ON THE ACTION OF SAL AMMONIAC, ETC. 
199 
the slow disengagement of iodine is effected by the sal am- 
moniac even when the iodide is totally exempt from the 
iodate. 
The large proportion of the sal ammoniac would appear to 
favor the disengagement of the iodine, in as much as the iodide 
is more minutely divided, and offers a large surface for the 
action of the moist air ; at least I have found that the libera- 
tion of iodine was slow in a mixture of two parts of sal am- 
moniac with one of iodide of potassium ; it is therefore pro- 
per to adhere to the above proportions of eight parts of sal 
ammoniac to one of iodide of potassium. 
The advantages for the practitioner to employ this mixture 
as an external application, consists principally in its con- 
venience, and in the successive disengagement of an active 
agent, such as iodine. As soon as the iodine is set free it 
may be absorbed by the affected part, without being exposed to 
the risk of applying too large an amount upon one point ? 
from which more or less serious inconvenience might result 
to the patient. 
Conclusions. 
It results from these experiments, 
1. That iodide of potassium mixed with sal ammoniac 
does not undergo any change by the contact of dry air. 
2. That the same mixture is decomposed by moist air, so 
as to form an iodide of ammonium, from which the iodine is 
successively liberated. 
3. That the oxygen of the air is not absorbed by this 
mixture, but the change is due to the decomposition of water, 
slowly absorbed from the atmosphere. 
4. That after the lapse of several months, the iodide of 
potassium is decomposed into iodide of ammonium, which 
volatilizes, setting iodine free, and into chloride of pot- 
assium which remains with the excess of sal ammoniac. 
5. That dry iodide of potassium, as well as crystallized 
iodide of lead, is partially decomposed by ether, which takes 
away a certain quantity of iodine. 
