90 Prof. Johnston on the Composition of certain 



cold alcohol or aether, giving brown solutions. A small re- 

 sidue of earthy impurities is left. By evaporating the alco- 

 holic solution, the resin is obtained of greater transparency, 

 transmitting light of a bright red colour, fusing easily on the 

 water-bath, and remaining soft and unctuous at the ordinary 

 temperature of the atmosphere. It gradually recovers its 

 brittleness, but after the lapse of three or four months it is 

 still soft, and adlieres in some measure to the fingers. This 

 property appears to be possessed by many other resinous 

 substances and explains the semifused appearance of the im- 

 ported masses. 



It has a peculiar, unpleasant, resinous odour. After fusion 

 for some time at 212° Fahr., the unpleasant odour disappears, 

 and is succeeded by an agreeable fragrance. On cooling again, 

 it resumes after some time its original smell. When chewed 

 in the mouth it imparts a slight sensation of bitterness ; but 

 the alcoholic solution has a disagreeable very bitter taste. 



Like most other resins it is nearly insoluble in a concen- 

 trated solution of caustic potash. Boiled in more dilute al- 

 kali it gives a yellow solution, from which the resin is again 

 precipitated by acids. The alcoholic solution gives with a si- 

 milar solution of acetate of lead a copious yellow precipitate. 

 It is therefore an acid resin. Its alcoholic solution is rendered 

 milky by liquid ammonia and passes milky through the filter. 

 Burned with oxide of copper 

 1 2*733 grs. gave 33'37 of carbonic acid and 10*5t of water. 

 12*4'0 grs. gave 32'44< of carbonic acid and 10*445 ofwatei*. 

 These are equivalent to 



1, 2. 



Carbon 72*472 72*338 



Hydrogen 9-198 9*359 



Oxygen 18*330 18*303 



100*000 100*000 



These results agree very nearly with the formula C40 H31 Og, 

 which gives 



40 Carbon... = 3057*480 = 72*036 

 31 Hydrogen = 386*8676 = 9*115 



8 Oxygen ... = 800-000 = 18*849 



4244*3476 100*000 



and represents a constitution analogous to that of colophony 

 and some other resins of which oil of turpentine is the radical. 

 But as the quantity of carbon indicated by this formula is 

 less than that found by analysis, we ought probably to prefer 

 one or other of the two formulae 



