Dr. R. D. Thomson's Examination of the C(ywdie Fine Resin. 127 



Hence the formula of the anhydrous acid corresponds with 



C4S Hm 0« 



and the silver salt is, 



Bidammarate of silver 2 (C43 H^ Oe) + A^ O 

 Or if we view the analysis as giving an excess of hydrogen, the com- 

 position of the anhydrous acid would be as follows : 



40 X -75 = 30- 75-47 



30 X -125 = 3-75 9-44 



6x6- =6- 1509* 



39.75 10000 

 The formulae would then be 



Hydrous Acid Cm H^ OJ 



Anhydrous Acid, . . . C40 ^» O^ 



H 0=H0 

 the difference being an atom of water. 



DAMMARAN. 

 I give this name to the substance remaining after the separation 

 of the dammaric acid. It is a fine white brittle resin, apparently 

 insoluble in weaker spirit, but forming with absolute alcohol a beautiful 

 colourless varnish, and also, a similar preparation with oil of turpentine. 

 This substance appears to be identical in composition with the resin. 

 When dried at 212°, (100 C.) its composition was found to be as fol- 

 lows : — 



7'4 grs. gave wiien burned with oxide of copper, CO2 20*36, HO 6'4. 

 This is equivalent to, 



Carbon 75*02 



Hydrogen, 9*60 



Oxygen, 1538* 



100-00 

 If we compare this with the formula, €4^ H,, Og, we shall find that 

 it corresponds very closely. 



By exposing this substance to a higher and longer continued heat, 

 it was found to absorb oxygen pretty rapidly, and to alter, of course, 

 in its composition, as appears by the two following analyses : — 

 L 6-57 grs. gave 1675 CO, and 57 HO. 

 II. 7*64 grs. gave 20*33 CO^ and 6*7 HO. 



Dried at 300* for 3 days. Dried at 350° for 4 days. 



Carbon, . . . 72*56 . 69*25 



Hydrogen, . . 9*74 10*32 



Oxygen, . . . 17*70 20*43 



100*00 100*00 



* By Mr. David Miller, Laboratory Assistant. 



