Ml-. J. Taylor's Ltxtures on Metallurgy. 289 



to compound one adapted to particular uses. In noticing the 

 principal alloys, it 16 to be observed, that gold and silver are 

 hardened, so as to be more useful than they would be in their 

 pure state, by the mixture of a little copper. 



Copper affords us man}' valuable alloys ; as with zinc, 

 brass; — with tin, gun-metal, bell-metal or bronze, and specu- 

 lum metal; — with tin and lead, pot-metal*. 



Tin alloyed with lead forms the common solder used by 

 plumbers : — and also with a proportion of antimony and a 

 small quantity of lead gives pewter. 



Lead and antimony form type metal, which has the I'equi- 

 site qualities of fusibility and considerable hardness. 



Shot is made of lead mixed with a small quantity of arsenic. 

 Iron is seldom alloyed with other metals : but steel has lately 

 been mixed with minute portions of silver, platina, rhodium, 

 &c. which are said to improve its qualit}'. 



Bismuth (8), lead (5), and tin (3), form an alloy so fusible 

 as to melt in boiling water; though no one of these metals se- 

 parately will melt under a temperature of 450°. 



Amalgams are combinations of mercury with other metals, 

 which in many instances readily take place even without the 

 assistance of heat; the mercury producing in this case a kind 

 of solution of the other metals. Use is made of this circum- 

 stance to separate gold and silver from the other substances 

 with which they are mixed in the earth. Amalgams are em- 

 ployed for many purposes. That of gold is used in gilding: 

 and silvering is performed in a similar manner in some in- 

 stances. The amalgam of tin is used in silvering (as it is 

 called) the backs of looking-glasses or mirrors. 



Another use made of the affinity ol" one metal for another, 

 is the coating applied to the surfaces by immersion. Thus 

 the coinmon tin plates which are so much in use, are made of 

 sheet iron dipped into melted tin, which with proper treat- 

 ment combines with a portion of the iron and adheres to it. 

 Copper for culinary vessels and many other purposes is tinned 

 in nearly a similar manner. 



Soldering is another instance of the use made of this affi- 

 nity. It is performed by applying a metal, or an alloy, more 

 fusible than the one the parts of which are to be united. The 

 solder is easily melted without disturbing the form of the 



• Standard Gold 38 grains of copper to 442 gold, making 480 =1 oz. 

 Silver 11 oz. 2dwts. silver in the pound, to 18 dwts. copper. 

 Gun metal 100 copper 8 to 12 tin 



Bell metal 70 20 to 10 zinc 



Speculum metal 60 30 to 10 do. and silver. 



Vol. 61. No. yOO. April 1823. O o metal 



