CARBON 



47 



Hessian crucible, and cover with sand. Heat the crucible until 

 smoking ceases (see Fig. 21). Remove and examine the charcoal. 



Questions. ( i ) What are the principal elements present in wood? 

 (2) What becomes of these various elements when the material is 

 heated? (3) Why was the sand used in this ex- 

 periment ? (4) What becomes of the ash or mineral 

 matter in the process of charcoal -making ? (5) 

 What is charcoal, and of what element is it prin- 

 cipally composed? (6) Does charcoal have a crys- 

 talline structure ? (7) What would be the result if 

 sand were not used in the experiment ? (8) Give 

 the equation for the combustion of carbon. (9) 

 How can charcoal be made on a large scale ? 



Particles of carbon can also be obtained from a 

 gas, candle, or lamp flame, by holding a piece of 

 cold porcelain a little above the flame. Carbon, in 

 the form of soot, is deposited in chimneys when 

 fuel is burned with a poor draft. When combus- 

 tion is complete, the carbon is oxidized, forming 



carbon dioxid. If a fire gives off a large amount Fig- 21. Prepara- 

 _ , tion of charcoal, 



of dense black smoke, the carbon is not com- 

 pletely oxidized, and consequently a loss of fuel value occurs. 



49. Properties. Carbon is found in three forms in na- 

 ture : as diamond, graphite, and amorphous carbon. 

 The diamond is a pure form of crystallized carbon. It is 

 capable of being burned the same as any other form of 

 the element, and produces carbon dioxid. Diamonds of 

 small size can be produced artificially by the cooling of 

 graphite from molten iron. Graphite is also a crystalline 

 form of carbon, but the crystals are of different shape and 

 color from diamonds. It is soft, and is used quite exten- 

 sively as a lubricant. As it does not burn as readily as other 

 forms of carbon, it is used frequently for making cruci- 



