300 CONSIDERATION OF CARBON COMPOUNDS 



a gas at the ordinary temperature ; if it contains from 4 to 10 or 12 

 atoms of carbon, it is a liquid ; and if it contains a yet higher number 

 of carbon atoms, it is generally a solid. 



All hydrocarbons may be volatilized without decomposition, all 

 are colorless substances, and many have a peculiar and often charac- 

 teristic odor ; they are generally insoluble in water but soluble in 

 alcohol, ether, disulphide of carbon, etc. 



In regard to chemical properties, it may be said that hydrocarbons 

 are neutral substances, behaving rather indifferently toward most 

 other chemical agents. Most of them are, however, oxidized by the 

 oxygen of the air, by which process liquid hydrocarbons are often 

 converted into solids. 



Hydrocarbons of the paraffin or methane series. The hydro- 

 carbons having the general composition C n H 2n + 2 are known as 

 paraffins, the name being derived from the higher members of the 

 series which form the paraffin of commerce. The following table 

 gives the composition, boiling-points, etc., of the first sixteen mem- 

 bers of this series : 



B. P. Sp. gr. 



Methyl hydride or methane, C H 4 \ 



Ethyl hydride or ethane, C 2 H 6 I gases. 



Propyl hydride or propane, C 3 H 8 J 



Butyl hydride or butane, C 4 H 10 1 C. 



Amyl hydride or pentane, C 5 H 12 38 0.628 



Hexyl hydride or hexane, C 6 H u 70 0.669 



Heptyl hydride or heptane, C 7 H 16 99 0.690 



Octyl hydride or octane, C 8 H 18 125 0.726 



Nonyl hydride or nonane, C 9 H 20 148 0.741 



Decyl hydride or decane, C 10 H 22 166 0.757 



Undecyl hydride or undecane, C n H 24 184 0.766 



Dodecyl hydride or dodecane, C 12 H 26 202 0.778 



Tridecyl hydride or tridecane, C 13 H 28 218 0.796 



Tetradecyl hydride or tetradecane, C U H 30 236 0.809 



Pentadecyl hydride or pentadecane, C lg H 32 258 0.825 



Hexadecyl hydride or hexadecane, C 16 H 34 280 

 etc. 



The above table shows that the paraffins form an homologous 

 series ; the first four members are gases, most of the others liquids, 

 regularly increasing in specific gravity, boiling-point, viscidity, and 

 vapor density, as their molecular weight becomes greater. 



The paraffins are saturated hydrocarbons, the constitution of which 

 has been already explained; they are incapable of uniting directly 

 with monatomic elements or residues, but they easily yield sub- 



