A DREAM OF FAIR HYDRONE 485 



from methane upwards. Solid paraffin is a mixture of higher 

 terms of the series, the various constituents of petroleum — 

 petrol, burning oil, the mineral lubricating oils and vaselin — 

 consisting for the most part of intermediate terms. 



Methane is remarkable among hydrides as that in which 

 hydrogen is present in the highest atomic proportion in which 

 it is known to occur in any simple hydride, the typical hydrides 

 being as follows : 



As no compound of two elements is known in which a 

 single atom of hydrogen is associated with more than a single 

 atom of any other element, it is to be supposed that in all these 

 hydrides the several hydrogen atoms are separately attached 

 to the single atom upon which they attend. The valency or 

 atom-fixing power of hydrogen being taken as unity, that of 

 other elements which form hydrides is indicated by the number 

 of hydrogen atoms with which they severally unite. 



If it be granted that the hydrogen atom can be united 

 directly with but one other atom — in technical phraseology, 

 that hydrogen is always a monadic or univalent element — it 

 follows from the properties and composition of methane that a 

 single atom of carbon unites with and is satisfied by four atoms 

 of hydrogen ; in other words, it is tetradic or quadrivalent. 

 The molecule is practically saturated : that is to say, it has 

 little if any attractive power or tendency to unite with other 

 molecules ; moreover, what is true of a single carbon atom and 

 its associated hydrogen atoms is equally true of the more 

 complex systems of which the higher paraffins consist. 



And as the hydrogen atom cannot serve as the link between 

 other atoms, it necessarily follows that in the terms above 

 methane the carbon atoms are linked together among them- 

 selves and that only their spare affinities are to be regarded as 

 satisfied by hydrogen atoms. 



Thus the first homologue of methane — the term next to it in 

 the paraffin series — ethane, C 2 H 6 , is necessarily regarded as a 

 compound in which two tetrad atoms of carbon are united by 

 one affinity of each atom, leaving six affinities which are satisfied 

 by six hydrogen atoms or C 2 H = H 3 C ■ CH 3 . 



