GENERAL VIEWS. 337 



stances, which are yet so widely different in their pro- 

 perties. Vinegar differs from alcohol, for example, in 

 containing a little more oxygen and a little less hydro- 

 gen, while the proportion of carbon in each is the same. 

 Ether, also, contains the same amount of carbon as the 

 alcohol from which it is formed, with a little less hydro- 

 gen and oxygen. Yet these substances are all widely 

 different in their properties. 



Mention some 855. IDENTITY OF COMPOSITION. Most 



hichr*difi remarkaole f all > and at first view incred- 

 ferent in pro- ible, is the fact that many organic sub- 

 tdenticaHn stances which are as widely different in 

 composition. properties as any which have been named, 

 are still precisely the same in their composition ; not 

 alone containing the same elements, but containing 

 them in precisely the same proportion. The most careful 

 chemical investigation finds no difference of composition 

 in wood, gum, and starch. The sugar which sweet 

 milk furnishes, arid the acid which exists in the sour, 

 contain identically the same proportions of the same 

 constituents. The oils of turpentine, lemon and pepper, 

 so different in their taste, contain an equal quantity of 

 carbon and hydrogen, without the addition of any 

 third substance to either, to account for the difference. 

 Truly, organic chemistry has brought us to results as 

 strange as the dream of the alchemist, who believed 

 that lead might be converted into silver, and copper 

 into gold. All such substances, possessing the same 

 composition with different properties, are called iso- 

 meric bodies a term signifying their similarity of com- 

 position. 



15 



