1915] ISOPKENE FROM CoMMEECIAL TuKPENTINES 153 



ISOPRENE EROM COMMERCIAL TURPENTINES* 



BY CHAS. H. HERTY AiSfD J. O. GRAHAM 



In connection with the studies of rubber made by polymeri- 

 zation of isoprene, Harries and Gottlob ^ described a method for 

 the preparation of isoprene from spirits of turpentine by means 

 of the '' isoprene lamp." in this method the spirits of turpen- 

 tine is boiled in a flask, in which, just below the neck, is suspend- 

 ed an electrically heated platinum wire coiled somewhat like the 

 hlament of a tantalum incandescent bulb. A part of the vapors 

 are decomposed as they pass upward across the heated wire. The 

 Hask is attached to an upright condenser maintained at a temper- 

 ature of 50° C, for condensing the unchanged vapors of spirits 

 of turpentine. The upright condenser is connected with an in- 

 clined condenser fed with tap water and this in turn is connected 

 with a receiver surrounded by a freezing mixture. The crude 

 product collected in this receiver is fractionated and the isoprene 

 collected as the fraction boiling between 35° and 37° C. 



With this apparatus, Harries and Grottlob obtained a yield of 

 only 1 per cent of isoprene from commercial pinene as against 

 30 to 50 per cent from commercial limonene. They, therefore, 

 concluded that the yield of isoprene from spirits of turpentine 

 is due chiefly to the presence of dipentene (limonene). 



In view of the general interest in the production of rubber 

 from isoprene, it seemed desirable to extend these studies to 

 commercial products closely related to spirits of turpen- 

 tine and to test further the point mentioned above as to 

 the origin of the isoprene from spirits of turpentine, accord- 

 ingly, studies have been made using commercial spirits of tur- 

 pentine, fractions of the same, pine oil, the volatile oil of Pinus 

 serotma (pond pine) and refined spruce pine teurpentine. 



The apparatus used closely resembled that of Harries and 

 Gottlob, short-circuiting of the sections of red hot platinum wire 

 being prevented by winding the wire on a pipe stem triangular 



* Reprinted from the Journal of Industrial and Engineering Chemisty, Volume 

 6, No. 10, page 803. October, 1914. 



Presented at the 48th Meeting of the American Chemical Society, Rochester, 

 September 8-12, 1913. 



^Ann., 383, 228. 



