86 Dr. R. D. Thomson on the Cowdie Pine Resin. 



The influence of heat may hence account in some degree for 

 the more rapid formation of resins from oils of the turpentine 

 type in warm countries, and also for the greater solidity which 

 resins acquire than in the more temperate latitudes. 



Dammarol. 



When the dammara resin is exposed to a carefully regu- 

 lated temperature it melts, and heavy vapours arise, which 

 gradually and slowly pass over and condense in the form of 

 a fine amber-coloured oil swimming on the surface of water ; 

 hence by this treatment the resin is resolved into an oil, which 

 may be termed dammarol, and water. By evaporation at 

 300° the water is dissipated and the oil remains. It boils at 

 a more elevated temperature than water. After rectification, 

 5*98 grs. burned with oxide of copper gave 



18-03 grs. CO s and 6 -02 HO, 

 which makes the composition of dammarol, — 



Carbon 82*22 



Hydrogen H'14 



Oxygen 6'64< 



Too- 



This approximates 



^40 "28 ^3> 



and when compared with dammaran — 

 Dammaran . . . C^ H 31 O e 

 Dammarol . . . C 40 H 28 3 



H 3 3 = 3 HO 

 shows the removal of 3 atoms of water. The analysis gives 

 an excess of hydrogen from the retention of some water. 



The action of heat upon resins was known as early as 1688 

 (Memoires de VAcademie Hoy ale des Sciences de Paris, 1688), 

 and the relative proportions of water and oil obtained by the 

 distillation of these bodies was accurately noted. Colophon or 

 common resin, for example, it is stated, when distilled in the 

 quantity of 2 pounds, afforded 26 ounces 4 drachms of oil, 

 and 3 ounces 1 dr. of an acid liquid. Neumann, a most sa- 

 gacious chemical writer, whose works may even yet be con- 

 sulted with benefit by modern chemists, was well aware of the 

 nature of resin. " Essential oils," he says, " by digestion or 

 heat (Neumann's Chemistry, by Lewis, 4to. 1758, p. 269) 

 change into balsams, and at length into brittle resins. Di- 

 stilled again in this state they yield, like most of the natural 

 resins, a portion of fluid-oil." 



The effect of heat in removing water from resin, as now 

 stated, enables us to explain the process for preparing copal 



