1 76 METALS USED IN THE HOME 



tive man's simple needs. As civilization advanced and man's 

 requirements increased, copper was put to more and more 

 various purposes. To-day not only are our kettles, heaters, and 

 boilers made of copper, but the trolley wires and our telephone 

 and telegraph wires are also of copper. The very books which 

 we read are printed from copper plates, and the materials which 

 we wear are designed from copper rolls. New metals have been 

 discovered and mined and used extensively, but none has re- 

 placed copper. 



A disadvantage of copper is that it is affected by moisture in 

 the air, and becomes covered with a green layer. Corroded 

 copper is similar in character to rusted iron, both processes be- 

 ing due to oxidation in a moist atmosphere. To prevent cor- 

 rosion, a protective covering is applied to the metal. 



Acids, such as fruit juices and vinegar, act readily upon 

 copper and form compounds which are injurious to the body. 

 For this reason copper cooking utensils are unsafe. Iron is 

 also acted upon by acids, but the compounds formed are not so 

 injurious to the body as the copper compounds. 



In addition to the free copper which is scattered abundantly 

 over the earth, there is considerable copper in ore. But not 

 until years after free copper was extensively used, did man learn 

 to extract metals from their ores. 



Tin. Tin is a silvery white metal. It is seldom found free, 

 and then only in small quantities. The ore from which it is 

 extracted is found in England, Australia, and India. Tin is 

 soft and malleable and can be beaten into thin sheets. These 

 tin sheets are called tin foil, and are used as a covering for 

 chocolate and other foods, and as a lining for candy, soap, and 

 cigar boxes. The so-called tin pan of the kitchen is not a real 

 tin pan ; if it were, it would be too soft for use. It is an iron 

 pan that has been dipped into melted tin, and has acquired a 

 tin coating (Fig. 63). The bright, shiny, clean appearance 



