THE CHEMICAL HISTORY OF THE 



TERPENES 



A CHAPTER IN MODERN SYNTHETICAL 



CHEMISTRY 



By SIR WILLIAM A. TILDEN 



The hydrocarbons known as the terpenes have long attracted 

 the attention of chemists, on account of their wide diffusion in 

 the vegetable kingdom and their frequent association with the 

 odorous principles of plants, though it is only during the last 

 thirty to forty years that systematic research has been rewarded 

 with such a measure of success that it can be said that the 

 properties and chemical constitution of all the more important 

 members of the group are now as well understood as those of 

 any other group of carbon compounds. 



The terpenes are highly interesting from two distinct points 

 of view. As already mentioned, they are important for com- 

 mercial reasons not only on account of the use of some of them 

 as solvents, especially the oils of turpentine in varnishes and 

 paints, but they are characteristic and often predominant con- 

 stituents of many essential oils used in medicine and perfumery. 

 They have also been made the starting-point for the manu- 

 facture of certain substances — camphor and terpineol, for ex- 

 ample, which are extensively used for such purposes. 



But the history of the investigations by which the chemical 

 constitution of many of the terpenes has at last been elucidated 

 is specially interesting to the scientific chemist on account of the 

 nature of the problems to be solved, the peculiar elusive trans- 

 formations of the hydrocarbons and their derivatives and the 

 ultimate success of these investigations, which provides a 

 triumphant vindication of the principles which underlie modern 

 synthetical chemistry. These principles concern not only the 

 student of " organic " chemistry, for they are necessarily in- 

 volved in general conceptions regarding the constitution of 



matter. 



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