stantly monitored to ensure they are adequate
for disinfection. Monitoring is not practical in
the wilderness or in developing countries.
Furthermore, chlorine compounds that have
been advocated for wilderness water disinfec-
tion, such as Halazone (which has not been
manufactured for fifteen years) or chlorine
bleaches, are unstable and of questionable re-
liability.
Most bleaches for home laundry use are
five percent sodium hypochlorite solutions,
which could disinfect water effectively. How-
ever, the solutions are very unstable, which
renders them unsuitable for wilderness water
disinfection because much of the chlorine is
lost as the solution sloshes around while being
transported. Solid or powder beach prepara-
tions are not available in a form that allows an
appropriate quantity for water disinfection to
be easily determined.
If liquid bleach is used for water disinfec-
tion, the standard procedure is to add two
drops to a liter of water with a temperature
above 60º F or 16º C and allow it to stand for
thirty minutes. If the water is colder, it should
be allowed to stand for forty-five minutes.
(For iodine the comparable times are ten and
twenty minutes, and cold water is 40º F or
5ºC.) If a slight odor of chlorine is not present
at that time more should be added.
Preparations such as SafeAqua.com use a
chlorine-based system that employs a different
approach. Initially far more chlorine is added
to the water than is needed for disinfection
(superchlorination). In the presence of exces-
sive chlorine pH inactivation or binding by
organic material are not significant. After the
water has been disinfected, the chlorine is
driven off.
(The first such preparation was the Sierra
Water Purifier. The writer was able to find
references to a change in name to "Sanitizer"
but could not find the product in any sup-
plier's website.)
These systems are much more suitable for
disinfecting relatively large quantities of wa-
ter -- five to ten gallons or twenty to forty
liters -- than the one or two liters that would
be carried in a backpack. The thirty percent
hydrogen peroxide used to drive off the chlo-
rine by Sierra Water Purifier is caustic. (It is
used in cosmetic dentistry to bleach teeth!
Ninety-nine percent H
2
O
2
is used for fuel for
the thruster rockets that control the position-
ing of spacecraft. ) Some individuals have
found they get the solution on their fingers
every time they use it, and that it produces a
burning sensation that lasts thirty to sixty
minutes. The skin may be blanched, although
no permanent injury is produced.
This procedure should be reliable; the
presence of a "strong smell of chlorine"
should be unmistakable. Additionally, the sys-
tem is small, light weight, and relatively sim-
ple, although two compounds must be added
to the water instead of one. It is more expen-
sive than the iodine based systems, but still is
relatively cheap. Hydrogen peroxide, if used
to drive off the chlorine, imparts a delightful
"sparkle."
A zinc brush can be used to remove the
chlorine instead of hydrogen peroxide or other
agents. Since zinc catalyses the remove of
chlorine instead of reacting with the halide, it
is not used up and can last indefinitely.
MSR MIOX PURIFIER
In the fall of 2003 MIOX Corporation
(www.MIOX.com), in association with Moun-
tain Safety Research (MSR), released a new
chlorine-based water disinfection system for
individuals. Various much larger units that
