8 CHEMICAL CONSTITUTION [iNTROD. 



by a very high number. Respecting the mode of combination of 

 these elements much uncertainty prevails. Some chemists consider 

 them united equally with each other, and regard the organic prin- 

 ciples themselves as ternary or quaternary compounds of them. 

 But others have suggested a mode of combination more analogous 

 to that of inorganic substances (see page 5) ; namely, that two or 

 three of the elements form a compound radicle, with which the 

 remaining one unites to form a binary compound. In a body, for 

 example, consisting of three elements, two would form the com- 

 pound radicle, or, in one composed of four elements, three would 

 constitute it. This mode of composition has been rendered more 

 probable in the secondary organic products than in the true proxi- 

 mate principles ; and it may be illustrated by an example taken 

 from the former class. Ether is composed of four atoms of carbon, 

 five atoms of hydrogen, and one atom of oxygen ; the carbon and 

 hydrogen constitute a hypothetical compound radicle, called ethyl, 

 which is united with one atom of oxygen : so that ether is an oxide 

 of ethyl, and its formula may be expressed C 4 H 5 + O. 



Among the secondary organic products of the vegetable class we 

 meet a few instances of binary compounds of simple elements ; but 

 the great majority of proximate organic elements, whether primary 

 or secondary, are composed of three or four essential elements. 



In contrasting, then, the chemical composition of organic with 

 that of inorganic substances, we perceive, that, applying the binary 

 theory to both classes of substances, their mode of combination is 

 strictly analogous; there being, however, this distinction, that 

 among organic substances combination with a compound radicle is 

 the prevailing mode, and that the union of two simple substances is 

 rare. If, on the other hand, we adopt the theory of oxy-acid -salts 

 for inorganic compounds, and view the organic principles as ternary 

 or quaternary compounds of simple elements, each to each, then it is 

 evident that the most marked difference must exist between the two 

 classes of compounds, the latter being formed on principles entirely 

 dissimilar from those which regulate the composition of the former. 



It is probable, however, that the progress of Chemistry will shew 

 that the binary theory is applicable to both classes of substances, 

 and that the same mode of chemical composition prevails through 

 both kingdoms of Nature. 



If so much uncertainty exists in reference to the manner of 

 combination of the simple elements to form organic compounds, it 

 is no wonder that the attempts of chemists to produce them by 

 artificial processes should have met with so little success. No one 



