Dr. R. D. Thomson on the Cowdie Pine Resin. 83 



To determine whether the resin was sufficiently dried, a por- 

 tion was fused and exposed to a temperature 6f 350° for some 

 time. The following were the results of two analyses : — 

 I. 6*97 grs. gave 19*30 grs. C0 2 and 6-18 HO 



II. 7'96 6-93 HO 



This is equivalent to 



I. II. Mean. 



Carbon . . . 75-46 75*46 



Hydrogen . 9*85 9*67 9*76 



Oxygen . . . 14*69 14*78 



100* WO' 



From these data we may deduce the following composi- 

 tion: — 



Calculation. Experiment. 

 Carbon . . *75* x 40 = 30* =75*23 75*46 

 Hydrogen- *125 x 31 = 3875 . 9*73 9*76 



Oxygen. . 1* x 6 = 6* 15*04 14*78 



39*875 100* 100* 



The close correspondence of the theoretical and practical 



results, in reference more especially to the hydrogen, may lead 



us with some degree of confidence to assume the following 



formula as representing the composition of the cowdie resin : — 



C 40 H 31 O e ; 

 and adopting an analogous view to that of Liebig, in refer- 

 ence to the composition of turpentine resins, we may consider 

 the basis of the resin — 



C40 "30 fj 



becoming, by the substitution of one atom of oxygen for one 

 of hydrogen, and the addition of oxygen, 



QlO Hgo Q •+■ 3 . 



Hydrous Dammaric Acid. 



The resin was boiled in successive portions of alcohol un- 

 til it ceased to lose more of its substance. The solution was 

 then precipitated by water. The precipitated resin was wash- 

 ed and dried at 212°, but not fused. 



* Dr. Thomson first deduced '75 for the atom of carbon (in 1813) from 

 the specific gravity of carbonic acid, and from his analysis of olefiant gas. 

 In the same year he fixed "878 as the atom of azote. Now this number is 

 almost exactly half of his present number, for -878 X '"2 = 1*756. It may 

 not be out of place to mention, that in his recent works on organic che- 

 mistry he has recalculated all the formulae of the foreign chemists by his 

 own atomic weights, which have been recently so strikingly confirmed by 



Dumas and others. 



G2 



