SCIENTIFIC AND OTHER NOTES ON ESSENTIAL OILS. 13 
been eliminated by high-pressure steam. The difference of the two values corresponds 
to the depression caused by the volatile oil, from which the oil content may be easily 
calculated. On distilling the comminuted seeds according to the directions laid down 
by Beckmann, the unpleasant fact was noticed that the oil was decomposed in part. 
Zijlstra proved this by determining the refractory index of mixtures of limonene and 
carvone of known composition, before and after distillation (Beckmann’s method), when 
considerable differences were found. This test was made with the Universal Refracto- 
meter of Abbe, for which purpose but a few drops of oil are necessary. Moreover, 
more than but a few drops are not obtained from the distillation of the 5 grams of 
Seed used after Zijlstra’s method. By means of a table the carvone content may be 
read off easily from the value for np,po. 
From caraway seed originating from different districts in Holland, oils were 
obtained, after Beckmann’s distillation method, which showed very low figures for 
carvone, i.e., as low as from 7.5 to 25 p.c., which must be attributed to above-mentioned 
decomposition. By shortening the duration of distillation, and by using a little cylinder 
made of copper gauze instead of a tube of filtering paper as a receptacle for the 
distillation material, and finally by closing the little cylinder with a lid of the same 
material instead of a cotton-wool plug, Zijlstra succeeded in carrying out the distillation 
of carvone-limonene mixtures without an alteration in the refractory index becoming 
noticeable. From one and the same parcel of caraway seed, 27.0 p.c. of carvone were 
obtained after Beckmann’s method, as against 51.5 p.c. after Zijlstra’s modified method. 
The carvone content ascertained by determining the refractory index is invariably a 
little too low, but the differences are constant. 
| In the course of distillation a grey, emulsion-like mass collects in the condensing 
tube. This mass may possibly contain some fat oil (fixed oil). It must not be allowed 
to get into the distillate, as this would give rise to incorrect results. From caraway 
seed collected in 1910 in the Haarlem district, 4.65 p.c. of oil were obtained in this 
manner, showing 47.5p.c. of carvone. As regards the particulars of the method 
employed, we must refer readers to the original treatise. 
The author also examined 25 samples of caraway seed of the 1910 crop and 
found oil contents varying from 3.75 p.c. to 5.32 p.c.; the carvone percentage ranged 
between 47 up to 54.5p.c. Wild caraway seed collected in Holland contained 5.75 
and 6.72 p.c. of oil. It cannot be said with any degree of certainty to what causes 
these differences in oil and carvone percentages have to be attributed. It could, however, 
be proved by cultivation experiments that the distances from furrow to furrow exert 
a decided influence on the yield and oil percentage. For this purpose the author used 
Dutch caraway seed which contained 4.17 p.c. of oil showing 55.5 p.c. of carvone. 
The result of the experiments will be shown in the following table: — 
Method of planting planted Oil content cet oe oie 
A) Distance from furrow to furrow 30 cm., thickly 4.89p.c. 51.5 p.c. 21.4 
B) s 30 ;,.-. thinly 5.14 ,, 02.0335 15.5 
C) 9 60) .. thickly, 9:03: ,, D0.0n; 21.4 
D) i 60 ,, thinly 544 ,, 53 Ole 12.2 
This table will show that the oil percentage of the harvested seed was greater 
than the oil percentage of the seed used for sowing. It is surprising that the yields 
of A and C are identical, although the number of caraway plants with C was only 
half that of A. 
