Easterfield and Bagley. — Chemistry of Colophony. 477 



(1.) Colophony consists principally of organic acids, of 

 which one, abietic acid, is in preponderating proportion. 

 The use of rosin in soap-making depends upon its acidic 

 nature. 



(2.) Kosin, when distilled at ordinary pressures, yields a 

 very composite mixture of substances, consisting chiefly of 

 hydrocarbons, the more volatile portions of which are known 

 as " rosin-spirit," the less volatile as " rosin-oil." The oil 

 is largely used in the preparation of lubricants for heavy 

 machinery. Rosin-oil consists very largely, according to 

 Deville, of a hydrocarbon the percentage composition of 

 which approximates to that of turpentine, but the molecular 

 weight of which is much greater. It is generally regarded 

 as a diterpene. 



(3.) When distilled under diminished pressure, rosin is 

 said to yield an anhydride of an acid isomeric with abietic 

 or sylvic acid, together with a hydrocarbon, probably the 

 " colophene " of Deville. This statement is due to Bischoff 

 and Nastvogel. The authors greatly regret that their work 

 has led them to conclusions of a totally different nature. 



Put shortly, the results of the present investigation may be 

 thus stated : — 



(1.) When colophony is fractionally distilled under di- 

 minished pressure a small quantity of turpentine and other 

 hydrocarbons distil first. The greater part of the rosin then 

 comes over in an unchanged state, between 260-285° C, 

 at 15 mm. pressure. This is nearly pure abietic acid. 

 Lastly, there is a small quantity of pitch, which has so far 

 defied all attempts at investigation. The distillation of colo- 

 phony under diminished pressure is an excellent method of 

 obtaining crude abietic acid ; for the middle portion of the dis- 

 tillate, when twice crystallized from alcohol, yields practically 

 pure abietic acid melting at 163-165° C. 



(2.) If the distillation be conducted slowly, the early 

 portion of the distillate increases in quantity, whilst the 

 second portion diminishes. The pitch increases at the same 

 time. Careful examination of these facts has shown the 

 authors that this change in the yield, with the altered con- 

 ditions, is due to the fact that the hydrocarbon is produced 

 from abietic acid according to the equation — 



CigH^Oa = C 18 H 28 + C0 2 . 

 This hydrocarbon, though evidently identical with that found 

 by Deville in 1841 amongst the products of the distillation of 

 colophony,* is not, as has hitherto been supposed, a diterpene, 

 but appears to be a member of a special series. The name 

 abietene is proposed for this compound. The authors have 



* See Liebig's " Annalen," 37, 193. 



