4 86 SCIENCE PROGRESS 



The composition of the higher terms is expressed similarly 

 on paper, decane, for example, by the formula : 



HHHHHHHHHH 



I I I I I I I I I I 

 H— C— C— C— C— C— C— C— C— C— C— H 



I I I I I I I I I I 

 HHHHHHHHHH 



Such hydrocarbons, it will be obvious, consist of a succession of 

 terms each of the value CH 2 and of two end terms each of which 

 contains an additional atom of hydrogen : hence the expression 

 of their composition by the formula CnH^ + o. 



These conclusions as to the constitution of paraffin hydro- 

 carbons, based on the simple assumptions that hydrogen is a 

 monadic and carbon a tetradic element, have been completely 

 verified in practice. For example, if methylic alcohol, CH 3 (OH), 

 be converted by the action of hydrogen iodide into methylic 

 iodide and this latter be subjected to the action of a metal, the 

 iodine is withdrawn and the hydrocarbon residue or radicle 

 CH 3 at once unites with a second such group of atoms formed 

 from another molecule of the iodide : 



CHJ - I = CH, ; CH 3 + CH, = H,C " CH, 



The process is precisely similar to that by which hydrogen 

 gas is formed from hydrogen iodide : 



HI - I = H ; H + H = H, 



If the iodide prepared from ethylic alcohol, C 2 H 5 (OH), be used, 

 diethyl or tetrane is produced : 



CH, . CHJ + CH S . CH,I + 2 Na = 2 Nal + CH, . CH 2 . CH 2 . CH, 



Or if a mixture of two iodides be submitted to the action of the 

 metal, the respective hydrocarbon radicles become united ; thus : 



CHJ + CH 3 . CHJ + 2 Na = CH, . CH 3 . CH, + 2NaI 



Hydrocarbons of any degree of complexity may be built up in 

 this manner. 



The operation is akin to that of forming a simple chain by 

 forging link upon link ; on this account, such conjunctions of 

 simple hydrocarbon radicles are spoken of as open chain hydro- 

 carbons. Apparently there is no limit to the length of such 

 open chains. 



But closed chains or rings of carbon atoms may be formed by 



