Registration Dossier
Registration Dossier
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EC number: 215-181-3 | CAS number: 1310-58-3
Endpoint summary
Administrative data
Description of key information
Additional information
Potassium hydroxide is a strong alkaline substance that dissociates completely in water to K+ and OH-. In the majority of natural waters pH levels are between 6 and 10, which illustrates that OH- is a widely occurring chemical in nature. Also K+ is widely found in natural waters. Atmospheric emissions in the form of aerosols are rapidly neutralized by carbon dioxide as occurs with other bases (US EPA, 1988) and the salts will be washed out by rain. For this reason potential atmospheric emissions of KOH are considered of no concern. (OECD SIDS KOH, p.3)
High water solubility and low vapour pressure indicate that potassium hydroxide will be found predominantly in aqueous environments. The substance characteristics imply KOH will not adsorb on particulate matter or surfaces and will not accumulate in living substances (OECD SIDS potassium hydroxide, 2002). Significant emissions to the terrestrial environment are not expected during normal handling and use of KOH. Small terrestrial emissions will be neutralized by the buffer capacity of the soil. For this reason the environmental assessment can be limited to the aquatic compartment. (OECD SIDS KOH p.3)
Because KOH does occur in the environment as K+ and OH- a separate environmental assessment of both the potassium and the hydroxyl ion is needed.
An addition of KOH to an aquatic ecosystem may increase the pH depending on the buffer capacity of the receiving water. In general the buffer capacity is regulated by the equilibrium between CO2, HCO3- and CO32-:
CO2 + H2O * HCO3- + H+ (pKa1 = 6.35)
HCO3- * CO32- + H+ (pKa2 = 10.33)
The use of KOH could potentially result in an aquatic emission of KOH and it could locally increase the potassium and the pH in the aquatic environment.
The pH of effluents is normally measured very frequently, can be adapted easily and these effluents are commonly neutralised, and therefore a significant increase of the pH of the receiving water is not expected.
Emissions of potassium originating from the use of potassium hydroxide are small compared to other sources (natural and antropogenic) of potassium. KCl is a very large volume fertiliser (global production of 24 million tons K in 1989).
(see discussion in KOH SIDS Environmental Exposure and Fate)
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