54 



Biological Chemistry. 



The following is a list of some of the chief members 

 of the series : 



CH 4 



an 



614 



C 7 H 



^10^22 



+ 4 

 -45 

 



+ 37 

 69 

 98 

 125-5 

 149-5 

 173 



under 180 atmospheres. 

 46 



under ordinary atmospheric 

 pressure (760 mm.). 



Methane, 



Ethane, 



Propane, 



Butane, 



Pentane, 



Hexane, 



Heptane, 



Octane, 



Nonane, 



Decane, 



The above numbers refer to the " normal " or " straight- 

 chained " compounds. 



The Preparation and Properties of the Paraffin 

 Hydrocarbons. It has already been stated that it is very 

 difficult to isolate paraffin hydrocarbons in a pure con- 

 dition from the complex mixture in which they are found 

 native. They can, however, be readily prepared from the 

 sodium salts of certain acids which are obtainable in a 

 pure condition, either by synthesis or from natural sources, 

 when these substances are distilled with soda-lime. The 

 acids in question are known as the " fatty acids," and 

 possess the general formula C^H^Og. As an example of 

 this reaction, the preparation of methane from sodium 

 acetate, the sodium salt of acetic acid, may be cited 

 C 2 H 3 2 Na + NaOH = CH 4 + Na 2 C0 8 



In general, a hydrocarbon of the formula C n H 2n+2 may 

 be obtained from acids of the 

 which the sodium salt has the formula C 

 They can also be obtained synthetically by the treatment 

 of the halogen derivatives with sodium or zinc. This 

 synthetical method, which is of great historical impor- 

 tance, is due to Wiirtz. It may be illustrated by the 



formula C n+1 H 2n+2 O 2 , of 

 7i-fiH 2n+ iO 2 Na. 



