92 NON-METALS AND THEIR COMBINATIONS. 



13. CARBON. 



Civ = 12 (11.97). 



Occurrence in nature. Carbon is a constituent of all organic 

 matter. In a pure state it is found crystallized as diamond and 

 graphite, amorphous in a more or less pure condition in the various 

 kinds of coal, charcoal, boneblack, lampblack, etc. As carbon 

 dioxide, carbon is found in the air; as carbonic acid, in water; as 

 carbonates (marble, limestone, etc.), in the solid portion of our earth. 



Properties. The three different allotropic modifications of carbon 

 differ widely from each other in their physical properties. 



Diamond is the purest form of carbon, in which it is crystallized in 

 regular octahedrons, cubes, or in some figure geometrically connected 

 with these. Diamond is the hardest substance known ; it is infusible, 

 but burns when heated intensely, forming carbon dioxide. 



Graphite, plumbago, or black-lead, is carbon crystallized in short 

 six-sided prisms; it is a somewhat rare, dark -gray mineral, chiefly 

 used for lead- pencils. 



Amorphous carbon is a soft, black, solid substance. 



Neither form, of carbon is fusible, volatile, or soluble in any of the 

 common solvents. 



Carbon is a quadrivalent element ; it has little affinity for metals, 

 but combines with many of the non-metals, chiefly with oxygen, 

 hydrogen, and nitrogen, forming organic substances. 



Tests for carbon. 



1. Most non-volatile (organic) substances containing carbon, 

 blacken when heated on platinum foil. Starch or sugar may be used 

 for this test. 



2. The product of combustion of carbon (or of combustible matter 

 containing it), CO 2 , renders lime-water turbid, in consequence of the 

 formation of insoluble calcium carbonate, CaCO 3 . 



of atmospheric air be determined? 114. Mention some decompositions by 

 which ammonia is generated. 115. Explain the process of making water of 

 ammonia. 116. State the physical and chemical properties of ammonia gas 

 and ammonia water. 117. How is nitrogen monoxide obtained, and what are 

 its properties ? 118. Describe the process for making nitric acid, and give 

 symbols for decomposition. 119. How does nitric acid act on animal matter, 

 and what are its properties generally? 120. Give tests and antidote for nitric 

 acid. 



