126 Dr. R. D. Thomson's Examination of the Cotvdie Pine Resin. 



HYDROUS DAMMARIC ACID. 

 The resin was boiled in successive portions of alcohol, until the 

 latter ceased to dissolve any more of it The solution was then pre- 

 cipitated by water. The precipitated rosin was washed and dried at 

 the temperature of 212^ F. (100° C.) but not fused. 

 6*9 grs. gave when burned with oxide of copper 



18-39 grs. CO2 and 5-78 grs. HO. 

 The result is therefore for the hydrous acid :— • 



Experiment. Calculated. 



Carbon, . . . 72-69 . . 73-39 . . 40 atoms. 

 Hydrogen, . . 931 . . 947 . . 31 

 Oxygen, . . . 1800 . . 17-14 . . 7 



100-00 100-00 



This approaches the formula C40 H3, O7. 



If the alcoholic solution of the dammaric acid be allowed to evaporate 

 spontaneously, the resin is deposited apparently in the form of crys- 

 talline grains. 



ANHYDROUS DAMMARIC ACID. 

 To determine the atomic weight, a solution of dammaric acid in 

 alcohol was mixed with an alcoholic solution of nitrate of silver, to 

 which some caustic ammonia had been added, at the boiling tempera- 

 ture ; the silver salt after being washed and dried was analysed ; — 



4-26 grs. gave by ignition -58 Silver = '622 Oxide of Silver. 

 From which we have — 



Oxide of Silver, .... 14-60 14-75 1 atom. 

 Dammaric Acid, . . . 85-40 86*27 2 atoms. 

 To determine the composition of the anhydrous acid, the silver sal 

 was analysed. 



6*62 grs. gave when burned with oxide of copper, 15-73 CO2 

 and 5-39 HO. 

 The composition of the silver salt is, therefore. 

 Carbon, . . . 64.78 65-45\ 



10000 42-75 100-00 



