— 34 — 
render the presence of 1-camphene in lemon oil probable. This surmise 
has since been confirmed by the chemists of the London Essence Co. 
In a fraction boiling at 164° (759 mm), (d = 0,869; «d = — 22°; 
Hp^go =1,4470), they were able to detect camphene by converting 
it into isoborneol; the melting point of the isoborneol obtained by 
them lay at 205^. 
The experiments made in our laboratory with the same substance 
gave identical results. 
With regard to pinene, the above-mentioned chemists believe that 
lemon oil contains not only 1-pinene, but also an almost inactive mixture 
of both modifications; they, however, produce no proofs in support 
of this. 
Parry 2) protests against the practice recently introduced by several 
firms of guaranteeing a citral- content of 7 per cent, in the lemon oil 
sold, whereas in reality the content of citral is much lower. These 
views of Parry, which are also supported from various other quarters^), 
are opposed by Gulli and Stavenhagen^), who by means of numerous 
analyses endeavour to prove that in good lemon oils the citral-content 
fluctuates between 7 and 7,3 per cent. In estimating the citral by means 
of the bisulphite method, Gulli and Stavenhagen have but rarely 
found oils of lemon containing less than 6,5 per cent, aldehyde. 
In this connection we wish to say that it is as a matter of fact 
impossible to make absolutely reliable statements on this subject, because, 
as we have shown in all cases ^), not one of the methods for estimating 
the citral-content in lemon oil, which have up to now been recom- 
mended, gives sufficiently accurate results. And in view of the fact 
that citral is only present in lemon oil in very small quantities, the 
accuracy of these results is a matter of the highest importance. 
For this reason we ourselves must decline to give any guarantee 
whatever with regard to the quantity of citral present in the oil of lemon. 
In giving an opinion on terpeneless oil of lemon. Parry ^), as 
evidence of the good quality of the oil, states that the citral isolated 
from it did not contain any trace of methyl heptenone, and that for 
this reason an admixture of lemongrass citral was out of the question, 
as the latter always contains methyl heptenone. This conclusion is 
^) The Chemist and Druggist 62 (1903), 476. 
2) The Chemist and Druggist 63 (1903), 277. 
^) The Chemist and Druggist 63 (1903), 341. 
^) The Chemist and Druggist 63 (1903), 401. 
^) Report April 1900, 24; October 1900, 26, 
^) Pharm. Journ. 70 (1903), 42. 
