 30 per cent, of palladium 

 will prevent the silver being affected by fumes of sulphuretted hydrogen unless very 

 long exposed : the latter alloy has been found useful for dental purposes, and the 

 alloy with less proportions say 10 to 15 per cent. has been used for graduated 

 scales of mathematical instruments. 



The alloy of platinum and silver is made for the same purposes as those of palla- 

 dium, and, by proper care in fusion, are nearly equally useful, but the platinum does 

 not seem to so perfectly combine with the silver as the palladium. Any proportion 

 of palladium with gold injures the colour, and even 1 per cent, may be detected by 

 sight, and 5 per cent, renders it a silver colour, while about 10 per cent, destroys it; 

 but the ductility of the alloy is not much injured. 



Gold leaf for gilding contains from 3 to 12 grains of alloy to the ounce. Tho gold 

 used by respectable dentists is nearly pure, but necessarily contains about 6 grains of 

 copper to the ounce troy, or ^th part. 



Antimony in the proportion of ^^ quite destroys the ductility of gold. 



Gold and platinum alloy forms a somewhat elastic metal. Hermstadt's imitation 

 of gold consists of 16 parts of platinum, 7 parts of copper, and 1 of zinc, put in a 

 crucible, covered with charcoal powder, and molted into a mass. P. J. 



