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EC number: 205-861-8 | CAS number: 156-62-7
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 2000-03-23 until 2000-03-24
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 112 (Dissociation Constants in Water)
- Deviations:
- no
- Qualifier:
- according to guideline
- Guideline:
- EPA OPPTS 830.7370 (Dissociation constants in water)
- Deviations:
- no
- Qualifier:
- according to guideline
- Guideline:
- other: EEC Directive 94/37, Section 2.9.4 (of 22 July 1994)
- Deviations:
- no
- GLP compliance:
- yes (incl. QA statement)
- Dissociating properties:
- no
- Conclusions:
- Cyanamid F1000 does not dissociate in water.
- Executive summary:
The titration method, one of the possible experimental methods for determination of the dissociation constant (pKa), described in the OECD test guideline 112, was used in this study for pKa determination of the test item, Cyanamid F1000.
The pKa of Cyanamid F1000 could not be calculated because a dissociation reaction was not observed.
Aqueous solutions (approx. 0.005 mol/L) of Cyanamid F1000 have pH value of 6.3. They were titrated with 0.01 mol/L NaOH solution to test its acidic properties. There was no turning point in the titration curve, as it would be observed when an acid is titrated with a base. This result confirms the expectation that Cyanamid F1000 does not dissociate in aqueous solutions with pH values of 6 to 9. pH values > 9 were not tested since it is known from the literature that Cyanamid F1000 dimerises to dicyandiamide at pH values of 8 to 9.5.
Conclusion: Cyanamid F1000 does not dissociate in aqueous solutions with pH values of environmental relevance.
- Endpoint:
- dissociation constant
- Type of information:
- read-across from supporting substance (structural analogue or surrogate)
- Adequacy of study:
- key study
- Justification for type of information:
- Available experimental data for cyanamide are used in a read-across approach for the assessment of calcium cyanamide:
For detailled description where read across is used/recommended and where it is preferrable to refain from read across, please see section 13.2 "read across justification for environmental endpoints" and "Scientific rationale for not using cyanamide as read-across substance for calcium cyanamide on toxicological endpoints" - Reason / purpose for cross-reference:
- read-across source
- Dissociating properties:
- no
- Conclusions:
- Cyanamid F1000 does not dissociate in water.
Upon dissolution in water calcium cyanamide is fast transformed to hydrogen cyanamide. Therefore, available data for the Dissotiation of hydrogen cyanamide in water are used in a read-across approach for the assessment of calcium cyanamide. - Executive summary:
The titration method, one of the possible experimental methods for determination of the dissociation constant (pKa), described in the OECD test guideline 112, was used in this study for pKa determination of the test item, Cyanamid F1000.
The pKa of Cyanamid F1000 could not be calculated because a dissociation reaction was not observed.
Aqueous solutions (approx. 0.005 mol/L) of Cyanamid F1000 have pH value of 6.3. They were titrated with 0.01 mol/L NaOH solution to test its acidic properties. There was no turning point in the titration curve, as it would be observed when an acid is titrated with a base. This result confirms the expectation that Cyanamid F1000 does not dissociate in aqueous solutions with pH values of 6 to 9. pH values > 9 were not tested since it is known from the literature that Cyanamid F1000 dimerises to dicyandiamide at pH values of 8 to 9.5.
Conclusion: Cyanamid F1000 does not dissociate in aqueous solutions with pH values of environmental relevance.
This information in used in a read-across approach in the assessment of the target substance. For justification please refer to the section "Conclusion".
Referenceopen allclose all
- Aqueous solutions (approx. 0.005 mol/L) of Cyanamid F1000 have a pH value of 6.3. They were titrated with 0.01 mol/L NaOH solution to test its acidic properties. There was no turning point in the titration curve, as it would be observed when an acid is titrated with a base. This result confirms the expectation that Cyanamid F1000 does not dissociate in aqueous solutions with pH values of 6 to 9. pH values > 9 were not tested since it is known from the literature that Cyanamid F1000 dimerises to dicyandiamide at pH values of 8 to 9.5.
- The evaluation of the titration results was performed according to A. Albert & E.P. Sergeant (Ionization Constants of acids and bases, Wiley, inc. New York, 1962) in which the guideline refers to.
- Aqueous solutions (approx. 0.005 mol/L) of Cyanamid F1000 have a pH value of 6.3. They were titrated with 0.01 mol/L NaOH solution to test its acidic properties. There was no turning point in the titration curve, as it would be observed when an acid is titrated with a base. This result confirms the expectation that Cyanamid F1000 does not dissociate in aqueous solutions with pH values of 6 to 9. pH values > 9 were not tested since it is known from the literature that Cyanamid F1000 dimerises to dicyandiamide at pH values of 8 to 9.5.
- The evaluation of the titration results was performed according to A. Albert & E.P. Sergeant (Ionization Constants of acids and bases, Wiley, inc. New York, 1962) in which the guideline refers to.
Description of key information
Upon dissolution in water calcium cyanamide is transformed to hydrogen cyanamide. Therefore, the dissociation behaviour is independent from the test material (calcium cyanamide vs. hydrogen cyanamide). Test data on hydrogen cyanamide can thus be used by way of read-across.
The pKa of hydrogen cyanamide (Cyanamid F1000) could not be calculated because a dissociation reaction was not observed (in aqueous solutions with relevant pH values of 6 to 9). Accordingly, in the environmentally relevant pH range of 6–9 the acid-base equilibrium of the cyanamide system is entirely shifted towards the protonated form (hydrogen cyanamide).
For detailled description where read across is used/recommended and where it is preferrable to refain from read across, please see section 13.2 "read across justification for environmental endpoints" and "Scientific rationale for not using cyanamide as read-across substance for calcium cyanamide on toxicological endpoints"
Key value for chemical safety assessment
Additional information
The titration method, one of the possible experimental methods for determination of the dissociation constant (pKa), described in the OECD test guideline 112, was used in this study for pKa determination of the test item, Cyanamid F1000.
The pKa of Cyanamid F1000 could not be calculated because a dissociation reaction was not observed.
Aqueous solutions (approx. 0.005 mol/L) of Cyanamid F1000 have a pH value of 6.3. They were titrated with 0.01 mol/L NaOH solution to test its acidic properties. There was no turning point in the titration curve, as it would be observed when an acid is titrated with a base. This result confirms the expectation that Cyanamid F1000 does not dissociate in aqueous solutions with pH values of 6 to 9. pH values > 9 were not tested since it is known from the literature that Cyanamid F1000 dimerises to dicyandiamide at pH values of 8 to 9.5.
Conclusion: Cyanamid F1000 does not dissociate in aqueous solutions with pH values of environmental relevance.
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