ON THE ACTION OP SAL AMMONIAC, ETC. 
195 
ART. XXXVIII. — ON THE ACTION OF SAL AMMONIAC ON 
IODIDE OF POTASSIUM, AND UPON A PECULIAR MODE OF 
EXTERNAL USE OF THIS SALT. By M. Vogel de Munich. 
M, Breslau, Chief Physician to the King, who uses 
extensively the mineral water of Heilbrow, in which I 
found, in 1S25, iodide of soda in notable quantity, has em- 
ployed for some time the iodide of potassium in a peculiar 
manner as I have had occasion to witness. 
M. Breslau, employs a powder composed of iodide of potas- 
sium and sal ammoniac, which he causes to be enclosed in fine 
linen, and applied to the affected part. 
As I remarked that the lined bag containing this powder, 
and applied to the neck of a young person, had acquired, after 
a few days, a brown color, this phenomenon attracted my at- 
tention, and caused a desire to know what change had taken 
place in the two salts; I therefore undertook a series of ex- 
periments, with the view of ascertaining the cause. 
When we triturate together eight parts of sal ammoniac 
and one part of iodide of potassium, equally well dried, (for it 
is in these proportions that the salts are used by M. B.) am- 
monia is disengaged, and turmeric paper placed near the 
mixture becomes brown. This takes place with the iodide of 
commerce, which is usually feebly alkaline; but if we use 
iodide of potassium,which has been purified by repeated crystal- 
lizations, the disengagement of ammonia is almost wholly 
avoided. 
The mixture of sal ammoniac and iodide of potassium, in 
the above proportions, is perfectly colorless, and preserves its 
whiteness for an indefinite time, if kept from contact of air 
in close vessels. 
When we moisten this mixture, either that recently pre- 
pared or which has been kept for some time, with a weak so- 
lution of starch, it does not become blue, from whence it fol- 
lows, that in a recent mixture as well as one which has been 
well preserved, there is no free iodine. 
