A CENTURY OF CHEMISTRY. 101 



composition, but are very different in character. 

 In 1825 Faraday showed that butylene has the same 

 composition as ethylene (olefiant gas), though the 

 former has twice the specific gravity of the latter. 

 In 1830 Kestner showed that racemic acid has the 

 same composition as tartaric acid, and hundreds of 

 such cases are now known. These facts at first served 

 to complicate matters; they showed that compounds 

 with widely different properties may contain the same 

 constituents and in the same proportions. Berzelius, 

 in labelling the puzzle with the term isomerism, 

 suggested, as Dumas also did, that the component 

 atoms must " be placed together in different ways " 

 in the various isomers, which were the same in com- 

 position and yet different in properties. The sug- 

 gestion seems an easy one, especially when we note 

 that " one chemical compound, a hydrocarbon con- 

 taining thirteen atoms of carbon combined with 

 twenty-eight atoms of hydrogen, can be shown to be 

 capable of existing in no less than 802 distinct 

 forms'' (Roscoe). Indeed, possible substances have 

 been repeatedly predicted, and afterwards discov- 

 ered or made. But for forty years from Berzelius 

 and Dumas there has been a succession of attempts 

 to show how we may reasonably conceive of compo- 

 sition being the same while the constitution and re- 

 sulting properties are different. It seems likely that 

 the solution is to be found in the modern develop- 

 ment which is called " Chemistry in Space." 



Radicals. — But another step with which Wohler 

 was associated, along with Liebig, Bunsen, Dumas, 

 and others, was the formulation of the radical 

 theory. It was well known that salts are formed 

 from an acid and a base and can be decomposed into 

 these two constituents. For an understanding of the 



