LABIATE 243
"belongs to the variety eriantha. The Bussian oil is stated to be derived
from the Mentha micrantha."
It has the following characters :—
Specific gravity.. 0-930 to 0'955
Optical rotation.. + 15° „ + 25°
Refractive index.. 1'4810 „ 1-4865
Pulegone .... not less than 80 per cent, (sulphite method)
The oil is soluble in 1/5 to 2*5 volumes of 70 per cent, alcohol. On
fractional distillation not more than 5 per cent, distils below 212°, and
from 212° to 216° at least 80 per cent, will come over.
The principal constituent of the oil is the ketone pulegone, which,
in very fine specimens, may be present to the extent of over 90 per cent.
According to Tetry
l
there are also present Z-limonene, dipentene, men-
thol, and menthone.
A Eussian pennyroyal oil, distilled from Pulegium micranthum has
been examined by Butlerow
2
many years ago. It had a specific gravity
Q'934. It commenced to boil at 202° and distilled principally at about
227°. He stated that the principal constituent had the formula G 10 H 16 0,
so that it was probably pulegone.
American pennyroyal oil is distilled from a herb indigenous to North
America, Hedeoma pulegoides. The oil is principally distilled in North
Carolina, Ohio, and Tennessee. The dried leaves yield about 3 per cent.,
.and the leaves and stalks together about 1/5 per cent, of essential oil.
The oil has the following characters:—Specific gravity 0925 to 0-940
Optical rotation + 18° „ + 35°
It is soluble in 2 volumes of 70 per cent, alcohol.
The oil contains pulegone, up to the extent of about 30 per cent.
According to Kremers
3
the oil contains two other ketones, one of which
is apparently menthone, and the other he has termed hedeomol, which
boils at 168° to 171° and forms an oxime melting at 41° to 43°. He
also identified formic acid, acetic acid and isoheptylic acid in traces.
Barrowcliff
4
has recently examined this oil. The oil used in this
investigation possessed the following characters: ^150/1500 = 0'9297;
OD + 25° 44' in a 1-dcm. tube; soluble in twice its volume of 70 per
cent, alcohol. It was found to consist of: (1) an undetermined phenol,
in very small amount; (2) Z-pinene; (3) Z-limonene; (4) dipentene, all
of these terpenes being present in only small amount; (5) l-methyl-3-
cycZohexanone about 8 per cent.; (6) pulegone, about 30 per cent.;
(7) Z-menthone, and (8) d-isomenthone, identical with the dextro-rota-
tory constituent of Beckmann's " inverted menthone "; the amount of
these two menthones constituting about 50 per cent, of the oil; (9) a
sesquiterpene alcohol, about 2 per cent.; (10) esters of formic, acetic,
octoic, decylic, and salicylic acids, and the ester of a dibasic acid of the
probable formula C 8 H 14 O 4 , together with formic, butyric, octoic, and
•decyclic acids in the free state; all these esters and acids being present
only in small amount.
Barrowcliff does not appear to confirm the presence of any ketone
-corresponding with Kremer's hedeomol.
1
Bull. Soc. Chim., iii. 27 (1902), 186. Jahr. d. Chem, (1854), 594.
Amer. Jour. Pharm., 59 (1887», 535. Jour. Chem. Soc., 91 (1907), 875.