Travel Reference
In-Depth Information
Tincture of Iodine
Tincture of iodine is useful for water disinfection only because it is so readily available.
In industrialized nations such as the United States, tincture of iodine would be particularly
valuable when a major disaster, such as an earthquake, has resulted in contamination of
municipal water supplies and the water cannot be boiled because electrical power has been
interrupted and gas lines have been broken.
The major disadvantages of iodine tincture are its taste and its iodide component. Many
have found the iodine taste imparted by the tincture to be much stronger than that of other
preparations containing similar quantities of iodine. The U.S. Pharmacopeia (USP) stand-
ard solution is 2 percent iodine and 2.4 percent sodium iodide in 50 percent ethanol. (Dif-
ferent concentrations are also sold as “tincture.”) The iodide has no disinfectant activity
and increases total iodine intake.
Tincture of iodine resists freezing. Also, it can be used to disinfect skin, but aqueous
solutions are just as effective for that purpose and do not sting. Addition of 0.5 ml of a 2
percent solution to a liter of water provides an iodine concentration of 1.0 mg/l. The tinc-
ture must be stored in glass bottles.
Chlorine Disinfection
The effectiveness of chlorine for water disinfection is well documented. However, the
disinfectant action of chlorine is pH sensitive, and if organic residues are present, chlorine
combines with ammonia ions and amino acids to form chloramines, which release chlorine
slowly and inconsistently.
AlthoughmostmunicipalwatersystemsinNorthAmericausechlorineasadisinfectant,
free chlorine levels in the water must be constantly 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 or chlorine bleaches, are unstable and of questionable reliability.
(Manufacture of Halazone was discontinued in 1989.) Hypochlorous acid and chlorine di-
oxide are available in stable forms and are reliable.
Chlorine Preparations
Liquid Bleach (Sodium Hypochlorite)
Most liquid bleach preparations for home laundry are 5 percent sodium hypochlorite
solutions, which could disinfect water effectively, at least theoretically. Laboratory studies
toevaluate theeffectiveness ofsuchagentshavenotbeencarried out.Inaddition, thesolu-
tions are very unstable, which renders them problematic for wilderness water disinfection
becausemuchofthechlorineislostasthesolutionsloshesaroundwhilebeingtransported.
Solid or powder beach preparations are not available in a form that allows an appropriate
quantity for water disinfection to be easily determined.
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