8 REPORT — 1859. 



or more distinct kinds, we must give to it a formula derived from the com- 

 bination of the types corresponding to the decompositions in question ; that 

 is to say, the more numerous are the reactions which we take into account it) 

 constructing the rational formula of any substance, the more complex must 

 be the type from which that formula is derived. Secondly, it is obvious that 

 complication of type involves simplification of radicles ; for in any com- 

 pound, the greater the number of atoms which are regarded as belonging to 

 the type, the smaller the number left to constitute the radicle. 



We see therefore that rational formulae of the highest possible degree of 

 generality would contain radicles of the greatest possible degree of simplicity ; 

 that is, consisting of single atoms of the elementary bodies. And in the case 

 of every compound of which our knowledge is extensive enough for us to be 

 able to trace, through a series of reactions which affect it more and more 

 deeply, the successive separation of all its atoms, one from another, or the 

 process of the recombination of these atoms into the original compound, the 

 rational formula, which would express the sum of our knowledge respecting 

 it, would actually take the form we have mentioned. 



In illustration of these remarks, we may consider briefly the known reac- 

 tions of acetic acid, and the way in which they may be expressed by rational 

 formute. 



1. The relation of acetic acid to the acetates shows that it contains an 

 atom of hydrogen which can be separated from the other atoms. The rational 

 formula expressing this is 



C 2 H 3 O 2 . H. 



2. In the decomposition of acetic acid by pentachloride of phosphorus, 

 and by pentasulphide of phosphorus, as well as in its conversion into aceta- 

 mide, one half of its oxygen is separated from it. Considering this result in 

 connexion with the formula deduced in (1), we obtain the formula 



C 2 H 3 O.H.O, or C2 JJ 3 °0; 



which expresses that an atom of hydrogen, or an atom of oxygen, or both 

 together, may be separated from acetic acid, while the rest of its atoms remain 

 combined. 



3. Acediamine, C 2 H G N 2 *, acetonitrile, C 2 H 3 N, and the substance 

 C 2 H 3 C1 3 (formerly terchloride of acetyl, but now without a name), are 

 derivatives of acetic acid in which it is represented by the triatomic radicle 

 C 2 H 3 . Hence the last formula must be replaced by 



(C 2 H 3 )'"0 . . , , ... H 2 01 

 v HO' derived from the type h 2 O l ' 



4. There are many reactions in which a compound belonging to the car- 

 bonic group and one belonging to the methylic group are formed simul- 

 taneously from acetic acid or one of its derivatives, or in which an acetic 

 compound is formed synthetically from a compound of the carbonic group 

 and one of the methylic group. We may mention — 



(A) of decompositions, the formation of a carbonate and acetone by 

 the distillation of an alkaline acetate by itself, or of a carbonate and 

 marsh-gas when it is distilled with an alkaline hydrate ; the electrolytic 

 decomposition of acetic acid ; the formation of kakodyle ; the produc- 

 tion of disulphometholic acid and carbonic anhydride by the action of 

 fuming sulphuric acid on acetonitrilef ; the decomposition of glycocol 



* Strecker, Ann. Chem. Pharm. ciii. 328. 



t Buckton and Hofmann, Chem. Soc. Quart. Journ. ix. 243 j Ann. Chem. Pharm. c. 133. 



