188 OUTLINE OF CHEMICAL STUDY 



216. Ores. Most of the metals are found in the 

 earth in the form of ores. An ore is a mineral substance 

 containing a metal that may be removed from it for 

 man's use. The mineral substance may be any sort of 

 rock mass. The metal itself is mixed with the rock, 

 sometimes in its free (or uncombined) state, but more 

 often as an oxide, a sulphide, or a salt. That is, if 

 we were to see an ore of some metal, we should see 

 a rock in which were scattered masses of possibly 

 the pure metal itself, but more likely of some salt, 

 oxide, or sulphide of the metal. Iron, copper, tin, lead, 

 silver, gold, zinc, and a few other metals are taken 

 from ores. 



217. Alloys. An alloy is a mixture of two or more 

 metals, made by melting them together. Many alloys 

 may at first thought seem to be metals ; they are not 

 elements, however, but are made by man's work. Brass 

 is an alloy of copper and zinc ; bronze is made of tin 

 and copper ; solder contains tin and lead ; gun metal 

 and bell metal contain copper and tin in different pro- 

 portions. G-erman silver is an alloy of copper, zinc, and 

 nickel; type metal contains lead and antimony; and pew- 

 ter is an alloy of lead and tin. 



218. Hydrocarbons. An hydrocarbon is a compound of 

 hydrogen and carbon. There are many hydrocarbons, for 

 these elements unite in various ratios. Two common hydro- 

 carbons may serve as examples : acetylene (C 2 H 2 ), a com- 

 mon illuminant used in automobile headlights ; and marsh 

 gas (CH 4 ), the explosive " fire damp " of coal mines. Kero- 

 sene and other petroleum products contain hydrocarbons. 



