154 Journal of the Mitchell Society [Jan. 



prism. A constant current of 2.25 amperes maintained an even 

 temperature of the wires at a red glow. The flask containing 

 the turpentine was heated by means of a bath of cottonseed oil 

 containing a thermometer. The receiving vessel in the freezing 

 mixture, salt and ice, was a small sulfurous acid condenser. The 

 crude products were refined by distillation through a Hempel 

 column filled with glass beads. The yield of pure isoprene in 

 each of the experiments which follow represents the fraction 

 collected between 35° and 37° C. 



SPIRITS OF TURPENTINE 



200 cc. of spirits of turpentine were boiled in the isoprene 

 lamp until condensation ceased in the inclined condenser. At 

 two-hour intervals the crude product was removed from the 

 receiver and fractionated. Following this experiment, similar 

 experiments were conducted with 200 cc. fractions of spirits of 

 turpentine obtained by fractionation by means of a Young's 

 still head. The first fraction was collected between 155° and 

 156° C, the pinene fraction; the second, between 169° and 

 175° C. ; the third fraction from 175° C. up. These two last 

 fractions should include the dipentene content of the original 

 spirits of turpentine. 



The heating of the two last fractions was continued only two 

 hours, as after that time no further condensation could be ob- 

 served in the inclined condenser. 



The results of the three experiments are shown in Table I : 



Table I Volume 



Volume of of res- 



Time distillate Idue in 



of Temper- ^-—^.--^^.-^ Per cent heat'g 

 Substance heating ature of Crude Refined of flask 



used Hrs. oil bath Cc. Cc. isoprene Cc. 



2 175° 17 6.5 3.25 



Spirits of turpentine 2 175° 12 3.5 1.75 



2 185° 8 1.0 0.50 103 



Totals ~6 TTT 37 ILO TSO "T03 



Fraction 155° — 156° 



2 175° 10 6 3.00 



2 175° 7 5 2.50 



2 175° 6 4 2.00 



2 175° 4 1 0^ ... 



Totals ~8 TTTT 27 16~ "s^OO ~50 



Fraction 169°— 175° 2 180° 6.5 1 0.50 192 



Fraction 175°+ 2 185° 3.25 0.00 195 



