Newsgroups: sci.chem
From: hoey@zogwarg.etl.army.mil (Dan Hoey)
Date: 11 Jun 92 21:27:18 GMT
Subject: Sodium Iodide content of Tincture of Iodine

For water purification, the rec.backcountry FAQ Panel 9 says:

>Also avoid tincture of iodine, which contains more sodium iodide than
>pure iodine; sodium iodide has no disinfectant properties.

Now tincture of iodine is supposed to be a solution of iodine in
alcohol; NaI if present is an impurity.  I imagine that Wilkerson's
"Medicine for Mountaineering", from which this statement has been
taken, is simply mistaken.

Does anyone have a reference for the amount of NaI that can be present
in tincture of iodine?  Or has any reader actually measured it?

Note that I'm not taking issue with the lack of disinfectant
properties of NaI, but with the amount of it in iodine tincture.

Tangentially, my vague recollection is that iodine added to a solution
of NaI dissolves and becomes colorless.  What is the reaction here, or
am I just mistaken?  This is not particularly relevant to the question
of NaI in tincture of iodine, except that it would probably mean that
such a mixture would be colorless.

Dan
Hoey@AIC.NRL.Navy.Mil