398 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



which Lavoisier had felt for postulating the existence of 

 " matter of fire " and " matter of heat " as imponderable 

 constituents of substances, set free from them when they 

 combined together. In this attempt at unification Berzelius 

 anticipated, not only the science of Thermo-chemistry, which 

 attempts to measure the energy of chemical combination in 

 units of heat, but also the later and more accurate method 

 of expressing energy of combination in terms of electro-motive 

 forces. 



C. THE THEORY OF COMPOUND RADICALS. 



Structure of organic compounds. Presence of compound 

 radicals. Berzelius's dualistic electro-chemical theory was 

 based upon his observations of the decomposition of mineral 

 substances by the electric current, and was applied primarily 

 to salts, acids and bases, which yielded readily to this treat- 

 ment. But it threw very little light upon the structure of 

 organic substances, such as sugar, alcohol, or olive-oil, which 

 would not conduct the current and were not decomposed 

 by it. Lavoisier, who regarded the mineral acids as binary 

 compounds of oxygen with a simple elementary radical such 

 as carbon, sulphur or phosphorus, had been obliged to 

 recognise that the organic acids contained oxygen in combin- 

 ation with both carbon and hydrogen, and sometimes also 

 with nitrogen and phosphorus ( Works, I. 147). These com- 

 pound radicals could not be resolved by the dualistic theory 

 and were frankly recognised by Berzelius as demanding 

 exceptional treatment. 



" [Compounds] of the first order are composed of simple 

 elementary atoms ; they are of two kinds, organic and 

 inorganic. /The latter never contain more than two 

 atoms; the latter always contains at least three" {Chemical 

 Proportions, 1819, p. 26). 



" In inorganic nature all oxidised bodies contain a simple 

 radical, while all organic substances are oxides of compound 



