26 
ON THE OIL OF MONARDA, 
ART. VII. — ON THE OIL OF MONARDA (HORSE-MINT.) 
By A. E. Arppe. 
The oil of Monar da punctata, which is officinal in the United 
States, separates readily into an eleeoptene and stearoptene* 
The first forms a yellowish-red fluid, which possesses the odour 
of thyme, and passes over when distilled with water of a bright 
yellow colour. The oil, thus purified and freed from water, 
boils at 435° F., when it becomes of a darker colour. As it 
cannot be assumed that this oil, the boiling-point of which ap- 
proaches so closely to that of the stearoptene, was obtained 
perfectly free from the latter, no safe conclusion as to its com- 
position can be expected from the analysis, which yielded 86.41 
per cent. C, 9.85 H, and 3.74 O. Exposed to the air, or 
placed in contact with substances containing much oxygen, it 
very easily changes to a resin, becoming brown and thick, and 
exhibits on analysis a considerable decrease in the amount of 
carbon. 
The stearoptene forms large crystalline fragments, which 
are coloured yellowish by the adherent fluid oil, and the odour 
of which has a striking resemblance to that of thyme. It can 
be obtained perfectly colourless by pressure between blotting 
paper, and quite pure by distillation either alone or with water. 
When submitted alone to distillation, the product solidifies in 
the recipient immediately, and forms very distinct crystals of 
remarkable lustre, which retaiu the above-mentioned odour 
and have an acrid burning taste. It leaves on distillation a 
small quantity of a brown resinous mass, which is soluble in 
alcohol. When the crystals thus obtained are distilled with 
water, they melt to an oil, and appear to undergo some change, 
as during ebullition the oil floating on the water becomes 
brownish ; however, it distils over entirely, and the residuary- 
water, which is wholly destitute of smell, has only a faint 
brownish tint. The distillate floats as a colourless oil on the 
