HYDROCARBONS I 7 



with the tetrahedral formula for methane or for the carbon 

 atoms in organic compounds. This new isomerism is known 

 as space or stereo isomerism. 



Having thus developed, through a consideration of a few 

 compounds, some of the fundamental theoretical conceptions 

 of organic chemistry we shall now consider the compounds 

 themselves. 



The hydrocarbons are of importance to agriculture as con- 

 stituents of products which possess great value because of 

 extensive general use, such as gasoline, kerosene, lubricating 

 oils and greases, vaseline and paraffin, all of which are obtained 

 by the fractional distillation of petroleum. Also illuminating 

 gas obtained by distilling coal. They have an indirect value 

 also in the theoretical ways just explained, and in the fact that 

 they are products of the decomposition of plant and animal 

 bodies. An interesting fact is that the lower hydrocarbons, CH4, 

 methane, C2H6, ethane, CsHg, propane and C4H10, butane, are 

 gases, the next few liquids, and the higher members solids. 

 The solid members are contained in paraffin and, like it, are 

 wax-like substances. 



