REACTION BETWEEN IODINE AND THE ESSENTIAL OILS. 203 
REACTION BETWEEN IODINE AND THE ESSENTIAL OILS. 
By G. W. Patterson, M. D., 
Resident Physician of the Northern Dispensary. 
Having had occasion, recently, to prepare an ointment of Iodide 
of Sulphur, I was surprised to find on adding a drop of oil of berga- 
mot to the iodide previously pulverised, that a rapid interchange 
of elements ensued, accompanied with an evolution of the violet 
vapor of iodine, and the odor of sulphur. Upon subsequently ex- 
perimenting with other essential oils, I found that oil of juniper, 
savine, caraway, valerian, and lemon, produced a similar effect 
when added to that iodide. I furthermore ascertained, that none 
of the other iodides were perceptibly affected by the essential oils. 
On adding oil of lemon, bergamot and turpentine, to iodine alone, 
a phenomenon ensued resembling that produced when iodide of sul- 
phur was acted upon. 
I do not know that this incompatibility between iodine and the 
volatile oils has heretofore been noticed, and although it may be 
considered of no great practical importance, still it is something 
interesting.* 
It happens occasionally, that although certain medicinal agents 
are chemically incompatible with each other, nevertheless the 
medical quality desired is not lost by such combinations, as may be 
instanced by the collyrium which was at one time much employed, 
and which consisted of sulphate of zinc, acetate of lead, and wa- 
ter. The mistura ferri comp. of our Pharmacopoeia, is also an in- 
stance of the kind referred to. 
But when substances are combined, capable of undergoing such 
change as to render the combination unfit to meet the therapeuti- 
cal indication of a case, the physician must be disappointed, and 
confidence in medicine destroyed. 
*[Note by Editor. — The reaction between iodine and the volatile oils is 
noticed by Liebig, {Chimie Orgaiiiqve, tome, ii p. 309, 1842,) where he re- 
marks, " All the essential oils put in contact with iodine, produce a kind 
of explosion, in which the oils yield hydrogen to the iodine at the same time 
that a part of the iodine takes the place of the eliminated hydrogen." It 
is this sudden evolution of gas that causes the explosion, whilst the heat 
consequent upon the reaction, vaporizes a portion of the iodine. M. Zeller 
(Jahrbuch fur Praktische Pharm., Juli, 1849,) has taken advantage of this 
