

USEFUL METALS 185 



wall, Midland, the ore is mined, hoisted to the surface (for some 

 of these mines an- Ix'iug operated at a depth of over 1,300 ft.), 

 Iran-ported to t lie stamp mill when- it is broken down by hanuii' r- 

 wielde.l hy women, crushed in the stamp mill sufficiently fine 

 to pass through a 40-mesh sieve, carried by water to the dressing 

 floor where it is concentrated into black tin consisting of about 

 lili per cent. tin. This concentrated product is either >old direct 

 as tin ore or is mixed with 20 per cent, pulverized charcoal and 

 smelted. 



Uses of Tin. A large amount of tin is used in the manufacture 

 of the tinware of commerce. The object to be plated is dipped in 

 a bath of molten tin. The interior of the tin is a sheet of iron of 

 varying thickness. The exterior of the tinware is a thin coat or 

 film of tin. Between the two there is a thin band of alloy of tin 

 and iron which serves to unite the two metals. When the surface 

 of the iron is not perfectly smooth protuberances will perforate 

 the tin and in a short time, through the oxidation of the iron, the 

 dish will leak. 



Tin is used extensively in the manufacture of alloys. Tin 

 enters into combination with a large number of useful metals 

 forming alloys of commercial significance. With lead, tin will 

 mix in all proportions. The alloys are white and melt at a tem- 

 perature below the melting-point of tin. One of the most im- 

 portant of these is known as solder which consists of varying 

 proportions of tin and lead. Common solder consists of 1 part 

 of tin and one of lead. Coarse solder of 1 part of tin and two 

 of lead. Fine solder consists of 2 parts of tin and one of lead. 



The old pewter ware which has become so highly prized for 

 decorative effect in many dining rooms consists of 3 parts 

 of tin and one of lead. The old britannia ware consists of 84 

 parts of tin, 10 parts of antimony, 4 parts of copper, and 2 parts of 

 bismuth. Bell metal consists of 20 parts of tin and 80 parts of 

 copper. 



Tin is a constituent of a few brasses of importance, but, strictly 

 speaking, brass is an alloy of copper and zinc. Tin is a necessary 

 constituent of all bronzes. Many of these are capable of wide in- 

 dustrial application. It is also a requisite constituent in speculum 

 metal. It is used in the manufacture of naval condensers. It 

 is found also in many forms of babbitt. The true babbitts 

 carry more then 50 per cent, of tin. They are known as friction- 

 bearing alloys. 



