Man's physical universe

xanabras

650 CREATIVE CHEMISTRY

The vaporizing-liquid type of extinguisher contains carbon tetrachloride,

which is forced onto the fire by a pump in the cylinder. Carbon

tetrachloride is a compound in which the carbon has been completely

oxidized by chlorine rather than by oxygen. Carbon tetrachloride

forms a heavy vapor that smothers certain types of fires such

as oil and gasoline fires quite efficiently if the vapors are confined over

the surface of the fuel.

Fig. 284. Note how the foam floats on the liquid shutting off the oxygen

and extinguishing the fire, and how the water goes to the bottom of the receptacle

allowing the burning liquid to overflow and the fire to spread. (Courtesy

of the American-La France and Foamite Industries,

Inc.)

Combustion Furnishes the Heat to Transform Many Inorganic Materials

into Useful Products.

1. Limestone Is Heated to Produce Lime. Any naturally occurring

carbonate, such as calcium carbonate (limestone, chalk, or marble)

or magnesium carbonate (magnesite), when heated to a high enough

temperature in large furnaces, or kilns, will decompose to form carbon

dioxide and the corresponding metallic oxides — lime, CaO, in the case

of limestone.

Lime, CaO, called quicklime, will react with water to form hydrated

lime, Ca(0H)2. This process, called "slaking," evolves considerable

heat. When lime is left exposed to the air, it combines with the carbon

dioxide to form calcium carbonate, CaCOa. This product is called

"air-slaked" lime.

Because of its low cost, hydrated lime (calcium hydroxide, Ca(0H)2)

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