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XXV. On the Formulation of the Paraffins and their Deriva- 

 tives. By William Odling, M.B., F.R.S.* 



A SERIES of hydrocarbons, of composition and unit- 

 weight expressible by the formulae CH 4 , C 2 H 6 , C 3 H 8 , 

 C 4 H 10 , C 5 H 12 , &c. respectively, constitutes the series of the 

 paraffins (H. Watts). The first member of the series, CH 4 or 

 H 4 C, is familiarly known as marsh-gas; and the series itself 

 is sometimes spoken of as the marsh-gas series. 



Each successive member of the series differs in composition 

 from the immediately preceding member by an increment of 

 carbo-hydrogen, CH 2 ; and as, in the unit-weight of every 

 member of the series, the number of proportions of hydro- 

 gen exceeds by two proportions twice the number of pro- 

 portions of carbon, the series itself, as well as each member of 

 it, is expressible by the general formula G n H 2 „ +2 . 



Excluding the earlier terms, the members of the paraffin 

 series are noteworthy for the number of their isomeric modifi- 

 cations. Thus there are two known paraffins expressible by 

 the formula C 4 H 10 , three by the formula C 5 H 12 , four or five by 

 the formula C 6 H 12 or H 12 C 6 , &c. 



The paraffins are met with principally as products of destruc- 

 tive distillation, but are obtainable also by various definite 

 reactions. And, in particular, a large number of them have 

 been produced, directly or indirectly, by the coalescence of two 

 or more marsh-gas residues, as set forth below. 



From a study of the modes of formation and transformation 

 of certain members of the paraffin series, it results that every 

 paraffin may be regarded as producible by the coalescence of 

 two or more marsh-gas residues, in such a way that each par- 

 ticular residue coalesces with as many other residues as it is 

 itself deficient in the full number of proportions of hydrogen 

 proper to marsh-gas, H 4 C or CH 4 . 



Thus, of the four residues, methyl, H 3 C or CH 3 , methylene, 

 H 3 C or CH 2 , formyl, HC or CH, and carbon, C, the residue 

 methyl coalesces with one other residue only, whether tri-, di-, 

 mono-, or anhydric ; while the residue methylene coalesces 

 with two, the residue formyl with three, and the residue carbon 

 with four other residues, whether alike or different, and whether 

 anhydric, monohydric, or polyhydric respectively. 



The notion of these various ways of coalescence is expressed 

 in the following fully developed formulae for some of the pa- 

 raffins, — coalescence of the different residues being implied by 

 the lateral contiguity of their respective symbols : — 



* Communicated by the Author. 



