Dr. Kane on the Composition of certain Essential Oils. 147 



cases. Of these few, the synthesis of urea, and that of acetic acid, may be taken 

 as illustrations. 2nd, The method next in completeness is the breaking up of the 

 body into other compounds whose composition is already known ; as, formal into 

 formic acid and methylic alcohol ; acetal into acetic acid and vinic alcohol ; acetic 

 acid into carbonic acid and acetone. 3rd, The determination of the atomic weight 

 of the body, by the compounds into which it enters with other well known sub- 

 stances. Thus the composition of oxalic ether controls the analysis of sulphuric 

 ether, and the salts of the vegetable alcaloids give the only means of verifying 

 the composition of the base itself. The fourth method of control is limited to 

 such bodies as pass into vapour without being decomposed, and then the density 

 of the vapour should stand in some simple relation to the sum of the densities of 

 the constituents, taken in the atomic proportions given by analysis. Thus the 

 discussion as to whether napthaline was represented by the formula c^ h.^ or Cg Hj 

 was decided by the vapour possessing a density immediately following from the 

 former, but inconsistent with the latter. That, however, we must not insist on 

 very simple relations, is shown by the complex numbers found for some of the 

 inorganic compounds by Mltscherlich and Dumas. 



Now in examining the composition of the oils, we are debarred from efficiently 

 exerting any of these methods of control: — 1st, we cannot generate them by 

 synthesis ; 2nd, we do not as yet know their chemical nature sufficiently to 

 break them up into other bodies with which we can get more definite results ; 

 and 3rd, their combinations with other bodies have not been as yet developed. 

 Towards the application of these methods I have made some progress in the 

 cases of oils of rosemary, lavender, and oil of turpentine, which all give with 

 sulphuric acid and a base, soluble salts, of which that from turpentine alone has 

 been completely analyzed. The atomic weight of turpentine from the salt of 

 lime is found to be c^o 11,6 ; the same as from artificial camphor ; and the salt 

 has the composition SO3 . cao . ■\- c^ H,g, belonging to a series distinct from the 

 sulpho-vinates on the one hand, and the sulpho-napthalates upon the other, and 

 being probably an analogue to the sulpho-mesitylic acid described in my memoir 

 upon Acetone. I mention these results, although they properly belong to a dif- 

 ferent paper, in order to point out the probable means of applying the methods 

 of control to the essential oils in future investigations. I attempted very often 

 to determine the densities of the vapours of the essential oils with a bath of 



