SPECIFIC MINERAL IRRITANTS.
IODINE AND IODIDE OF POTASSIUM.
IODINE is obtained from kelp (the ash of marine plants) and is a bluish
black scaly substance. It strikes an intense blue color with starch, and
when heated gives off an irritating purple vapor. It likewise imparts a
yellowish-brown stain to the skin (which may be removed by liquor
potassae) and mucous membranes, and slowly corrodes these tissues.
Iodine is an active poison, although its effects are variable. Some
constitutions are violently affected by two or three grains, whereas
others are uninjured by ten or twenty. Iodine is commonly employed in
medicine in combination with potassium (iodide of potassium). Of this
substance very large doses may be given (thirty grains or more, three
times a day) in tertiary syphilis, with none but good effect.
The _symptoms_ of poisoning by iodine consist of an acrid taste,
tightness about the throat, epigastric pain, vomiting, and purging,
especially if much has been taken. In a case which came under
observation, a man took an ounce of the compound tincture of iodine, in
mistake for a purgative draught. He was immediately seized with an
intense burning pain in the throat and epigastrium, and vomiting,
followed by great thirst, headache, and syncope. The vomiting was
encouraged, large quantities of arrowroot given, starch enemata
administered, and in twelve hours all the symptoms had disappeared,
leaving him in a state of exhaustion, from which he recovered in a few
days.
In chronic poisoning (iodism) there are signs of irritation of the
alimentary canal, often a measly eruption, ptyalism, running from the
nose and eyes, mental and bodily depression, and loss of flesh. Nothing
leads to the belief that it causes absorption of the testicles or mammae,
as is often asserted.
The _post-mortem appearances_ would be those due to an irritant poison,
namely, inflammation and softening of the stomach; the mucous membrane
being detached in different parts, and stained of a yellow color.
The _treatment_ should consist in the encouragement of vomiting, and
the free administration of amylaceous fluids, as gruel, arrowroot,
boiled starch, &c. This should be continued until the matters vomited
are of their natural color; for as long as any iodine remains they will
be rendered blue, iodide of starch being formed.
The crystals _of iodide of potassium_ are white cubes, very soluble in
water, and permanent in the air; though when impure they have a
yellowish tinge, and are deliquescent. In a few instances this valuable
medicine appears to have given rise to troublesome symptoms, even when
administered in small doses. Mr. Erichsen has reported a remarkable
case, in which five grains produced coryza, conjunctivitis, difficulty
of breathing, and other serious effects, promptly ceasing with the
discontinuance of the medicine. The _treatment_ must consist in emptying
the stomach by emetics or the stomach-pump, and administering starchy
diluents.
_Tests._ 1. Iodine may be readily detected by the blue color it gives to
starch.
Iodide of potassium gives the same when the iodine is set free by an
acid, such as sulphuric acid.
2. It also forms a scarlet precipitate with perchloride of mercury; and
3. It gives a yellow precipitate with acetate of lead.