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IODINE.
437
violet color. Iodine is usually in the form of bluish-black crys-
talline scales, with a metallic lustre, a strong, peculiar odor and
a hot, acrid taste. It is slightly soluble in water, and soluble in
alcohol, ether, solution of chloride of sodium and a solution of
iodide of potassium.
Medical Properties and Action.—Iodine in small doses is alter-
ative, stimulant and tonic, and acts locally as an irritant, causing
redness, itching and desquamation ; exhaled in the form of vapor,
it excites cough and warmth in the air passages. Taken inter-
nally it excites a sensation of heat or burning in the stomach, and
in large doses is an irritant poison, inflaming the mucous mem-
brane of the stomach and causing superficial eschars. The in-
ternal use of the iodides gives rise to an eruption of acne, espe-
cially on the face, thighs and shoulders ; they have also anaphro-
disiac powers when long continued. The influence of the iodides
in producing iodism may be prevented by large drafts of water
being used during their administration.
The odor of iodine can be detected in the blood, brain and
muscles.
When combined with potassium its local irritant effect is di-
minished ; hence the preparation known as Iodide of Potassium,
Potassii lodidum (obtained by treating an aqueous solution of
potassa with iodine), is employed whenever the constitutional
effects of iodine are desired, as the iodide of potassium possesses
many advantages over iodine for internal use, such as being less
irritant, and for this reason may be administered in larger doses
and for a greater length of time ; it is also more soluble than
iodine alone, and when taken into the stomach is absorbed much
more rapidly. The formula is Ki, and it is in the form of white
crystals, of an acrid, saline taste. Some persons are peculiarly
susceptible to the influence of iodine, even small doses causing
unpleasant effects, such as headache, vertigo, derangement of the
digestive organs, etc.
Iodide of potassium, like iodine, produces a very decided effect
on the secretions, increasing them, and occasionally to the degree
of ptyalism. The antidote for poisoning by iodine is starch.
Therapeutic Uses.—Iodine and its preparations are valuable re-