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Diss Factsheets
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EC number: 201-782-8 | CAS number: 87-90-1
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
![](https://chesar.echa.europa.eu/o/diss-blank-theme/images/factsheets/A-REACH/factsheet/print_physical-and-chemical-properties.png)
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Reliability:
- 3 (not reliable)
- Rationale for reliability incl. deficiencies:
- other: The paper measured pKa1 only and references values from other studies.
- Reason / purpose for cross-reference:
- reference to same study
- Principles of method if other than guideline:
- The paper reports some titration and spectrometric studies which allow estimation of independent constants. pKa 1 was determined only for cyanuric acid.
- GLP compliance:
- no
- Remarks:
- Predates GLP
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 7
- Remarks on result:
- other: temperature not reported
- No.:
- #2
- pKa:
- 10.6
- Remarks on result:
- other: temperature not reported
- No.:
- #3
- pKa:
- ca. 13
- Remarks on result:
- other: temperature not reported
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- study well documented, meets generally accepted scientific principles, acceptable for assessment
- Principles of method if other than guideline:
- The equilibrium constants relating to the hydrolysis of chloroisocyanurates have been measured spectrophotometrically. The results have been used to calculate the concentration of hypochlorous acid under various conditions in swimming pools treated with chloroisocyanurates and cyanuric acid.
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 6.8
- Temp.:
- 23 °C
- No.:
- #2
- pKa:
- >= 10 - <= 11
- Temp.:
- 23 °C
- No.:
- #3
- pKa:
- > 11
- Temp.:
- 23 °C
- Conclusions:
- The lowest pKa of cyanuric acid was found by titration to be 6.80 and the two higher values of pKa were in the region 10-11.
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- study well documented, meets generally accepted scientific principles, acceptable for assessment
- Principles of method if other than guideline:
- The experimental determination of the dissociation constants was made by differential spectrometric titration.
- GLP compliance:
- no
- Remarks:
- Study predates GLP
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 6.88
- Remarks on result:
- other: temperature not stated
- No.:
- #2
- pKa:
- 11.4
- Remarks on result:
- other: temperature not stated
- No.:
- #3
- pKa:
- 13.5
- Remarks on result:
- other: temperature not stated
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Well described paper
- Principles of method if other than guideline:
- The pH dependence of the ultravioalet absoprtion spectra of cyanuric acid has been attributed by previous workers to dissociation in alkaline solution, however the limited available spectral range doe not permit a full study or interpretation of the changes in spectra due to the various charged species. The paper is concerned with the ultraviolet spectra, extended to 1880 Ǻ of solutions of the cyanurate species, both chlorinated and unchlorinated. The interpretation of the spectra is augmented by a study of the spectra of barbital (5, 5-diethyl barbituric acid) which may form in aqueous solution as many as three species with net charge 0, 1- , 2-.
- Dissociating properties:
- yes
- No.:
- #3
- pKa:
- ca. 13
- Remarks on result:
- other: temperature not reported
- Conclusions:
- The value of pK 3 of cyanuric acid was etimated from spectral changes to be about 13.
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Reliability:
- 3 (not reliable)
- Rationale for reliability incl. deficiencies:
- other: Ionization constants for cyanuric acid are reported .
- Principles of method if other than guideline:
- Spectrophotometrically determined ionization constants are reported for cyanuric acid
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 6.5
- Remarks on result:
- other: temperature not reported
- No.:
- #2
- pKa:
- 10.6
- Remarks on result:
- other: temperature not reported
- Conclusions:
- Values for pKa of 6.5 and 10.6 are reported for cyanuric acid
Referenceopen allclose all
The pH dependence of the ultraviolet absorption spectra of aqueous solutions of cyanuric acid and its chlorinated derivatives is attributed to dissociation leading to four species containing the cyanuric nucleus with net charge 0, 1 -, 2- and 3 -. Chlorination of cyanuric acid results in more diffuse spectra because several species of a given net charge may exist. At pH 14 the spectra of these solutions are essentially identical regardless of degree of chlorination and the principal organic ion present is the triply charged cyanurate. The value of pK3 of cyanuric acid was estimated from spectral changes to be about 13.
Description of key information
Several sources of literature are available which provide the dissociation constant of cyanuric acid as follows:
pKa1: = 6.5-7.0
pKa2: = 10 - 11
pKa3: ~13
Key value for chemical safety assessment
- pKa at 20°C:
- 6.5
Additional information
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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