— 37 — 
unlike the rather strongly dextrogyrate raw material. This laevorotation 
has always been considered as particularly characteristic for terpene- 
less lemon oil, indeed a rotation of at least — 7^ to — 8^ was 
insisted upon for this preparation. 
Among the compounds met with in concentrated lemon oil are 
optically active only citronellal, terpineol, linalyl acetate and the sesqui- 
terpene, the latter being known to rotate, though not in which direction; 
of these bodies citronellal is dextrogyrate, whereas terpineol and linalyl 
acetate turn the polarised light to the left, the former doing so less 
than the latter. The content of terpineol and linalyl acetate in con- 
centrated lemon oil is not very considerable and it may therefore be 
safely supposed that the laevorotation caused by these bodies is at 
least counterbalanced bv the dextros^vration of the citronellal, the likelv 
consequence being optical inactivity or even slight deviation to the right. 
These reflections lead forciblv to the conclusion that the Isevo- 
rotation, claimed up to the present so persistently for terpeneless 
lemon oil, must be attributed exclusively to its sesquiterpene-content. 
How^ever, if lemon oil is freed from its terpen es, in order to in- 
crease its solubility and prevent certain troubles, it is but logical to 
remove also the sesquiterpene, same impeding likewise the solubility 
of lemon oil. But on separating the sesquiterpene a concentrated 
lemon oil is obtained, the properties of which differ from those required 
up to now for terpeneless lemon oil, the most remarkable event being 
the changed rotatory powder. 
Terpeneless lemon oil, in the true sense of the word, will always 
be laevogyrate, whereas oils freed from terpenes and sesquiterpene 
should be either optically inactive or slightly dextrogyrate. It wdll 
indeed soon be found in practice that the sesquiterpeneless preparation 
deserves the preference, for it is already soluble in about 6 to 10 parts 
60 per cent, alcohol, whereas terpeneless oil requires often twice as 
much if not more of 70 per cent, alcohol. 
On this occasion we ascertained the sesquiterpene of lemon oil 
to belong to the category of the light sesquiterpenes, its physical 
constants being: — boiling point 125° to 127° (8 mm pressure); 
d^5 0 0,8843; — — 42° and vlj^^^o = 1,49034. So far we have 
not succeeded in obtaining crystallised derivatives by means of which 
this hydrocarbon might be identified. 
Mandarin Oil. It is well known that a few years ago H.Wal- 
baum^) succeeded in identifying in our laboratory the fluorescent 
constituent of oil of mandarin peel as methyl ester of methyl anthran- 
ilic acid. E. Charabot^) has recently found that the same body is 
^) Report October 1900, 31. — Journ. f. pract. Chemie 11. 62 (1900), 135. 
^) Compt. rend. 135 (1902), 580. 
