Potassium hydroxide
This Product Safety Summary is intended to provide a general overview of the chemical substance in
the context of ICCA Global Product Strategy. The information in the Summary is basic information
and is not intended to provide emergency response, medical or treatment information. In-depth
safety and health information can be found in the (extended) Safety Data Sheet (e)SDS for the
chemical substance .
General Statement
Pure potassium hydroxide is a solid at room temperature and is manufactured from potassium
chloride by electrochemical means. Pure potassium hydroxide is a strongly alkaline substance (high
pH) and therefore it is corrosive and hazardous to human health. The substance is used in large
amounts in a variety of industries and is commonly found either as a solution in water or as a solid.
Chemical Identity
Name: potassium hydroxide
Synonyms: caustic potash, potash lye
CAS number: 1310-58-3
Molecular formula: KOH
Use and Applications
Potassium hydroxide has many different functions and uses. It is primarily used as an intermediate in
industrial manufacturing processes, such as the manufacture of fertilisers, potassium carbonate or
other potassium salts, and organic chemicals. It is also used in the manufacture of detergents and in
alkaline batteries. Small-scale uses include drain cleaning products, paint removers and degreasing
agents.
Physical/Chemical Properties
Pure potassium hydroxide is a solid at room temperature, though it is often sold as a liquid. The
appearance of the substance and some physical and chemical properties are mentioned in the table
below.
Property
Physical state
Colour
Density
Melting temperature
Boiling temperature
Molecular weight
KOH solid (90%)
Solid
White
2.044 g/cm3 (20 °C) (fused
solid)
406 °C
1327 °C
56.1 g/mol
KOH aq. solution (50%)
Liquid
Colourless
1.5 g/cm³
6 °C
145 °C
n.a.
Potassium hydroxide is a strong alkaline substance that dissociates completely in water into the
potassium ion (K+) and hydroxide ion (OH-). The dissolution in water generates heat, so a vigorous
reaction can occur when potassium hydroxide is added to water. The vapour pressure of the
substance is very low and the melting point is high. Potassium hydroxide solutions attack aluminium
and its alloys, giving off hydrogen gas. It can be neutralised with acids (e.g. hydrochloric acid) giving
the potassium salts of the acids, which are usually pH neutral and non-corrosive.
Human Health Safety Assessment
Potassium hydroxide is a strongly alkaline hydrophilic substance and therefore solid potassium
hydroxide is highly corrosive. It reacts with fat and can cause irreversible damage to any site of
contact with the body (for example skin or eyes). Solutions of potassium hydroxide in water at
concentrations above 0.5% (w/w) are irritating at points of contact and, at higher concentrations,
the solutions can be corrosive. Potassium hydroxide does not cause skin allergies.
Because of the corrosive properties of potassium hydroxide, its ingestion can be fatal. Under normal
conditions of handling and use, potassium hydroxide in solution will dissociate into its constituent
ions and, if ingested, will not be systemically available in the body as such. Furthermore, potassium
hydroxide and its ions are not carcinogenic, genotoxic or toxic to the reproductive system,
Environmental Safety Assessment
The environmental hazard of potassium hydroxide is due to the fact that it will raise the pH. A high
concentration in water will result in toxic effects for aquatic organisms e.g. fish. However, a low
concentration in water will not result in effects because the potassium hydroxide will be neutralized
by other substances present in water (for example dissolved carbon dioxide, organic acids) and thus
the pH will not increase.
Because potassium hydroxide is neutralized in the environment, the substance is not persistent and
it will not accumulate in organisms or in the food chain.
Exposure
Consumer
Potassium hydroxide is rarely found in consumer products. It can be found in some floor or wood
stripping products, oven or drain cleaners and other cleaning products; though, typically, the
analogous substance sodium hydroxide is used. The instructions on the label of all products should
be read and followed carefully to ensure safe use.
Worker
Because potassium hydroxide has many different functions and uses, it is extensively used in the
chemical industry and by different categories of professional users.
The grade of potassium hydroxide that is manufactured and used in industrial plants is usually
corrosive and, therefore, automated and closed systems are foreseen to prevent direct contact. In
such situations, the potential for workers to be exposed to the substance is very low. For the
professional applications, as for any irritating or corrosive product, appropriate personal protective
equipment should be used. Workers should consult the manufacturer’s Safety Data Sheet to obtain
specific advice.
Environment
The environmental hazard of potassium hydroxide is due to the fact that it will raise the pH. Because
there is legislation for the pH control of waste water and surface water in many countries, a
significant pH increase of the aquatic environment (e.g. a river or a sea) is not expected as a
consequence of the manufacture or use of potassium hydroxide. Therefore, no significant effects of
potassium hydroxide on the aquatic environment are expected.
Emissions into the air are also not a concern because potassium hydroxide will be rapidly neutralised
due to the natural presence of carbon dioxide in the air.
Regulatory Information
The substance was reviewed in 2004 under the OECD (Organisation for Economic Co-operation and
Development) high production volume (HPV) chemicals program. This is a global program to
evaluate the hazards of chemicals. In 2010, potassium hydroxide was registered under the European
Union REACH Regulation EC/1907/2006 and the substance was found to be safe for the uses
identified.
Classification and Labelling
The substance is subject to harmonised classification and labelling under the EU Classification
Labelling and Packaging (CLP) Regulation EC/1272/2008. The main elements are given hereafter:
Skin corrosion
category 1A
H314
Causes severe skin burns and eye damage
Acute toxicity
category 4
H302
Harmful if swallowed
The hazard statement “causes severe skin burns and eye damage” is applicable to concentrations in
chemical products of 2 % w/w or higher. The substance is classified as skin corrosive category 1A for
concentrations ≥ 5% and classified as skin corrosive category 1B for concentrations ≥ 2 and <5%. In
both cases the hazard statement H314 should be applied. Between 0.5 and 2 % the following
classifications and corresponding hazard statements are applicable:
- Skin irritation category 2, Causes skin irritation (H315) and
- Eye irritation category 2, Causes serious eye irritation (H319).
The European industry has decided to classify potassium hydroxide as corrosive to metals (H290;
May be corrosive to metals).
Conclusion
Potassium hydroxide is used in large amounts in industrial and professional applications and to a
lesser extent in consumer products. The handling of this hazardous substance has shown to be safe
when care is taken during use and provided that the given instructions are carefully followed.
Contact Information within Company
For further information on this substance or product safety summaries in general, please contact:
Xxxxx Xxxxx at xxxxxx@xxxxx.com or visit our website at www.xxxx.com.
Euro Chlor (www.eurochlor.org), the European chlor-alkali manufacturers association is a useful
repository of information regarding potassium hydroxide and can be contacted at
eurochlor@cefic.be.
Additional information on the ICCA global product strategy can be found here:
http://www.icca-chem.org/en/Home/ICCA-initiatives/global-product-strategy/
Date of Issue
xx/xx/xxxx
Revised
xx/xx/xxxx