66 SCIENCE PROGRESS 



by combining acid bornyl phthalate with an alkaloid, separating 

 the active salts by fractional crystallisation, and then saponifying 

 each, whereby the optically active modifications of borneol are 

 obtained. 



It is necessary to keep the true synthetic camphor quite 

 distinct from the so-called " artificial " camphor, which indeed 

 is not camphor at all, but simply the hydrochloride of the 

 terpene pinene, C 10 H 16 . HC1. Its odour slightly resembles that 

 of camphor, but it is of course a totally different substance. 

 The synthetic production of camphor starts out from turpentine, 

 the resinous liquid which exudes from various Coniferce} 

 When turpentine is distilled, oil of turpentine passes over and 

 the resin colophony remains behind. The oil of turpentine is 

 then carefully fractionally distilled. The portion boiling at 

 155 — 160 C. (90 per cent, of a good sample) consists chiefly of 

 the hydrocarbon pinene, C 10 H 16 (formula X.). Well cooled 

 pinene, when saturated with dry hydrochloric acid gas, is con- 

 verted into pinene hydrochloride (XI.) (the "artificial camphor" 

 above noted), which is thrown out as a white crystalline mass. 

 The next step in the process consists in splitting off hydro- 

 chloric acid from the pinene hydrochloride. A hydrocarbon 

 C 10 H 16 is obtained, not however the pinene from which we 

 started, but the isomeric camphene (formula XII.). It will be 

 observed that the double bond has moved from the position 

 1 '2 to the position 2*3; i.e. the hydrochloric acid has been split 

 off from a different part of the molecule from that which it 

 entered. It is worthy of note that camphene is the only solid 

 terpene hydrocarbon. It is a white solid, melting at 50° C. 

 This elimination of hydrochloric acid and consequent conversion 

 of pinene hydrochloride to camphene may be accomplished in 

 a great variety of ways. A few may be mentioned : 



1. Heating with ammonia or with organic bases such as 

 methylamine, pyridine, quinoline, piperidine, piperazine. 



2. Heating with caustic soda and a salt of a higher fatty 

 acid (soap), such as stearates of sodium, lead, copper, etc. 



3. Heating with phenolates or naphtholates of sodium, 

 potassium, calcium, magnesium, etc. 



1 The pine species which provide most of the turpentine are — in America 

 Pinus palustris, in France Finns maritima, and in Russia Pinns sylvestris. 

 Russian turpentine contains much less pinene than French or American, and 

 is not suitable for making pinene hydrochloride. 



