280 APPENDIX. 



if the composition of the related compounds be expressed 

 in formulae, according to equivalents, the connection 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 shew, 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 O 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 

 eq. 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 



