128 Dr. R. D. Thomson's Examination of the Cowdie Fine Resin. 



The influence of heat may lience 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 more temperate latitudes. 



DAMMAROL. 



When the Cowdie resin is exposed to the heat of a spirit-lamp, it 

 melts, and, by the continuation of not too high a temperature, heavy 

 vapours arise which gradually and slowly pass over, and condense in 

 the receiver in the form of a fine amber-coloured oil swimming on the 

 surface of water. It is obvious, therefore, that by this treatment the 

 resin has been resolved into dammarol and water. By evaporation 

 at 300°, the water disappears and the oil remains. It boils at a high 

 temperature. 5*98 grs. gave when burned with oxide of copper, 18*03 

 grs. CO2 and 6.02 HO. 



The composition of dammarol is, therefore, — 



Carbon, 82'22 



Hydrogen, 11*14 



Oxygen, 6*64 



10000 

 The following would be the composition if the formula were C40 

 Has O3, supposing that three atoms of water were detached from the 

 resin to form dammarol. 



Carbon, 82-19 .... 40 



Hydrogen, 9-56 . ... 28 



Oxygen, 8-25 .... 3 



100-00 



The analysis gives an excess of hydrogen, proceeding from the 

 retention of water. 



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

 (Memoires de V Academic Boyale des Sciences de Paris, 1688,*) and 

 the relative proportions of water and oil obtained by the distillation of 

 these bodies were accurately noted. Colophan or common rosin, for 

 example, it is stated when distilled in the quantity of two pounds, 

 afforded 26 ounces 4 drs. of oil, and 3 ounces 1 dr. of an acid liquor. 

 Neumann, a most sagacious chemical writer, whose works may even 

 yet be consulted with benefit by modem chemists, was well aware of 

 the nature of the products of the distillation of resins, and of the 

 derivation of resins from essential oils. ** Essential oils," he says, 

 "by digestion or heat, (Neumann^s CfJiemistry, by Lewis, 4<o, 1758, p. 

 269,) change into balsams, and at length into brittle resins. Distilled 

 again in this state, they yield like most of the natural resins, a portion 

 of fluid oil." 



* See also Collection de pieces Academiqws, Tome I. p. 141.— 1754. 



