84- Dr. R. D. Thomson on the Cowdie Pine Resin. 



6*9 grs. gave when burned with oxide of copper, 18*39 C0 2 

 and 5-78 HO. 



The composition of the hydrous acid is therefore — 



Experiment. Calculation. Atoms. 



Carbon . . . 72*69 7339 40 



Hydrogen . . 9*31 9*47 31 



Oxygen . . . 18*00 17*14 7 



100* 100* 



This approaches the formula 



^40 "* ^7* 



If the alcoholic solution of the dammaric acid be allowed 

 to evaporate spontaneously, the resin is deposited apparently 

 in the form of crystalline grains. 



Anhydrous Dammaric Acid. 



To determine the atomic weight, a solution of dammaric 

 acid in alcohol was mixed at a boiling temperature with an 

 alcoholic solution of nitrate of silver, to which some caustic 

 ammonia had been added. 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. 

 100*00 101*02 



To determine the composition of the anhydrous acid, the 

 silver salt was analysed. 



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

 C0 2 and 5*39 HO. 



The composition of the silver salt is therefore, — 



Carbon 64*78 65*45 Atomic weight. 



Hydrogen 9*01 9*11 86*27, or 



Oxygen 11*61 11*72 43 * 13 * 2 - 



Oxide of silver . . 14*30 14*75 

 100* 101*02 



And that of the anhydrous acid is — 



Experiment. Calculation. 



Carbon . . . 75*85 43 X *75 = 32*25 75*43 

 Hydrogen . 10*56 = 36 x *125 = 4*5 10*52 



Oxygen . . 13*59 6x6- =6* 14*05 



100*00 42*75 100* 



Hence the formula of the anhydrous acid corresponds with 



**^<13 ™36 Og'» 



