Prof. Johnston on Minerals of Organic Origin. 561 



weight ; at 320° Fahr. it is perfectly fluid, and at 400° it gives 

 off' minute bubbles as if slowly effervescing. 



6-885 grs. dried at 212"^ raised to 25o" had lost 0*06, to 

 320° —0-09, and to 400° ~0-24< gr. 



Dried at 212° and burned with oxide of copper 6*492 grs. 

 gave water 5*11, carbonic acid = 18*045. 



Heated to perfect fusion 7*i29 grs. gave water = 5*58, car- 

 bonic acid = 20*41 grs. 



These results are equivalent to 



Dried at 212°. At SOO^. 



Carbon = 76*860 77*414 



Hydrogen ... = 8*749 8*508 



Oxygen = 14*395 14*078 



100* 100- 



Calculated according to the formula C^ H5 O, we have 



7 Carbon ... = 535*059 = 76*716 per cent. 

 5 Hydrogen^ = 62*398 = 8*946 

 1 Oxygen... = 100000 = 14*338 



697*457 100* 

 This formula is beautifully simple, but the hydrogen found 

 by experiment is obviously too little to warrant us in adopting 

 it. The true constitution, therefore, I believe to be Cgj Hj, 

 O3 , giving 



21 Carbon ... = 1605*177 = 77*171 percent. 

 14 Hydrogen = 174*7144 = 8*400 

 3 Oxygen... = 300*000 = 14*429 



2079-8914 100* 



which allows for the presence of a little moisture in the oxide 

 of copper. 



This constitution is corroborated by two experiments, in 

 which the combustion was imperfect, but which gave the car- 

 bon and hydrogen respectively, in the proportions of 

 Atoms 

 3 Carbon to 2*066 Hydrogen. 



3 2*143 



As the nature of the retinic acid and the circumstances 

 under which it occurs lead us to refer its origin to some tree 

 belonging to the family of pines, we should expect to find 

 some relation between its constitution and that of the colo- 

 phonies, or pine resins of recent production. 



According to Heinrich Rose, crystallized gum 

 Elemi consists of Coq Hj^j O, and 



crystallized Colophony of 4 (Cjo Hg) -f 40, 



Phil. Mag,, 5. 3., Vol. 12, No. 78. SuppL July 1838. 2 Z 



