68 SCIENCE PROGRESS 



Here again a variety of substances are employed — air, ozone, 

 chlorine, nitric acid, potassium dichromate and sulphuric acid, 

 potassium permanganate, and many others. Lastly, the crude 

 camphor must be refined by one of the methods already de- 

 scribed for natural camphor ; i.e. by steam distillation, subli- 

 mation, or crystallisation. 



The patents in connection with the manufacture of synthetic 

 camphor, of which a considerable number are being taken out 

 at the present time, consist chiefly of — 



(i) Variations in the manner of splitting off hydrochloric 

 acid from pinene hydrochloride. 



(2) The use of other esters than the acetate of borneol, 



e.g. formate, oxalate. 



(3) Different oxidising agents for the conversion of borneol 



to camphor. 



A few patents seek, by heating with organic acids, to pass 

 direct from pinene to borneol without passing through the 

 pinene hydrochloride stage, but those processes which adopt 

 the course detailed above seem to be the best. 



The synthetic production of camphor thus involves a series 

 of six distinct operations before the final article is obtained — 

 turpentine -> pinene -> pinene hydrochloride -> camphene -> 

 bornylacetate -> borneol -> camphor. 



Synthetic camphor is now being manufactured by a number 

 of firms. It represents one of the best and most recent ex- 

 amples of the growing tendency (due to scarcity of raw 

 materials) to replace natural products by artificially prepared 

 substances, which are either identical with, or can be used as 

 substitutes for, the naturally occurring body. Indiarubber 

 presents a similar problem not yet successfully solved. 



Assuming a good supply of turpentine at moderate price, 

 there is little doubt that synthetic camphor which is quite equal 

 in all respects to its Oriental rival has a good future before 

 it, and will be able to compete successfully with Japanese 

 camphor. 



