The chemical structure of chlorine dioxide is
shown below:
@O=Cl=O@
The conversion factor for chlorine dioxide in air at
20 °C and 101.3 kPa is 1 ppm = 2.8 mg/m3
.
Additional physical/chemical properties are
presented on the International Chemical Safety Card
(ICSC 0127) reproduced in this document.
At room temperature and pressure, the natural form
of chlorine dioxide is a gas that is unstable, highly
reactive (an oxidizing agent), and explosive. Consequently,
very few toxicological studies are available that
relate to the gaseous form. Some studies have been
conducted via the oral route using aqueous solutions of
chlorine dioxide. Several of these studies were conducted
using “stabilized aqueous chlorine dioxide,”
sometimes by maintaining a constant pH using sodium
carbonate and sodium hydrogen carbonate. However, it
is recognized that this would effectively lead to the
formation of aqueous sodium chlorite (which can
subsequently generate chlorine dioxide by acid displacement).
These studies are felt to be less relevant
than those using stabilized aqueous chlorine dioxide and
are not summarized in this review. The reasons for this
are that chlorine dioxide dissolves discretely in water
(i.e., it does not dissociate into ions), forming a solution
of around pH 5 or less, whereas an aqueous solution of
sodium chlorite has a different, ionized composition and
a pH of approximately 8. The explosive nature of this
substance has limited the concentration of chlorine
dioxide in aqueous solutions to a maximum of about 1%
w/v.