516 report — 1878. 



TUESDAY, AUGUS1 20, 1878. 

 The following Papers were read : — 

 1. On a Simplification of Graphic Formula;. By Oliver J. Lodge, D.Sc. 



In the graphic formulae of a compound the elements are ordinarily represented 

 by their chemical symbols (capital letters), and the connection between the atoms 

 by straight lines joining the letters. Now graphic formulae are of most use in 

 organic chemistry, where the principal compounds consist only of the elements 

 C, H, 0, and N, whose atomicities are generally 4, 1, 2, and 3 or 5 respectively. In 

 any formulas, therefore, four bonds generally radiate from the letter ; N is the 

 meeting-place of three or five bonds, according to ■ circumstances ; two bonds meet 

 at each 0, and a single bond terminates at every H. Supposing then that the 

 letters were omitted and the bonds joined together, the position of the atoms would 

 still be apparent as the meeting-place of a definite number of bonds, and therefore 

 the letters are unnecessary. 



The simplification proposed in the paper is the omission of the usual symbols 

 used to denote the atoms, and the joining of the bonds in such a way as clearly to 

 define the atomicities, and therefore the natures of the several atoms. Formulae 

 so drawn become reduced to a sort of geometrical diagram ; and conversely any 

 geometrical diagram represents some real or imaginary chemical compound. 



For instance, in the accompanying figure — 



12 3 4 5 



+ -H- J- % 



6 7 8 9 



$ f * ** h 



(1) represents CH 4 or marsh gas. (2) is common alcohol. 



(3) is acetic acid. (4) propionic acid. 



(5) Succinic acid (without the 2 bars in the middle it would be oxalic, with 

 only one malonic, acid), and so on. 



The free bonds of unsatisfied radicals are easily indicated by arrowheads. 



When chlorine or iodine substitution compounds are to be shown, the free ends 

 may be dotted, to indicate that the monad is not hydrogen, e.g., Secondary propyl 

 iodide, No. (6). In all cases where graphic formulae are used, the common em- 

 pirical formulae will or should be written alongside ; and the element intended by 

 the dot in any particular case will therefore be clear. Other details and numerous 

 illustrations are given in the paper. The constitution of a body is thus exhibited in 

 a very compact form which appeals to the eye and impresses itself readily on the 

 memory. The formulae of even complex bodies are very rapidly drawn, for a few 

 strokes, instead of representing but a single atom, as H, represents a whole group ; 

 for instance (7) is the radical ethyl ; (8) is prussic acid ; (9) amnionic cyanide ; (10) 

 is urea ; and the commonly occurring radicals are recognised at once without taking 

 the formulae to pieces. At the same time the symbols denoting the different radicals 

 are such as arise naturally, and are not arbitrary and intrinsically meaningless such 

 as even Et must be held to be ; and they may always be analysed whenever required. 



