Easterfield and Bagley. — Chemistry of Colophony. 483 



Boiling-point. Pressure. Weight of Distillate. 



241-250° 80-85 mm. 8-3 per cent. 



250-253 81mm. 63 7 



256-272 81mm. 6-9 



Eesidue = 3-9 per cent. 



Acid recovered from washings = 14 per cent. 



Loss = 3-2 per cent. 



The fraction boiling at 250-253 was redistilled several 

 times over sodium. When analysed different samples gave 

 numbers agreeing with those already given for the compound 

 prepared from crystallized abietic acid. Different specimens 



gave :— 



Calculated for -r -rj y T y 



CisH.jg. 



C = 88-5 88-3 88-2 88-5 88-7 

 H = ll-5 11-1 10-9 11-0 11-3 



Further evidence of the identity of the two substances is 



shown by the similarity of their physical constants. 



TX , , , .,. ,. , ., Hvdrocarbon from Crude 



Hydrocarbon from Abietic Acid. ' Rosin 



Specific gravity 0-9728 at 19° C. 0-9727 at 18° G 



Eefractive index 1-537 „ 20° C. 1-538 „ 12° C. 



(199-200 „ 13 mm. 

 Boiling-point 247-250 „ 82 mm. \ 253-255 „ 82-85 mm. 



(340-345 „ 760 mm. 



The hydrocarbon from crude rosin is optically active. It 

 gave the value [a] d = 92-9. 



In 1884 Liebermann* obtained a hydrocarbon approxi- 

 mating in composition to that of a terpene by heating abietic 

 acid with hydriodic acid and phosphorus at a temperature of 

 240° C. It appeared of great interest to learn whether the 

 formation of this hydrocarbon was due to the reducing-action 

 of hydriodic acid, or, as it appeared more probable, to the 

 sphtting-off of carbon-dioxide. Experiment showed that the 

 latter hypothesis was the corrct one. 



Five grams of abietic acid was heated in a sealed tube with 

 20 c.c. of fuming hydriodic acid for six hours at a temperature 

 of 210-230° C. The gas which collected in the tube consisted 

 largely of carbon-dioxide, and the abietic acid was transformed 

 into a hydrocarbon. This was purified in the usual Way. It 

 was then found to boil for the most part at 245-255° C. at 

 84 mm. pressure. The quantity of material was insufficient 

 for a complete purification ; but the analytical results and 

 physical constants leave little doubt that the product of the 

 action of hydriodic acid is identical with that formed by the 

 distillation under diminished pressure. The analyses gave : — 



* Berichte, 17, 1885. 

 31 



