the Paraffins and their Derivatives. 207 



iso-subclass, and by its meaning the intermediate nature of this 

 subclass, as associated witb tbat of the isoparaffins in being 

 formylic, and with tbat of the neoparaffins in being tetrame- 

 thylic. Taking tben the Greek letters <r, y, and p as indices of 

 tbe iso-, neo-, and meso-subclasses, tbe four best-known hexanes, 

 for instance, may be expressed by tbe following condensed 

 formulas respectively : — 



C 6 H U 6 H&. 6 H*. C fl H&.. 



Hexane. Isoliexane. Neokexane. Mesohexane. 



n f CH 2 .0Ho.CH o .0H 3 f CH 2 .CH 2 .CH 3 f CH 9 .CH 3 ^J CH 



- lCH 3 - " HC^CH 3 ■ CH; H ri0H 



I ^- 3 



oh; ■ tiG lcH 3 



LOH 3 H kjO] 



In tbe majority of cases, tbe grouped marsh-gas residues 

 CH 2 .CH 3 , CH 2 .CH 2 .CH 3 , CH 2 .CH 2 .CH 2 .CH 3 , and their homo- 

 logues, or ethyl, propyl, butyl, &c, are preferably represented 

 by the familiar condensed expressions C 2 H 5 , C 3 H 7 , C 4 H 9 , &c. ; 

 and employing these expressions, the several normal, iso- and 

 neoparaffins will appear as di-, tri-, and tetra-derivatives 

 respectively of methane or marsh-gas, and the several meso- 

 paraffins as tetra-derivatives of ethane, propane, and the suc- 

 ceeding homologues of marsh-gas, as exemplified in the fol- 

 lowing Table (p. 208); of formulas for the 3-, 4-, 5-, 6-, and 

 7-carbon paraffins. 



With regard to the setting out of the formulas of the normal 

 paraffins, it is to be observed that the formula given for pen- 



tane, for instance, H 2 C^ p 3 Tx 7 or propyl-methyl methane, is 



only one condensed form of the expression 



H 3 C.H 2 C.H 2 C.H 2 C.CH 3 , 



and that, so far as the nature of the paraffin is concerned, other 

 condensed forms of the expression, as H 3 C.C 4 H 9 or butyl- 



methane, H 5 C 2 .C 3 H 7 or propyl-ethane, H 2 C«J p 2 -™- 5 or di- 



f PIT 



ethyl-methane, and H 6 C 3 S qjj 3 or dimethyl-propane, are just 



as correct, and are each of them, in view of certain reactions 

 and relations, even more convenient. But upon the whole, the 

 mode of setting out the formulas of the normal paraffins made 

 use of in the Table appears to be most generally advantageous, 

 from its best illustrating the relationship of the normal to the 

 iso- and neoparaffins, and more particularly, as will hereafter 

 be seen, from its best illustrating the relationship of the normal 

 paraffins both to their derived ketones and secondary alcohols, 

 and also to their associated olefins. This mode of expression, 



