POISONING BY ARSENIC USED EXTERNALLY. 79 
this effect was, however, so little apparent, that upon the 
same evening the places had dried up. 
We have already cited in our Journal so great a number 
of analogous facts, that it is not necessary to state here, that 
these extraordinary effects, in other respects rare, are the 
consequences of some individual predisposition, which will 
be met with by even the most careful practitioners. 
ART. XVL— REPORT MADE TO THE SOCIETY OF MEDI- 
CAL CHEMISTRY UPON A NOTE ADDRESSED TO IT 
BY M. GUYOT, A PHARMACEUTIST OF PARIS, ENTI- 
TLED "OF THE DECOMPOSITION OF ESSENTIAL OILS 
BY IODINE." 
Gentlemen: 
M. GuYOT, in the note addressed to you, has examined 
with more care than has hitherto been done, the action of 
iodine, both with and without heat, upon certain essential oils. 
He has discovered that many of them, as for instance, the oils 
of lemon, turpentine, naptha, and juniper, react violently and 
instantaneously when brought in contact with iodine at the 
ordinary temperature, and that others, on the contrary, pro- 
duce a reaction at the end of a period more or less prolonged; 
in this second category are placed the oils of mint, sage, la- 
vender, absinthium, &c. &c. 
Upon distilling the solutions of iodine in the essential oils 
of turpentine and savin, M. Guyot has observed that from 
the first impression of heat throughout the whole time of the 
operation a vivid reaction goes on, with a very abundant dis- 
engagement of hydriodic gas, and that finally, there remains 
in the retort an abundant residuum of carbon. 
The formation of so large a quantity of hydriodic acid has 
