268 APPENDIX. 



nexion in each case becomes obvious, even to him who 

 knows no more of chemistry than that C represents an 

 equivalent or combining proportion of carbon, H an 

 equivalent of hydrogen, and O an equivalent of oxygen. 



Formula Formula 



of acetic acid. of aldehyde. of benzoic acid. of oil of bitter almonds. 



C 4 H 4 4 C 4 H 4 2 C 14 H 6 4 C 14 H 6 2 . 



These formulae are exact expressions of the results of 

 analysis, which, in each of the two cases quoted, refer to 

 a fixed quantity of carbon ; in one to 4 equivalents, in the 

 other to 14. They show, that acetic acid differs from 

 aldehyde, and benzoic acid from oil of bitter almonds, 

 only in the proportion of oxygen. 



Nor is it more difficult to understand the signification 

 of the following formulae. 



Cyamelide. 1 eq. cyanuric acid. 3 eq. hydrated cyanic acid. 



C 6 N 3 H 3 6 = Cy 3 ( = C 6 N 3 )0 3 + 3HO = 3(CyO + HO) = 

 =C 6 N 3 H 3 6 =C 6 N 3 H 3 6 . 



(In these formulae, N represents an equivalent of nitro- 

 gen, and Cy an equivalent of cyanogen. This latter sub- 

 stance being composed of 2 equivalents of carbon and 1 

 equivalent of nitrogen, Cy = C 2 N.) 



The first formula (that of cyamelide) is what is called 

 an empirical formula, in which the relative proportions of 

 the elements are, indeed, exactly known, but where we 

 have not even a theory, far less any actual knowledge, of 

 the order in which they are arranged. The second for- 

 mula is intended to express the opinion, that 3 eq. of 

 cyanogen (=6 eq. of carbon -(-3 eq. of nitrogen) having 

 united to form a compound atom or molecule, have com- 

 bined with 3 eq. of oxygen and 3 eq. of water, to form 





