8 BULLETIN 372. U. S. DEPARTMENT OF AGRICULTURE. 
EXTRACTION OF THE THYMOL. 
The oil of horseniiiit distilled from plants grown in Florida con- 
sists of phenols to the extent of 70 to SO per cent, and these phenols 
consist almost entirely of thymol, there being present also very sinall 
quantities of carvacrol. The nonphenol portion of the oil consists 
largely of cyniene, which acts as a solvent for the thymol and pre- 
vents complete crystallization. It is therefore necessary to separate 
these two compounds as a preliminary step in the extraction of the 
thymol. 
Since the two main constituents have a widely different boiling 
point, cymene boiling at 175° to 176° C. and thymol at 232° C. under 
normal pressure, almost complete separation can be secured by frac- 
tional distillation. The method devised for the separation is as fol- 
lows: The crude oil is distilled in a proper retort of copper, which is 
fitted with an efficient fractionation column, the one used in these 
experiments with the best results being the Hempel form. Dis- 
tillation is carried on slowly and the portion of the oil coming over 
below 215° C. is set aside. The temperature is then raised slightly 
and the fraction distilling over between 215° and 240° C. is secured. 
The residue in the retort is a thick, tarlike mass and so far as known 
is of no value. 
Practically ail the thymol is now contained in the second fraction, 
which consists of a rather heavy, slightly yellow liquid. The quan- 
tity of thymol contained in the first fraction should not be large if the 
process has been carried on carefully, but may run as high as 25 to 
30 per cent. This fraction is now redistilled under the same condi- 
tions as before, and the second fraction secured between 215° and 
240° C. is placed with the first one secured at this temperature and 
the residue discarded. 
The total fractions secured between 215° and 240° C. are allowed 
to cool in a shallow container and a small crystal of thymol is added 
to start crystallization. Within a few minutes a heavy crop of 
crystals will be secured. After standing over night the crystals 
are separated from the mother liquor by means of a centrifuge, 
and the crystals are washed with water while the centrifuge is run- 
ning at full speed and then dried by continued running of the cen- 
trifuge for three to five minutes. 
If cooled in a freezing mixture or by setting hi a cold place, the 
mother liquor will deposit another crop of crystals, but if a very large 
quantity of mother liquor is present it indicates that a considerable 
portion of the lower boiling fractions was not removed. It should, 
therefore, again be distilled in the same manner as before and the 
fraction secured between 215° and 240° C. should be treated in the 
manner previously described. 
