5° 



On the strength of the experience obtained by us with the resorcinol 

 method, we can recommend it as useful. Over the two first -named 

 methods it has the advantage not only of reliability, but also of a 

 much more simple manipulation. It has also this advantage that the 

 resorcinol can again be readily recovered and used afresh. It is only 

 necessary to treat the solution (preferably previously freed from the 

 oil which has not entered into reaction) with steam, when the 

 resorcinol cineol is split up, and cineol distils over. The residue is 

 then evaporated to dryness, and the resorcinol remaining behind is again 

 ready for use. 



As stated above, a concentrated solution of resorcinol dissolves, 

 besides cineol, also other constituents of eucalyptus oil. We are at 

 present occupied in investigating the influence exercised thereby on 

 the exactness of the new method, and shall give further information 

 in our next Report. 



The determination of the bromine number which Mossier 1 ) employs 

 for judging the value of eucalyptus oil, is based upon the reaction of 

 the less important, non-cineol-like constituents of the oil with bromine, 

 so that the best quality oils, with the highest cineol-content, give the 

 lowest bromine number. If the absence of possible admixtures of 

 hydrocarbons which are apt to lower the bromine number, has been 

 determined, it is possible, according to Mossier, in comparative 

 examinations, to state that the oil is the richest in cineol which 

 shows the lowest bromine number, as in the case of pure cineol the 

 action of the bromine according to Mossier 's method causes no 

 addition or substitution; the bromine number allowed for cineol should 

 not exceed 2. 



We have checked Mossler's method on some oils whose cineol- 

 content had been determined by the resorcinol method, and obtained the 

 following results: — 



Oil of 



d i5° 



ajy 



Cineol 

 content 



% 



Bromine 

 number 



Soluble in 



/. E. Globulus 



0,9186 



+ o° 



82 



51,6 



2,2 vol. 70 per cent, alcohol 



U. 

 Ill 



IV. E. amygdalina 



0,9185 

 0,9142 

 0,867 



+ i°i3' 

 + o° 4 o' 

 — 43° 4o' 



71 



" 82 



29 



71,0 



56,7 



161,5 



3,o h 7o „ 



2,5 » 7o ,, „ 

 0, 5 and more vol. 90 per cent, 

 alcohol, with opalescence 



v. 



0,863 



-6o°2 5 ' 



21 



157,8 



0,5 and more vol. 90 per cent, 

 alcohol, with opalescence 



VI. E. rostrata (?) 

 (Algerian oil, free 

 from phellandrene) 



0,914 



.+ 4°55' 



77 



58.5 



about 7,0 vol. 70 per cent, 

 alcohol 



*) Comp. the present Reports, under Analytical notes. 



