CHEMISTRY OF INDUSTRIAL SUBSTANCES 157 



does not become decomposed, as do oils, by high tempera- 

 tures and the heat of friction. Since graphite is soft, it 

 readily wears away and when drawn across a piece of paper 

 the friction causes it to pulverize and leave a mark on the 

 paper. Hence its use in pencils. In addition, graphite 

 serves as the basic substance in the making of stove polish 

 and as an ingredient in the manufacture of certain crucibles 

 in which metals are to be heated and melted. 



Amorphous or non-crystalline carbon includes a number 

 of varieties of coal, charcoal, lampblack, coke, and gas 

 carbon. 



Charcoal is a black, brittle solid and is obtained by heat- 

 ing wood in a closed pile without much access to air. The 

 heat drives out the liquids and gases. These are collected 

 as a by-product and distilled into wood alcohol, acetic acid, 

 etc. Charcoal resists the action of moisture, heat, and air, 

 and consequently telegraph and other poles are often charred 

 before being put into the ground. It is also used as a disin- 

 fectant, because it absorbs gases. Gunpowder has a basis 

 of charcoal. The charring of bones and animal refuse gives 

 a form of charcoal called animal charcoal or bone-black, 

 which is used in making pigments. 



174. Oxides of Carbon. When any form of carbon or 

 carbonaceous matter burns, it forms a gas called carbon 

 dioxide. If there is insufficient air or oxygen and considera- 

 ble heat, a lower form of the oxide, called carbon monoxide, 

 is the result of the chemical change. Carbon dioxide has a 

 slight taste, but no odor and will not burn. Hence it is used 

 as a fire extinguisher. Carbon monoxide is a very poisonous 

 gas. It is a constituent of illuminating gas and burns with 

 a blue flame. 



